Catalysts doi: 10.3390/catal16050459

Authors: Daniel Garstenauer Lukas Sallfeldner Ondřej Zobač Franz Jirsa Klaus W. Richter

Intermetallic compounds represent a highly promising class of materials for catalytic applications due to their tuneable structure, composition, and electronic properties. In this study, we report a series of carbon black-supported intermetallic Pt-Te and Pt-Zn nanoparticles synthesized via a novel and facile direct vapour–solid approach. Their catalytic performance toward the oxygen reduction reaction (ORR) in alkaline media was systematically investigated. Incorporation of Te or Zn into Pt/C significantly enhanced the intrinsic activity, as reflected by an increase in the limiting current density from −2.11 mA cm−2 for Pt/C to up to −2.94 mA cm−2 for Pt-Zn and −2.85 mA cm−2 for Pt-Te systems, while maintaining similar half-wave potentials of 0.79 V vs. RHE and onset potentials around 0.90 V vs. RHE. This work provides a direct comparison of two intermetallic systems prepared under identical conditions, demonstrating how composition and crystal structure determine the catalytic activity and selectivity in the ORR.

Catalysts doi: 10.3390/catal16050460

Authors: Shaomeng Huang Yiqing Xu Feijian Jing Liping Wang Jiawen Sheng Qiongqiong He

In the process of pollutant degradation by activating peroxymonosulfate (PMS) with carbon-based Fenton-like catalysts containing Fe as the active site, the influence of Zn atoms on the system has rarely been studied. In this study, by regulating the introduction of Zn sources, Fe-Zn-C and Fe-C catalysts were successfully synthesized for activating PMS to degrade butyl xanthate (BX). The degradation experiment results showed that compared to the Fe-C system, the doping of Zn increased the degradation rate of BX in the Fe-Zn-C system by 10.66%, reaching 91.19% within 120 min. Moreover, by optimizing the reaction conditions, the highest BX degradation efficiency of 96.54% was achieved within 30 min. Through instrumental analysis, Fe and Zn elements were found to exist on the surface of the catalysts in the form of Fe2+Fe3+2O4 and ZnO crystals, and the catalytic oxidation reaction was dominated by non-free radical pathways, including 1O2 and direct electron transfer pathways. No free radicals were produced during the reaction, and it was speculated that Zn atoms played the role of an electron bridge in the reaction system, mediating electron transfer and enhancing catalytic performance through their synergistic effect with Fe. Comprehensive stability evaluation indicated that Fe-Zn-C ensures continuous catalytic activity and ecological safety with a low dissolution rate in aqueous solution. This study provides a new approach for the design of Fenton-like catalysts and the induction of non-radical pathways.

Catalysts doi: 10.3390/catal16050457

Authors: HanBit Lee JongHyeon Lee HwanHee Choi HwaYong Lee YoungHee Kim

Ammonia (NH3) emissions from livestock facilities pose significant environmental challenges, particularly under high-humidity conditions where conventional adsorption efficiency significantly declines. This study investigates the photocatalytic removal of NH3 using TiO2-coated zeolite LTA supports (3A and 4A) under relative humidity (RH) levels typical of farm environments. The composites were synthesized via controlled dip-coating cycles and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer–Emmett–Teller (BET) analyses. At 55% RH, zeolite 3A exhibited higher NH3 removal efficiency than zeolite 4A, owing to its smaller pore size and superior intrinsic adsorption selectivity. However, adsorption-only systems underwent rapid deactivation over repeated cycles. While TiO2 coatings enhanced the photocatalytic activity of both supports, zeolite 3A composites showed a more pronounced decline in efficiency over time. In contrast, at 95% RH, the TiO2-coated zeolite 4A achieved superior photocatalytic efficiency and operational stability. This performance is attributed to the 4A framework’s greater water uptake and faster diffusion kinetics, which promoted the generation of hydroxyl (•OH) and hydroperoxyl (HO2•) radicals under UV-A irradiation. These findings suggest that while TiO2–zeolite 3A is effective at moderate humidity, TiO2–zeolite 4A is more robust for high-humidity livestock environments, providing a sustainable strategy for effective NH3 emission control.

Catalysts doi: 10.3390/catal16050458

Authors: Giacomo Seccacini Martina Fattobene Leonardo Suraniti Paola Russo Mario Berrettoni

The performance of a Mayenite-supported nickel-based catalyst were investigated by using an in-house-designed, assembled and set-up chemical pilot plant, which was developed to provide experimental insights relevant to industrial scale up. In particular, the proposed heterogeneous catalytic system was structured in mm-sized spheres and tested in a large-scale experiment, in a fixed-bed reactor for the CO2 methanation process, and the results were compared with the output achieved with a Ni/alumina catalyst produced by an analogous route as the benchmark. The obtained findings highlighted the effective potential of the Mayenite structure supporting metallic active sites in promoting CO2 reduction under the selected operating conditions (450 °C, 4 bar), along with long-term stability and high CH4 selectivity. Moreover, the available experimental equipment was optimized to achieve accurate estimations of amounts of reaction by-product , as confirmed by the optimal agreement with the mass balance retrieved from the measured gaseous outlet composition. Such an achievement, notable for a large-scale chemical plant, plays a capital role in terms of industrial applications due to the critical impact of residual carbon and water in establishing the viability of innovative catalyst systems for the CO2 recycling process.

Catalysts doi: 10.3390/catal16050456

Authors: Jianhui Yi Zi Wen Qing Jiang

Electrochemical nitrogen reduction reaction (NRR) is a sustainable and environmentally friendly method for ammonia synthesis, offering a promising alternative to the Haber–Bosch method. Despite its considerable potential, NRR is still plagued by a scarcity of efficient catalysts. Metal–nitrogen–carbon (M–N–C) catalysts exhibit unique advantages in achieving excellent NRR performance. Theoretical calculations are crucial in understanding and guiding the design of M–N–C catalysts. Herein, we summarize the theoretical progress and rational designs of M–N–C catalysts for NRR. The fundamental mechanisms of NRR are introduced, and the activity, selectivity, and stability exhibited by the M–N–C catalysts are analyzed in depth. Additionally, several design strategies for M–N–C catalysts are provided, including adjusting the central metal atoms, regulating the coordinative environments, and applying computational data-driven approaches to optimize the structures of M–N–C catalysts. Finally, a summary and outlook of M–N–C catalysts for NRR are given.

Catalysts doi: 10.3390/catal16050455

Authors: Yanliang Yang Yaoru Du Yue Luo Ying Duan Dong Sui Yunmeng Wang Xuechuan Lv Tianliang Lu

Catalytic hydrodeoxygenation (HDO) of aromatic aldehydes represents a core research direction in the efficient utilization of lignin. In this study, a cost-effective catalyst was constructed by incorporating rich lattice defects into Ni nanoparticles. The catalyst was synthesized via a uniform precipitation method, employing urea as the precipitant. By introducing aluminum nitrate during the precipitation process, nickel was effectively segregated to inhibit its growth and the generation of well-crystallized, defect-free Ni nanoparticles, thereby generating a substantial quantity of defective Ni nanoparticles with abundant lattice defects. The catalyst was characterized using XRD, TEM, HRTEM, EDS line and mapping scanning, XPS and H2-TPD, confirming the formation of Ni nanoparticles with a narrow size distribution of ~5 nm with numerous lattice defects. The hydrodeoxygenation of vanillin was employed to evaluate the catalyst’s activity, with investigations into the effects of Al content, solvents, temperature, H2 pressure, and reaction time. The reaction was successfully conducted at 363 K in water. The catalyst demonstrated excellent hydrodeoxygenation activity across a series of other aromatic aldehyde compounds. Cycle experiments confirmed the catalyst’s stability, maintaining its activity over at least five consecutive uses.

Catalysts doi: 10.3390/catal16050454

Authors: Xiudan Tao Xiaohan Yang Fufen Li Yuqing He Chenhui Liu Zhengjun Li Nianhua Dan

Oxygen vacancies play a crucial role in modulating the chemical and catalytic properties of metal oxide catalysts. Herein, quercetin was used as a green reducing agent to prepare Cu-doped MnO2 (Cu-MnO2) composite catalysts with varying Cu doping levels via an ultrasonically assisted strategy. The structure-activity relationships were systematically investigated using XRD, Raman, XPS, H2-TPR, and O2-TPD. Benefiting from optimized surface lattice defects induced by an appropriate Cu doping level, the Cu-MnO2-2 sample, which exhibited the highest oxygen vacancy concentration, achieved a HCHO removal efficiency of 99.2% for 1 ppm HCHO at room temperature (25 °C) and 50% relative humidity within 30 min. The enrichment of Mn3+, Cu+, and surface-adsorbed oxygen species (Oads) further corroborated the increased oxygen vacancy density, indicating that moderate Cu doping effectively promotes electron transfer and oxygen activation. After five consecutive cycles, the HCHO conversion remained above 96%. Post-cycling characterizations (XRD, FTIR, EDS, and XPS) confirmed the excellent structural and chemical stability of the catalyst, with the Mn3+ proportion and Cu+/Cu2+ ratio well preserved. In situ DRIFTS analysis revealed that surface-adsorbed oxygen and oxygen-vacancy-activated reactive oxygen species (ROS) are key factors in the efficient HCHO oxidation over the green Cu-MnO2-2 catalyst, promoting rapid conversion of intermediates and ultimately generating CO2 and H2O. This study provides a facile, low-cost, and green synthesis strategy for Cu-MnO2 composite catalysts for indoor, room-temperature HCHO abatement, offering new insights into the design of other composite catalyst materials.

Catalysts doi: 10.3390/catal16050453

Authors: Kantarattana Paramanurak Adriano Vignali Benedetta Palucci Fabio Bertini Kotohiro Nomura Simona Losio

The development of polyolefin from bio-renewables has been considered an important subject in terms of circular economy. In this study, exploring the possibility of β-myrcene (MY) incorporation in propene copolymerization has been studied in the presence of various catalysts: phenoxide-modified half-titanocene, Cp’TiCl2(O-2,6-iPr2-4-C6H3) [Cp’ = Cp* (C5Me5), Me3SiC5H4], and ketimide-modified half-titanicene, Cp’TiCl2(N=CtBu2) (Cp’ = Cp*, Cp). Among the complexes tested, the permethylated Cp* catalysts, Cp*TiCl2(O-2,6-iPr2-4-C6H3) and Cp*TiCl2(N=CtBu2), exhibited moderate catalytic activities in the copolymerizations, affording the copolymers up to 3 mol% MY incorporation. The other catalysts showed negligible activity in the attempted copolymerizations. The resulting copolymers were amorphous and possessed sole glass transition temperatures (Tg), suggesting uniform compositions; the Tg values decreased with increasing comonomer (MY) content, reaching values as low as −17 °C. The results introduce valuable insights into the structure–property relationships of myrcene-based copolymers and pave the way for the future designs of tailored molecular catalysts for the synthesis of biobased elastomers.

Catalysts doi: 10.3390/catal16050452

Authors: Jingang Zhao Guanchao Wang Taoyang Zou Yuekun Jing Fang Liu

While the petroleum industry undergoes structural adjustments in supply and demand alongside a green and low-carbon transition, water drilling mud generated during oil extraction poses severe environmental challenges. Consequently, addressing the solid waste pollution and disposal issues associated with drilling mud has become critical. In this study, ZSM-5 zeolite was synthesized using water drilling mud as a silicon and aluminum source, inexpensive n-butylamine as a template agent, and a combined approach of alkali-melting activation pre-treatment and seed-directed hydrothermal synthesis. By adjusting key parameters such as water content, template agent dosage, and seed addition, optimal synthesis conditions were determined. Based on these conditions, a series of ZSM-5 zeolites with varying silicon-to-aluminum ratios were synthesized. Characterization results from XRD, TEM, SEM, and N2 adsorption–desorption experiments revealed that all prepared samples exhibited high crystallinity, regular morphology, and high specific surface area. 27Al MAS NMR results indicated that almost aluminum species were located at the framework structures with four-coordination. In the 1,3,5-triisopropylbenzene cracking reaction, the conversion rate increased with decreasing silicon-to-aluminum ratio, consistent with variations in acid amount. These findings achieve high-value utilization of waste drilling mud, offering a novel pathway for low-cost synthesis of high-performance ZSM-5 zeolite. This breakthrough injects fresh momentum into the petroleum refining industry’s green sustainable development, fostering a win–win scenario that harmonizes ecological conservation with industrial profitability.

Catalysts doi: 10.3390/catal16050451

Authors: Hao Luo Qiao Dai Ting Mo Yunye Wang Chenghao Lei Meihong Wu Xuemei Liao

This study presents an approach for the “one-pot two-step” synthesis of 2,5-diformylfuran (DFF) from fructose using a metal-free phosphorus-doped carbon nitride (P-CN) catalyst. The bifunctional P-CN integrates P-O bonds for acid-catalyzed fructose dehydration to 5-hydroxymethylfurfural (HMF) and P-C/graphitic-N sites for selective aerobic HMF oxidation to DFF. The 10% P-CN catalyst achieved 91.5% DFF yield during the stepwise oxidation of isolated HMF under the mild conditions (1.5 MPa O2, 120 °C), while the “one-pot” cascade reaction yielded 63% DFF due to competing side reactions. Characterization revealed that P-doping enhanced porosity (883 m2/g surface area) and electronic properties, with graphitic-N facilitating O2 activation. P=O groups are hypothesized to mediate proton transfer from reactive substrates via hydrogen-bonding networks, thereby enhancing acid-catalyzed pathways. NH3-TPD and XPS confirmed tailored acid sites and P-N/C elemental synergism, while FT-IR demonstrated substrate adsorption via P=O/HMF-OH interactions. The catalyst retained stability over multiple cycles, demonstrating its practicality. This work advances biomass valorization by elucidating the dual-role design of nonmetallic catalysts, offering an eco-friendly alternative to conventional metal-based systems.

Catalysts doi: 10.3390/catal16050450

Authors: Shengxian Xian Jiurun Liu Qing Xu

Microwave-assisted pyrolysis (MAP) has emerged as a revolutionary technology for converting solid waste into high-value hydrocarbons. However, conventional pyrolysis and traditional single-function catalysts often face an inevitable “performance trade-off” involving severe mass transfer resistance, poor microwave absorption, and rapid coking. This review systematically summarizes the recent evolution of catalyst design toward advanced multi-site composites. It highlights the synergistic mechanisms of integrating microwave-responsive cores, hierarchical pore networks, and metal-acid bifunctional sites to achieve ultrafast localized heat transfer, targeted bond cleavage, and in-situ coking suppression. Furthermore, this paper critically examines current bottlenecks in scaling MAP to industrial levels. To address these challenges, we discuss emerging solutions, including hydrogen-enriched co-pyrolysis, non-destructive in-situ regeneration, and the integration of machine learning frameworks for intelligent process optimization.

Catalysts doi: 10.3390/catal16050449

Authors: Arif Savaş Samet Uslu Gonca Uslu Oğuzhan Der Ali Erçetin Ramazan Şener

The catalytic modification of combustion processes using nanoparticle additives has emerged as a promising strategy to improve fuel oxidation and reduce pollutant formation in compression ignition (CI) engines. In this study, the catalytic effects of nano-sized boron oxide (B2O3) on biodiesel combustion were systematically investigated. Jojoba oil, a non-edible and drought-resistant feedstock, was transesterified to produce second-generation biodiesel and blended with diesel fuel. Among the tested blends, J10 (10% biodiesel and 90% diesel) was selected as the base fuel blend due to its favorable combustion and emission characteristics. To explore catalytic enhancement mechanisms, B2O3 nanoparticles were introduced at concentrations of 25, 50, and 75 ppm. The high surface area and oxygen buffering capacity of B2O3 nanoparticles are expected to enhance oxidation reactions and promote radical formation during combustion. This catalytic effect contributes to improved combustion efficiency, as evidenced by a significant reduction in incomplete combustion products. Compared with diesel fuel (D100), HC emissions were reduced by up to 53.34%, while CO emissions decreased by 24.42–41.98% depending on the operating conditions and fuel blends. In addition, a noticeable improvement in combustion quality was reflected in the brake thermal efficiency (BTE), where variations of up to 11.61% were observed across different fuel blends. Response Surface Methodology (RSM) was employed to quantify the interaction between nanoparticle concentration and engine load and to identify optimal catalytic operating conditions. The optimal parameters were determined as 12.14 ppm B2O3 and 1.36 kW load, yielding a desirability of 0.7128. Under these conditions, the engine achieved a BSFC of 458.83 g/kWh and BTE of 22.01%, with emissions reduced to 0.041% CO, 14.29 ppm HC, and 346.44 ppm NOx. The results demonstrate that nano B2O3 functions as a combustion catalyst by enhancing oxidation pathways and improving fuel-air interaction, thereby increasing combustion efficiency and reducing harmful emissions.

Catalysts doi: 10.3390/catal16050448

Authors: Shaomeng Huang Jiawen Sheng Yiqing Xu Liping Wang Feijian Jing Qiongqiong He

1O2 has significant advantages over free radicals in Fenton-like reactions, but the induction of a single 1O2 reaction pathway is challenging and is often accompanied by free radical reactions and direct electron transfer pathways. In this study, Zn-O-C/N and Zn-S/O-C/N catalysts were synthesized by controlling the doping of the S element, and the single 1O2 reaction pathway was successfully induced. Furthermore, Zn-O-C/N performed better than the Zn-S/O-C/N system, with higher phenanthrene (PHE) degradation rates of 76.14% compared to 62.86%. And Zn-O-C/N can achieve a maximum degradation rate of 85.62% under the developed optimization condition. The characterization results revealed that the ZnO active sites are located on the surface of the Zn-O-C/N catalyst and participate in electron mediation together with C-N. ZnS was generated with the doping of S, speculating that a large amount of ZnS with low catalytic activity is generated and occupies the active sites, thereby inhibiting the catalytic activity. Additionally, only 1O2 was generated in the two systems, without the formation of free radicals and the occurrence of direct electron transfer reaction. However, the Zn-O-C/N catalyst has been proven to have strong stability and a low amount of dissolution, demonstrating environmental safety. This study confirmed the inhibitory effect of S on the activity of the Zn-O-C/N system and provided a synthesis strategy for the catalyst design, which can only induce the 1O2 reaction pathway.

Catalysts doi: 10.3390/catal16050447

Authors: Mani Sivakumar Ganeshraja Ayyakannu Sundaram Junhu Wang

The increasing presence of microplastics in the aquatic and terrestrial food chains calls for the need to come up with innovative and effective remediation approaches. Such innovations as zinc oxide (ZnO) structures and metal–organic frameworks (MOFs) are examined as the second generation of photocatalysts for degrading microplastics under sunlight. We will focus on the latest advances and discuss the structure of photocatalytic processes, their functioning under various light conditions, and their environmental impacts, especially environmental safety and ecotoxicity. ZnO structures are even better photocatalysts because they form reactive oxygen species (ROS) as good as other metal oxides. However, their possible cytotoxicity and the ability to generate oxidative stress require serious evaluation. MOFs, on the contrary, offer physicochemical properties, environmental safety, ecotoxicity, and environmentally friendly synthesis pathways, making them a worthy substitute. The review underscores the urgency of incorporating environmental safety and ecotoxicity into the design of photocatalysts, thereby unlocking their full potential while avoiding environmental or human health risks. Moving forward in the field of sustainable nanotechnology to remove microplastics will provide the way to come up with green innovations and hence guarantee the effectiveness of combating plastic pollution in long-term stability.

Catalysts doi: 10.3390/catal16050445

Authors: Sihui Song Chunting Li Sadaf Mutahir Muhammad Asim Khan Feng Yan

The catalytic reduction of toxic 4-Nitrophenol (4-NP) to valuable 4-aminophenol is highly important for environmental remediation. However, developing catalysts with high activity, good recyclability, and facile preparation remains challenging. Herein, Ag@Fe3O4 nanocomposites were controllably synthesized with a facile one-pot polyol method. By varying the Ag:Fe precursor ratio, the structure could be tuned from dense and porous core-shell to Janus architectures. The porous Ag@Fe3O4 nanoreactors (Ag:Fe-0.4) exhibited exceptional catalytic performance, achieving complete 4-NP reduction within 75 s, with an apparent rate constant (k) of 6.29 × 10−2 s−1, a normalized rate constant (kn) of 3742 s−1 mmol−1, and a TOF value of 1042 h−1. XPS results verified that the excellent activity originated from the porous structure and interfacial charge transfer from Ag to Fe3O4. The catalysts showed super-paramagnetism and could be reused for at least eight cycles with >95% conversion retained. It also displayed high efficiency in reducing diverse nitroaromatics and in natural water. This work highlights the significance of structural and electronic modulation, providing a scalable strategy for magnetically recyclable catalysts toward environmental remediation and heterogeneous catalysis.

Catalysts doi: 10.3390/catal16050446

Authors: Nadia ALHirbawi Amélie Enciso Juarez Michela Martinelli Savana R. Alt A. Jeremy Kropf Donald C. Cronauer Gary Jacobs

Sodium (Na) promotion of Ru/m-ZrO2 was investigated to elucidate how an alkali modification tunes selectivity in methanol steam reforming (MSR). H2-TPR/XANES/EXAFS show that Na increases surface basicity and strengthens Ru–O interactions, shifting RuOx reduction and H2 spillover to a higher temperature. DRIFTS reveals Na-induced red shifts of the formate ν(CH) band and changes in OCO vibrational splitting, consistent with weakening of the formate C–H bond and an altered binding geometry. CO2-TPD confirms a monotonic shift toward stronger basic sites with increasing Na concentrations. Under MSR conditions, Na selectively increases CO2 concentration at the expense of CO. At ~80% conversion and 325 °C, CO2 selectivity increases from 12.0% (unpromoted) to 16.2, 21.0, and 26.5% for 0.5, 1.0, and 1.8% Na, respectively; at ~300 °C and ~66–69% conversion, CO2 selectivity increases from 8.6% to 23.7% at 1.8% Na. Transient MSR experiments further show earlier and larger H2 evolution upon Na addition, corroborating the promotion of the dehydrogenation/decarbonylation route to CO2 + H2. We propose that Na increases basicity and modifies the Ru–support interface to favor formate dehydrogenation/decarboxylation, thereby increasing the H2 yield and lowering CO formation. Ru’s higher-energy, less occupied d-band stabilizes CO and oxygenated intermediates more strongly in the reforming environment, making the CO-forming pathway more resistant to suppression than on Pt.

Catalysts doi: 10.3390/catal16050444

Authors: Changchun Yan Zhiqiang Xu Dingming Xue Jiaqing Wang Xiaochen Lin Hao Zhou Bing Ma Houhu Zhang

Fe–carbon catalysts (FCCs) are extensively used for persulfate activation in advanced oxidation processes (PS-AOPs), an approach regarded as an efficient and cost-effective strategy for removing emerging contaminants (ECs). However, the quantitative structure–activity relationship between the degradation efficiency of ECs with diverse molecular characteristics and the microstructure of FCCs has not been clearly elucidated. This hinders the widespread practical implementation of FCCs. Herein, density functional theory (DFT)-derived molecular-descriptor-assisted machine learning models were employed to accurately predict the reaction rate constants for EC degradation in FCC-PS AOPs, mainly focusing on three aspects: performance prediction, operating condition optimization and mechanism interpretation. Additionally, DFT-derived descriptors are integrated with fabrication and operational parameters to facilitate the generative design of FCCs. The excellent fitting performance of the overall XGB model in predicting the reaction constants for EC degradation (Test R2 = 0.813) highlights the notable advantages of customized hyperparameter tuning for improving predictive accuracy. Subsequently, the submodels trained using different EC clusters (derived from t-SNE and K-means clustering methods) can offer specific strategies for selecting optimal parameters of FCC-PS AOPs that target ECs with distinct properties. The interpretability of the model was improved by using SHAP values and partial-dependence plots to clarify the internal relationships of the ML “black box”. Overall, a feasible and generalizable ML model is proposed to facilitate a paradigm shift in the inverse design of FCCs for the degradation of specific ECs.

Catalysts doi: 10.3390/catal16050443

Authors: Qi Wang Gongjie Hua Aiguo Gu Jie Zou Kuangfei Lin

Per- and polyfluoroalkyl substances (PFASs) in fluorinated firefighting wastewater (FFW), which are difficult to remediate using conventional technologies, represent a critical environmental hazard due to the extreme persistence and bioaccumulation potential of soil–groundwater systems. Niobium-supported boron-doped diamond (BDD) anodes were synthesized by microwave plasma chemical vapor deposition, and their performance in the electrochemical advanced oxidation processes (EAOPs) of FFW were systematically investigated. Under optimized conditions (100 mM Na2SO4 electrolyte with 100 mM peroxymonosulfate (PMS), current density of 33.3 mA/cm2, pH = 6), the BDD anode achieved near-complete mineralization, with 92.5% total organic carbon (TOC) removal and significant defluorination (77.5% F− release) within 240 min in simulated FFW-contaminated groundwater. For FFW-contaminated soil remediation, 90.2% TOC removal and 41.6% defluorination were achieved after 720 min under optimal treatment (water-to-soil ratio of 20:1). Quenching experiments and electron paramagnetic resonance (EPR) tests revealed that hydroxyl radicals (·OH) and singlet oxygen (1O2) were the predominant reactive species. Liquid chromatography–mass spectrometry/mass spectrometry (LC-MS/MS) analysis indicated that PFASs were removed by shortened carbon chains, ultimately mineralizing to CO2 and F−. Toxicity assessment using Vibrio fischeri luminescence demonstrated a reduction in toxicity (from 99.8% to 20.9%), confirming the effective detoxification of BDD-based EAOPs. This work establishes BDD-based EAOPs as a promising technology for eliminating PFASs in groundwater and soil, offering theoretical insights into EAOPs and engineering solutions for PFAS remediation.

Catalysts doi: 10.3390/catal16050442

Authors: Zhaocen Dong Meng Wang Yu Zhang Youtian Wang Zhijie Wu Yibo Zhou Haoxuan Zhang Meili Guan Xuezhong Gong Jianguo Tang

Photocatalytic oxygen reduction to hydrogen peroxide (H2O2) offers a promising route for sustainable chemical synthesis, yet the efficiency of carbon nitride-based photocatalysts is often limited by narrow light absorption and rapid charge recombination. Low-molecular-weight carbon nitride exhibits a favorable reduction potential but suffers from poor visible-light utilization, while π-conjugation extension and heteroatom doping are effective yet rarely combined within a single oligomeric framework. In this work, we report a low-temperature (400 °C) one-step copolymerization approach employing urea and terephthalonitrile to construct an oxygen-doped, benzene-bridged carbon nitride oligomer (O-B-CNO). Comprehensive characterization confirms the successful integration of both benzene rings and oxygen dopants into the oligomer backbone, with the former enhancing structural stability and the latter introducing active sites. The extended conjugation and oxygen incorporation synergistically modulate the electronic structure, leading to a narrowed bandgap, improved visible-light harvesting, and suppressed charge recombination. As a result, O-B-CNO delivers a photocatalytic H2O2 yield of approximately 3000 μM under visible-light irradiation, a 10-fold enhancement over the pristine oligomer, with optimal activity at neutral pH via the two-electron oxygen reduction pathway. The enhanced performance stems from the complementary functions of the two modifications: benzene rings promote electron delocalization and charge transport, while oxygen dopants serve as selective active centers for oxygen reduction. This work demonstrates a viable molecular engineering strategy for developing efficient carbon nitride photocatalysts for H2O2 production.

Catalysts doi: 10.3390/catal16050441

Authors: Esthela Ramos-Ramírez Norma Gutiérrez-Ortega Julio Castillo-Rodríguez Claudia Martínez-Gómez Israel Rangel-Vázquez Francisco Tzompantzi-Morales José María Solis-Murillo Javier Vallejo-Montesinos

Currently, the search continues for solutions for the treatment of water contaminated by toxic compounds such as chlorophenols that are used in the manufacture of pesticides, insecticides, and the paper industry, among others, and that are considered persistent in the environment, in addition to being extremely toxic, especially 2,4,6-trichlorophenol, which is potentially carcinogenic. In this work, the use of thermally activated Co/Fe hydrotalcites as photocatalysts is presented. The catalysts were characterized by differential thermal and thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, N2 physisorption, diffuse reflectance spectroscopy and photoluminescence. The catalysts were tested in the photo-assisted degradation of 80 mg/L of 2,4,6-trichlorophenol. The catalytic structures present are Co/Fe simple and mixed oxides. The results of the photocatalytic activity show that the materials have good photocatalytic activity with a degradation efficiency of 2,4,6-trichlorophenol, reaching a maximum capacity of 65% for oxides derived from hydrotalcites with a Co/Fe ratio of 2 and calcined at 500 °C, exceeding the activity shown by the reference catalyst, high-performance commercial titanium dioxide. The photocatalytic activity studied for the catalyst with the highest percentage of degradation is attributed to the presence of holes, as well as to the formation of oxidizing species such as superoxide and hydroxyl radicals that are determinants in the degradation mechanism.

Catalysts doi: 10.3390/catal16050440

Authors: Wenzhen Yang Xuefeng Jiang Ye Tu Na Jiao Mengting Jin

First-principles calculations are employed to systematically investigate the dynamic evolution from Al(Oh) to Al(Td) in zeolites induced by proton–cation exchange (Cu+, Li+, Na+, NH4+). The protons directly bonded to Al(Oh) are found to be essential for structural stability. Single cation exchange preserves the six-coordinated Al(Oh), while double exchange triggers spontaneous conversion to four-coordinated Al(Td), accompanied by stepwise detachment of two water molecules. Different cations exhibit variations in spatial occupation patterns and water-binding strength. The coordination effect of metal cations and the hydrogen bonding effect of NH4+ dominate the transformation of the aluminum coordination configurations. Protons directly bonded to Al(Oh) serve as strong Brønsted acid sites. Single exchange indirectly reduces the activity of adjacent protons, whereas double exchange eliminates Al–O–H bonds to stabilize Al(Td). This work reveals a cooperative mechanism among cation species, exchange number, water binding, and electronic coupling that controls the Al(Oh) to Al(Td) transformation, providing a theoretical basis for activating Al species and for designing high-performance catalysts with controlled acid site distributions via ion exchange.

Catalysts doi: 10.3390/catal16050439

Authors: Gaidong Sheng Yaxuan Wang Liang Lv Xilong Wang Yousheng Yin Yan Zhang Han-Pu Liang

Pt-based intermetallics are high-efficiency electrocatalysts for the hydrogen evolution reaction (HER) in proton exchange membrane water electrolysis (PEMWE). However, the synthesis of intermetallics usually relies on high-temperature annealing, which easily induces particle agglomeration and limits the improvement of catalytic performance. In this study, a synergistic strategy of spatial confinement and ordered structure regulation is adopted, and indene-derived mesoporous carbon (IMC) is used as the support to controllably synthesize the intermetallic Pt3Fe catalyst. The IMC support can anchor and spatially confine nanoparticles, thereby preventing particle sintering and agglomeration during high-temperature annealing. In 0.5 mol·L−1 H2SO4 electrolytes, the catalyst exhibits excellent catalytic performance: it achieves an overpotential of only 19.1 mV at a current density of 10 mA·cm−2, which is 9.4 mV lower than that of commercial Pt/C; its mass activity reaches 2.76 A·mgPt−1, 8 times that of commercial Pt/C. Chronopotentiometry measurements show negligible potential variation after 190 h of operation at 10 mA·cm−2. This strategy suppresses particle agglomeration through the spatial confinement effect of IMC and modulates electronic states via the ordered structure, providing a practical route for the scalable preparation of low-cost, highly active and high-stability Pt-based intermetallics for PEMWE applications.

Catalysts doi: 10.3390/catal16050438

Authors: Seong Yeop Han Bimo Tri Goutomo Dian Majid Il-Kyu Kim

Acid Black 1 (AB1), a recalcitrant disazo dye from the textile industry, poses a severe threat to aquatic ecosystems owing to its resistance to biological treatment. Although ferrate(VI) (K2FeO4) and plasma-based advanced oxidation processes have shown promise for dye remediation, the effect of treatment sequence on synergistic mineralization remains largely unaddressed. Nano-ferrate(VI) (nano-Fe(VI), K2FeO4) synthesized via the Solution Plasma Process (SPP) was integrated with Gliding Arc Plasma (GAP) in a sequential hybrid system, with nanoscale morphology and K2FeO4 composition confirmed by FE-SEM and EDS. pH, molar ratio, and temperature were systematically optimized for the standalone nano-Fe(VI) process, and synergistic performance was evaluated via Synergy Effect Factor (SEF) analysis. Optimization identified pH 7.0, [AB1]:[Fe(VI)] = 1:0.9, and 45 °C as optimal, achieving 90.24% decolorization within 12 min. The sequential nano-Fe(VI)–GAP configuration achieved the highest mineralization efficiency of 58.7%, outperforming standalone nano-Fe(VI) (36.0%), standalone GAP (16.0%), and simultaneous application (37.8%), with SEF values of 1.3 and 1.2 for mineralization and decolorization. This is the first study to quantify treatment sequence effects in a nano-Fe(VI)–GAP system via SEF analysis. The proposed system eliminates intermediate pH adjustment while achieving superior mineralization, offering a practical AOP framework for refractory textile wastewater treatment.

Catalysts doi: 10.3390/catal16050437

Authors: Pengcheng Feng Yue He Sen Wang Zhiwei Wu Tianfu Zhang Weibin Fan Mei Dong

The ethylene aromatization (ETA) reaction is a pivotal route for non-petroleum-based aromatics production, yet a systematic understanding of its thermodynamic constraints and kinetic modulation remains elusive. Herein, an integrated thermodynamic and kinetic study is presented to elucidate the temperature-dependent reaction pathways over metal oxide-modified HZSM-5 catalysts. Thermodynamic calculations reveal that while oligomerization, cyclization, and the hydrogen transfer (HT) pathway are exothermic, the aromatics-generating dehydrogenation (DH) pathway is endothermic. Crucially, despite the general thermodynamic penalty imposed by elevated temperatures on most elementary steps, the overall ethylene aromatization reaction retains a strong driving force, underscoring the dehydrogenation pathway as the thermodynamic and kinetic key to aromatic selectivity. Experimentally, it is demonstrated that modifying HZSM-5 with ZnO, Ga2O3, and ZnGa2O4 effectively tunes the Lewis-to-Brønsted acid (L/B) ratio. A strong linear correlation is established between the L/B ratio and the apparent activation energy, with a higher L/B ratio significantly lowering the activation barrier. This synergistic effect optimally promotes the dehydrogenation pathway, suppresses alkane by-product formation, and maximizes aromatic yield within an optimal temperature window of 470–520 °C. The findings provide a fundamental and practical framework for the rational design of high-efficiency ethylene aromatization catalysts and the optimization of process conditions via targeted acid site engineering.

Catalysts doi: 10.3390/catal16050436

Authors: Jinying Gao Jiaxin Ji Menglu Gao Ting Yue Meirong Huang

A-site defect engineering has been confirmed as an effective strategy for enhancing catalyst performance. Here, we develop a novel approach to synthesize A-site deficient perovskites by regulating alkali metal substitution and evaporation and further apply these materials for photocatalytic applications. Three representative perovskite oxides—La2Ti2O7, Na2La2Ti3O10, and Na0.5La0.5TiO3—were synthesized and then converted into perovskite oxynitrides with varying degrees of A-site defects (LaTiO2N, La0.67TiO2N, and La0.5TiO2N) through high-temperature ammonolysis. The photocatalytic water oxidation activity increased with the concentration of A-site defects, following the order: LaTiO2N < La0.67TiO2N < La0.5TiO2N, with a maximum enhancement of over 30 times. The performance boost was attributed to the facilitated interfacial electron transfer and improved charge separation caused by abundant A-site defects. These findings demonstrate that this strategy can successfully construct A-site deficient perovskites for highly efficient photocatalytic reactions, providing valuable insights for designing defect-engineered perovskite materials.

Catalysts doi: 10.3390/catal16050435

Authors: Margherita Gazzotti Fabrizio Medici Laura Raimondi Sergio Rossi

The combination of photochemistry with stereoselective catalysis has emerged as an effective strategy to achieve stereocontrol in light-driven transformations. Chiral phosphoric acids (CPAs) have recently attracted attention in this context due to their ability to activate substrates while providing a defined chiral environment. This minireview highlights recent developments in CPA-enabled asymmetric photochemical transformations, focusing on systems in which CPAs incorporate a chromophore on the chiral backbone or form light-absorbing CPA-substrate complexes that enable photoactivation without the presence of an external photocatalyst. The main catalytic strategies, mechanistic features, and current limitations are discussed.

Catalysts doi: 10.3390/catal16050434

Authors: Samar M. Mahgoub Abdelghafar M. Abu-Elsaoud Seham M. Hamed Ahmed A. Allam Saber A. A. Elsuccary Mahmoud M. Ghuniem Hend A. Mahmoud Vehaan Subramanian Rehab Mahmoud

Water contamination by arsenic(V) [As(V)] and Congo red (CR) dye poses concurrent threats to public health and aquatic ecosystems, particularly in regions where metallurgical and textile industries coexist. Developing a single adsorbent capable of simultaneously addressing these chemically distinct pollutants, while recovering value from the spent material remains an open challenge in sustainable water treatment. This study reports the synthesis and evaluation of a novel ternary MgZnFe-LDH/1,2,4-triazole composite (TM-LDH/TZ), engineered for the concurrent adsorptive removal of As(V) and CR, and the subsequent repurposing of the pollutant-loaded material as an electrocatalyst for the urea oxidation reaction (UOR). The composite was prepared via co-precipitation and triazole surface grafting, then characterized by FTIR, XRD, BET, TGA, FESEM, and HRTEM. Batch adsorption experiments examined the influence of pH, adsorbent dose, initial concentration, and temperature, with equilibrium data modeled through Langmuir, Freundlich, Temkin, and the statistically grounded Advanced Monolayer Model (AMM); kinetics were assessed using pseudo-first/second-order and Elovich models. Maximum Langmuir adsorption capacities reached 204.75 mg g−1 for As(V) and 499.72 mg g−1 for CR simultaneously at pH 5 and 25 °C, surpassing the majority of previously reported single-pollutant adsorbents. Elovich and pseudo-second-order kinetics confirmed chemisorption as the governing pathway for As(V) and CR, respectively, while AMM thermodynamic analysis verified spontaneous adsorption across all experimental conditions. The spent composite delivered a UOR peak current density of 184.67 mA cm−2 that is nearly twice that of the fresh material, with a reduced charge-transfer resistance of 1.19 Ω, and removal efficiency remained above 85% through three successive regeneration cycles. The bifunctional design, coupling high-capacity dual-pollutant removal with catalytic valorization of waste, positions TM-LDH/TZ as a circular-economy-aligned platform for advanced water remediation.

Catalysts doi: 10.3390/catal16050433

Authors: Gyungmin Kim Ben Nadeau Hua Song

The transition to renewable carbon resources has positioned lignocellulosic biomass as a key feedstock for sustainable fuel and chemical production; however, its intrinsic recalcitrance limits efficient conversion. Dilute acid pretreatment functions as a homogeneous Brønsted acid catalytic system that selectively depolymerizes hemicellulose and disrupts lignin–carbohydrate complexes, while competing with consecutive sugar dehydration reactions, thereby enhancing downstream processing. This review presents a feedstock-specific analysis of acid catalyzed biomass deconstruction across agricultural residues, woody biomass, and energy crops, with xylose yield employed as a kinetically and mechanistically relevant descriptor of catalytic performance. By correlating proton activity, reaction severity, diffusion constraints, lignin chemistry, and mineral interference with observed conversion behavior, the work establishes a structure–reactivity–performance framework for biomass dependent hydrolysis. Particular attention is given to competing dehydration and condensation pathways that reduce pentose selectivity and generate fermentation inhibitors. The analysis identifies optimal severity windows for maximizing catalytic efficiency while suppressing degradation reactions and provides guidance for feedstock-tailored pretreatment and next-generation acid catalytic systems and reactor configurations in integrated biorefineries.

Catalysts doi: 10.3390/catal16050432

Authors: Wenquan Sun Siqi Chen Yueqian Cheng Jun Zhou Kinjal Shah Yongjun Sun

Ce-Ni@WSA (WSA = water-resistant silica–alumina gel) ozone catalyst was prepared with an impregnation–calcination method using WSA as the support and characterized by SEM, XRD, BET, XRF, and XPS analyses. The operating conditions and reaction mechanism of the Ce-Ni@WSA catalytic ozonation of norfloxacin (Nor)-simulated wastewater were systematically studied. A data-envelopment analysis model (DEA-B2C) was then established to evaluate the catalytic ozonation process. Under the optimal conditions of initial pH 7.42 (raw water), ozone dosage = 0.4 g/L/h, catalyst-filling ratio = 5%, humic acid dosage = 0 mg/L, the removal rates of chemical oxygen demand (COD) and Nor reached 84.95% and 93.52%, respectively. Ce-Ni@WSA retained its high catalytic performance and mechanical strength after 50 cycles of repeated use. Mechanistic studies showed that •OH oxidation was dominant in the catalytic-ozonation system, and Nor can be degraded into small molecules through three different pathways and eventually mineralized. The DEA-B2C model analysis showed that the treatment cost was low and the catalytic efficiency was high under the optimal operating conditions.

Catalysts doi: 10.3390/catal16050431

Authors: Radu Mirea

The Fenton reaction remains one of the most widely investigated advanced oxidation processes for wastewater treatment due to its ability to generate highly reactive oxygen species capable of degrading persistent organic pollutants. However, classical homogeneous Fenton systems suffer from significant limitations, including narrow pH applicability, iron sludge generation, and poor catalyst reusability. In response, extensive research has focused on the development of heterogeneous and advanced Fenton-like catalysts aimed at overcoming these challenges while enhancing catalytic efficiency and operational stability. This review provides a comprehensive and critical analysis of the evolution of Fenton catalysis, from classical homogeneous systems to advanced materials, including nanostructured catalysts, carbon-based Fe–N–C systems, metal–organic frameworks, and single-atom catalysts. A unified evaluation framework is proposed, integrating key performance parameters such as catalytic activity, manufacturability, stability, and catalyst lifespan. Comparative analysis reveals that improvements in activity are often accompanied by trade-offs in cost and scalability, indicating that the most advanced materials do not necessarily provide the best practical performance. A life cycle-oriented perspective is incorporated, emphasizing catalyst reuse, lifespan, and iron leaching, and providing quantitative insight into cumulative catalytic performance. The results demonstrate that long-term efficiency is governed not only by intrinsic activity but also by durability and operational stability under realistic conditions. Finally, current challenges and future directions are discussed, including scalable synthesis, improved mechanistic understanding, and integration into hybrid treatment systems. This review bridges the gap between fundamental research and practical application by highlighting the importance of balancing performance, stability, and sustainability in the design of next-generation Fenton catalysts.

Catalysts doi: 10.3390/catal16050430

Authors: Chuan Long Yi An Bowen Xia Feifei Fang Jingjing Wang Chenyi Shao Yinglong Yu Haicheng Xiao Yanfei Wang

Proton exchange membrane water electrolysis (PEMWE) is currently limited by the sluggish kinetics and poor durability of the oxygen evolution reaction (OER). In this work, a structurally uniform IrB160-4 catalyst was synthesized through a simple, scalable one-pot aqueous method. This template-free method enables near-quantitative yields and gram-scale preparation, with products rapidly separated via simple filtration. The catalyst consists of uniform, nanoclusters self-assembled from highly crystalline ~3 nm Ir nanoparticles. The optimized catalyst exhibits superior OER activity over commercial Ir-Black. The assembled proton exchange membrane electrolyzer, utilizing a low anodic iridium loading of 0.5 mg cm−2, demonstrates excellent performance (2.0 A cm−2 @ 1.79 V) and high durability (>1500 h). This synthesis strategy provides a feasible method for achieving efficient and stable PEM water electrolysis for hydrogen production.

Catalysts doi: 10.3390/catal16050429

Authors: Guijun Li Ruoyang Du Caihong Jiang Xuhui Wei Binbin Jiang Qiuyan Cao Junwei Wang Xiaolong Zhou

Elemental mercury (Hg0) in coal-fired flue gas has become a focal yet challenging issue in mercury pollution control due to its high toxicity, bioaccumulation potential, and high volatility. There is an urgent need to develop a technology of Hg0 catalytic oxidation that is both low-cost and highly efficient. On the other hand, waste fluid catalytic cracking (WFCC) catalysts generated from the petroleum refining industry are classified as hazardous solid waste, necessitating effective harmless disposal and resource recovery. Herein, a composite support (A-P) was constructed by combining an activated WFCC catalyst (AFCC) with the natural mineral palygorskite, followed by the loading of VOx active species to prepare a Vx/A-P catalyst for Hg0 removal from flue gas. Moreover, the effects of the preparation process and conditions of the Vx/A-P catalyst on the Hg0 removal performance were systematically studied. This work aims to provide a theoretical basis and technical support for the development of low-cost, high-performance mercury removal catalysts, while also promoting the green recycling and value-added utilization of waste catalysts.

Catalysts doi: 10.3390/catal16050428

Authors: Jianlong Wen Yuan Yu Dongfeng Sun Yanning Qu Xiaoya Yuan Congcong Lin Jia Liu Yiyan Jiang Yunkun Yang Bingshe Xu

A layered bimetallic CoMo-LDH precursor was prepared on nickel foam via a hydrothermal method, and a 3D hierarchical flower-like nanosheet CoMoP/NF electrocatalyst with a crystalline–amorphous heterostructure was constructed in situ through low-temperature phosphidation. The water electrolysis performance was optimized by adjusting the Co/Mo molar ratio. The 3D hierarchical porous structure provides a large specific surface area and abundant active sites, and Mo doping effectively modulates the electronic structure. The catalyst exhibits superior HER performance with overpotentials of only 37 mV and 65 mV at 10 mA·cm−2 in acidic and alkaline media and shows a lower HER overpotential than commercial Pt/C at current densities above 426 mA·cm−2 in acidic conditions. Meanwhile, this catalyst delivers an OER overpotential of 729 mV at 500 mA·cm−2 in alkaline media and can operate stably for 50 h. The assembled two-electrode overall water splitting cell only requires 1.42 V at 10 mA·cm−2, outperforming Pt/CǁRuO2 (1.52 V). This work offers a promising strategy for designing low-cost and high-efficiency overall water splitting electrocatalysts for high-current-density applications.

Catalysts doi: 10.3390/catal16050427

Authors: Mohammad Saood Manzar Sally Mostafa Khadrawy Mohd Imran Karim Tanji Mukarram Zubair Hissah A. Alqahtani Bhagyashree R. Patil Essam Kotb Mohammed Abdul Aleem Qureshi Hassan A. Rudayni Ahmed A. Allam

In the current research, graphene and cellulose nanocrystals (CNCs) loaded with silver nanoparticles were synthesized using the hydrothermal method with different mass ratios (G:CNC:CS). The composite GC2 (1:0.2:0.2) (MIC = 6.1 µg·mL−1) and GC3 (1:0.3:0.3) (MIC = 1.8 µg·mL−1) exhibited the maximum antibacterial activity against Staphylococcus aureus subsp. aureus ATCC BAA-977 and Pseudomonas aeruginosa, respectively. The antibacterial performance underscores the complex interplay between the compositional attributes of GC2 and GC3, and the unique susceptibility profiles of different bacterial strains. The antibacterial mechanism was proposed to understand the antibacterial activity process. Ag+ cations and reactive oxygen species (ROS) formed with the composite materials are responsible for disrupting interactions with the bacterial cell wall via transmembrane proteins. Eriochrome Black T exhibited the highest photocatalytic degradation efficiency (~90% under UV), followed by Congo Red, which also showed substantial removal across all irradiation conditions. In contrast, Bisphenol A and tetracycline displayed comparatively lower degradation efficiencies, particularly under UV light. Overall, the degradation trend for all pollutants followed the order: UV > solar > visible irradiation.

Catalysts doi: 10.3390/catal16050426

Authors: Yankai Li Xu Feng Shuo Wang He Huang Qingrun Meng

In this work, various types of organosilanes were introduced into Sn-Si oxide through a simple aerosol process to yield synthesis precursors. Then, a series of Sn-Beta zeolites were successfully synthesized using a hydrothermal method in the presence of fluoride. The influence of amine groups (A, 2A, and 3A), the length of branched chains present in the organosilanes, as well as the use of dipodal silanization agents (B2A) on the morphology, pore structure, acidic properties, coordination state, and content of Sn species in the obtained Sn-Beta zeolite samples was investigated. Compared to the organosilane-free Sn-Beta (crystal size: 1.3 μm; Si/Sn = 119; Lewis acid density: 77 μmol·g−1), all monopodal organosilane-doped samples (Sn-Beta-A, -2A, and -3A) exhibited reduced crystal sizes (~0.9 μm) and increased specific surface areas (up to 502 m2·g−1 for Sn-Beta-2A). UV–Vis spectroscopy showed that Sn-Beta-2A (containing two amine groups) achieved the highest optical bandgap (4.68 eV) and the strongest suppression of extra-framework SnOx species (peak at ~269 nm), indicating the most isolated tetrahedral framework Sn4+ sites. This sample also delivered the highest Lewis acid density (225 μmol·g−1) and the best catalytic performance in the Baeyer–Villiger oxidation of cyclohexanone (39% conversion, TON = 106) and 2-adamantanone (37% conversion, TON = 101). By contrast, the dipodal organosilane (B2A) caused severe steric hindrance, yielding the lowest crystallinity (relative crystallinity 64%), Si/Sn ratio (158), Lewis acid density (38 μmol·g−1), and catalytic activity, despite forming a nanoaggregate morphology with high mesoporosity (V meso = 0.20 cm3·g−1). These quantitative results demonstrate that monopodal organosilanes with two amine groups optimally balance Sn incorporation and textural properties, whereas dipodal silanes hinder framework Sn entry. This study provides clear, numerically grounded guidelines for selecting organosilane functional groups to design high-performance Sn-Beta zeolites.

Catalysts doi: 10.3390/catal16050425

Authors: Wenjun Liang Ruifang Li Qianyu Tao Yuxue Zhu Running Kang Hongping Fang

Red mud (RM), a metal oxide-rich solid waste, was subjected to three different acid treatments to evaluate its catalytic performance in toluene oxidation. The acetic acid-modified red mud (HAC-RM) demonstrated excellent catalytic activity, achieving complete toluene conversion at 450 °C. XRD, XRF, N2-BET and SEM results show acetic acid treatment can effectively remove pore-blocking inert components such as Na2O and CaO, thus increased the Fe2O3 content, and significantly enhanced both the specific surface area and pore size of the catalyst. Furthermore, this modification enhanced reducibility and generated additional oxygen vacancies, verified by H2-TPR and O2-TPD, thereby improving the overall catalytic performance. In contrast, oxalic acid treatment under ultraviolet irradiation led to the formation of calcium carbonate via reaction with Ca2+ ions in RM, which resulted in reduced catalytic activity. To further enhance performance, MnO2 was loaded onto the modified HAC-RM via an impregnation method to develop a low-cost and highly active catalyst. Among the prepared samples, 20%MnO2/HAC-RM exhibited the highest catalytic efficiency, achieving 100% toluene conversion at 300 °C. XPS, H2-TPR, and O2-TPD results indicate the synergistic interaction between Fe2O3 and MnO2 facilitated electron transfer and enhanced surface oxygen mobility. Additionally, the catalytic oxidation mechanism of 20% MnO2/HAC-RM was elucidated. A detailed reaction pathway for toluene degradation is proposed by in situ DRIFT, as follows: toluene → benzyl alcohol → benzaldehyde/benzoyl peroxide → benzoate → CO2 and H2O. These findings are expected to contribute to the development of efficient, sustainable, and cost-effective catalysts for volatile organic compound (VOC) abatement.

Catalysts doi: 10.3390/catal16050424

Authors: Sylwia Gajewska Agnieszka Wróblewska Piotr Miądlicki Beata Michalkiewicz Luis A. Gallego-Villada Anna Fajdek-Bieda

The subject of the presented work was the study of the pathways of geraniol transformation during its oxidation with molecular oxygen in the presence of a natural Japanese volcanic clay mineral—mironekuton—used as a green heterogeneous catalyst. Prior to the catalytic tests, a comprehensive characterization of mironekuton was carried out using SEM, XRD, EDX, FTIR, and UV–Vis techniques. The catalytic experiments were aimed at establishing reaction conditions enabling effective geraniol conversion and controlling the distribution of valuable transformation products under solvent-free conditions. The influence of temperature (75–100 °C), catalyst content (0.5–5.0 wt%), and reaction time (15–360 min) was systematically investigated. The obtained results demonstrated that pristine mironekuton exhibits moderate activity and limited selectivity toward low-molecular-weight oxygenated derivatives of geraniol, such as 2,3-epoxygeraniol, 2,3-epoxycitral, and citral. Instead, dehydration, isomerization, and dimerization reactions play a significant role, leading to the formation of higher-molecular-weight products, particularly thunbergol and 6,11-dimethyldodeca-2,6,10-trien-1-ol. Sulfuric acid treatment of mironekuton results in a pronounced enhancement of catalytic activity and a substantial shift in product distribution. This effect is directly related to the increased surface acidity, which promotes dehydration–dimerization pathways over epoxidation, leading to thunbergol as the dominant product with high and reproducible selectivity, while epoxidation products are no longer detected. Kinetic modeling of the geraniol transformation process revealed that epoxidation steps are kinetically disfavored and that epoxide species act only as short-lived intermediates, whereas dehydration–dimerization pathways are kinetically preferred. Overall, the results indicate that acid-activated mironekuton functions as an efficient and environmentally benign heterogeneous catalyst, favoring selective thunbergol formation under mild, solvent-free conditions, using molecular oxygen as a green oxidant.

Catalysts doi: 10.3390/catal16050423

Authors: Min Luo Wei Wu Linfei Xiao

Hydrogenation of CO2 to ethanol is regarded as a promising approach for the resource utilization of CO2. Ethanol can be synthesized via the acetate pathway over cobalt-based catalysts, in which the regulation of Co0-Coδ+ is crucial to increasing the space–time yield of ethanol. In this research, a series of Co-W-C catalysts was prepared via the reduction-carburization method and their catalytic performance was investigated for synthesizing ethanol from CO2 hydrogenation. During the preparation of Co-W-C catalysts, the Co, Co6W6C and WC phases were generated by employing a precursor containing Co, W and citric acid. This process drove the formation of Coδ+ species and the consequent generation of Co0-Coδ+ active pairs. Under the cooperation of Co0-Coδ+ and WC, ethanol was obtained with high selectivity and space–time yield from the CO2 hydrogenation under the promotion of DMF. Over the Co-W-C-1 catalyst prepared by a Co/W molar ratio of 1:1 in the precursor, an ethanol space–time yield of 17.1 mmol·g−1·h−1 with an ethanol selectivity of 99.6% among organic products was obtained. Furthermore, key intermediate species formed during the reaction were identified by in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy, and a possible reaction pathway was also proposed.

Catalysts doi: 10.3390/catal16050422

Authors: Hamed Namdar-Asl M. A. Mohtadi-Bonab Sadegh Pour-Ali Leila Fathyunes Farzaneh Shiran-Jang

In this study, TiO2 nanotube (TNTs) array electrodes were fabricated by electrochemical anodization and subsequently modified through thermal annealing, hydrogenation heat treatment, and chemical decoration with copper species at various immersion times to enhance their electrochemical performance. The structural, morphological, semiconducting, and electrochemical properties of the modified nanotubes were systematically examined. FE-SEM and EDS analyses confirmed the formation of well-aligned TNTs and the successful deposition of copper species, with the most uniform surface distribution achieved for the sample decorated for 45 min. Raman spectroscopy and XRD results revealed that the anatase phase of TiO2 remained stable after hydrogenation and copper decoration, while minor peak shifts indicated defect evolution and lattice distortion. Electrochemical evaluations, including linear sweep voltammetry, Tafel polarization, electrochemical impedance spectroscopy, and Mott–Schottky analysis, demonstrated a substantial enhancement in electrocatalytic activity following copper decoration. Compared with annealed and hydrogenated electrodes, the decorated samples exhibited markedly lower overpotentials, reduced cathodic Tafel slopes, and decreased charge-transfer resistance. Mott–Schottky analysis confirmed n-type semiconducting behavior for all electrodes, showing that hydrogenation increased donor density, whereas subsequent copper decoration slightly reduced it due to the partial substitution of oxygen vacancies by copper oxide species. Among all samples, the electrode decorated for 45 min (AA′HD45) exhibited the optimal balance between donor density, charge-transfer properties, and electrochemical performance. These results highlight the effectiveness of combining hydrogenation with optimized copper decoration to improve charge transport and interfacial kinetics in TNT electrodes for electrochemical applications.

Catalysts doi: 10.3390/catal16050420

Authors: Shijun Zhu Xinchen Zhang Shangming Shen Yang Wang Yongshu Hu Hao Yang Wenbin Liu Xiaoyan Ma Jing Deng

Biochar (BC)-activated peracetic acid (PAA)-based advanced oxidation processes (AOPs) were increasingly considered as cost-efficient and eco-friendly water treatment technologies for the removal of organic pollutants. However, the specific role of intrinsic carbon, nitrogen species and structure properties played in activation mechanism is still vague. In this study, the waste tea residues-based biochar (WTBC) was prepared by thermal carbonization and applied to activate PAA for the degradation of bisphenol A (BPA). The product carbonized at 800 °C (WTBC800) possessed larger specific surface area (342.57 m2/g), more abundant porous structure and massive defects state (ID/IG = 3.53), and exhibited a superior activation performance with 83.7% BPA removal within 120 min. Adsorption and non-radical oxidation pathways [e.g., the mediated electron transfer process (ETP) and singlet oxygen (1O2) generation] were evidenced to play the dominant roles in the BPA degradation through the formation of metastable complex WTBC-PAA*. The graphitic carbon, functional nitrogen species, defects structure and persistent free radicals (PFRs) in WTBC were proposed to contribute to the activation of PAA. Overall, relatively higher dosages of WTBC (0–0.5 g/L) and PAA (0–1.5 mM) facilitated the BPA degradation. The solution pH and water matrix (e.g., Cl−, NO3−, HCO3− and SO42−) presented a negligible effect on the BPA degradation in WTBC/PAA system. This study not only proposes a sustainable approach for organic pollutants removal in wastewater, but also promotes the resource re-utilization of agricultural waste.

Catalysts doi: 10.3390/catal16050421

Authors: Marco Zanon Theo Tonne Hønning Lyholm Yusuf Theibich Sara Jonsdottir Glaser Leila Lo Leggio

In this study, the native activity of an arabinogalactan endo-β-1,4-galactanase from Aspergillus niger (AnGal) was evaluated under different reaction conditions, and in the presence of various acceptor molecules during the cleavage of the β-1,4-glycosidic linkage of a chromogenic compound and lupin galactan. A combination of spectrophotometric assays, mass spectrometry and chromatography techniques provided insights into the reaction mechanism of the enzyme and its use in the synthesis of galactosides and galactooligosaccharide derivatives. In reactions containing 2-nitrophenol galactopyranoside, AnGal promoted transglycosylation, generating longer galactooligosaccharide derivatives of 2-nitrophenol that have not previously been reported for GH53 enzymes. Furthermore, new alcoholysis products have been detected when AnGal acted on lupin galactan in the presence of benzyl alcohol. To the best of our knowledge, we are first to report the synthesis of galactotriose and galactotetraose derivatives formed by endo-β-1,4-galactanase alcoholysis. This work showcases the potential of utilizing galactanases in the synthesis of valuable galactosides and galactooligosaccharides, under mild conditions from sustainable biomass sources. Potential beneficial applications may be found in several industrial fields such as in the preparation of prodrugs and prebiotics.

Catalysts doi: 10.3390/catal16050419

Authors: Mohamed Bechir Ben Hamida

This study focuses on simulating and optimizing cumene (isopropylbenzene) production via the alkylation of benzene with propylene using a beta zeolite catalyst. Two process configurations were evaluated: a conventional setup without a transalkylation reactor and an enhanced configuration incorporating a transalkylation unit to convert byproducts back into cumene. The process was modeled under steady-state conditions in Aspen HYSYS using plug flow reactors and the Peng–Robinson fluid package, with reaction kinetics derived from established literature on zeolite-catalyzed systems. Optimization studies examined the effects of reactor temperature, pressure, and the benzene-to-propylene molar ratio. Increasing the reactor temperature to 178 °C improved propylene conversion to 96.20%, while raising the pressure from 3540 kPa to 3600 kPa further enhanced it to 96.24%. By optimizing the benzene-to-propylene molar feed ratio to approximately 1.02:1 and increasing the fresh benzene feed to 138.5 kmol/h, cumene production reached 135.792 kmol/h while minimizing byproduct formation. Comparative analysis revealed that the configuration without a transalkylation reactor generated 4.171 kmol/h of diisopropylbenzene (DIPB) as waste, representing both economic loss and environmental concern due to its toxicity. In contrast, the integration of a transalkylation reactor enabled the conversion of DIPB into additional cumene, significantly improving process efficiency and sustainability. These findings demonstrate that optimizing reaction conditions and integrating a transalkylation step substantially enhances cumene yield and reduces waste, leading to a more viable and environmentally friendly industrial process.

Catalysts doi: 10.3390/catal16050418

Authors: Ai Qu Peiqing Yuan Xinru Xu Jingyi Yang

Acid Orange 3 (AO3) is a widely used azo dye in leather, paper, and textile dyeing. Untreated direct discharge into water bodies severely threatens human health and aquatic ecosystems, yet efficient degradation remains challenging for conventional technologies. In this work, RuO2/CeO2 heterostructure was synthesized and immobilized on a Ti substrate via controlled hydrothermal and annealing treatments, yielding RuO2/CeO2@Ti electrode. The electrode showed electrocatalytic activity for the oxygen evolution reaction (OER) over a wide pH range. Under optimized conditions (47 mA/cm2, pH 6, 0.25 M NaCl), 150 mg/L AO3 was degraded by 95.89% within 180 min. The degradation mechanism was elucidated by GC-MS and DFT (density functional theory) calculations. The degradation process was dominated by indirect oxidation, sequentially involving azo bond cleavage, heterocyclic ring opening, desulfurization, denitrification, benzene ring cleavage, and mineralization of small molecules into H2O and CO2.

Catalysts doi: 10.3390/catal16050417

Authors: Ziyan Mi Huayun Long Yuhua Jia Yue Ma Cuilan Miao Yan Xie Xiaomei Zhu Jiahui Huang

Developing effective catalysts for the epoxidation of propylene with H2 and O2 holds significant scientific and industrial significance. This study synthesized a series of Au/TS-1 catalysts modified with alkali metals (Na+, Cs+) and carefully examined their impact on gas-phase propylene epoxidation, with particular attention to the role of anions. The optimal Au–CsC(1:10)/TS-1 catalyst (Cs2CO3 modified, Au/Cs molar ratio = 1:10) achieves a propylene conversion of 16.8%, a PO selectivity of 88.5%, an H2 efficiency of 40.8%, a record PO formation rate of 383.9 gpo·kgcat−1·h−1, and unprecedented long term stability (>380 h without deactivation). To the best of our knowledge, no previous study has simultaneously achieved such balanced and outstanding performance across all these key indicators. Comprehensive characterization reveals that Cs+ modification suppresses side reactions and coke formation, increases microporosity, tunes surface acid–base properties and hydrophobicity, restricts Au particle size, and stabilizes both Au0 and tetra coordinated Ti sites, thereby inhibiting H2O2 decomposition and PO isomerization while greatly enhancing reaction efficiency. This holistic advancement represents a significant leap forward for Au based catalysts in gas phase propylene epoxidation, offering both a theoretical foundation and practical guidance for the development of high performance epoxidation catalysts.

Catalysts doi: 10.3390/catal16050412

Authors: Harry Lik Hock Lau Nur Amirah S. Yussof Nur Diana Bazilah Awang Idris Rusydi R. Sofian Syahirah Nabilah Aedy Aewandy Nur Aisyah Abdul Munir Nur Nabaahah Roslan Eny Kusrini Muhammad Nur Anwar Usman

Titanium-based perovskites have garnered significant attention for photocatalytic applications, particularly in the field of environmental remediation through the degradation of synthetic dyes and pharmaceuticals in aqueous solutions. This review paper aims to explore the synthesis methods, crystal structures, photoactivity, and photocatalytic performance of titanium-based perovskites in degrading synthetic dye and pharmaceutical effluents in water. The unique advantages of titanium-based perovskites as photocatalysts, associated with their high redox potentials and excellent optical and electrical properties, are highlighted. Their limitations in visible light absorption and photocatalytic efficiency due to rapid charge carrier recombination are also discussed. Several strategies to overcome these limitations, such as surface modifications of the photocatalysts, metal and non-metal doping, the introduction of structure defects, the formation of heterojunctions with electron-accepting materials, and the deposition of plasmonic metal nanoparticles are systematically examined. This review also provides an overview of the photocatalytic degradation of dyes and pharmaceuticals as emerging contaminants, utilizing titanium-based perovskites as photocatalysts, to highlight their efficiency and potential for real-word applications. By covering research findings, current knowledge, and future perspectives, this review aims to stimulate advancements in the design and application of titanium-based perovskite photocatalysts.

Catalysts doi: 10.3390/catal16050413

Authors: Maria B. Moura Elisabete P. Carreiro Pedro Paiva Hans-Jürgen Federsel Anthony J. Burke

Over the last 20 years, Deep-Eutectic Solvents (DES) have been making a significant impact in the field of chemistry, with applications in nanotechnology, biomass transformation, electrochemistry pharmaceuticals and a host of other applications that includes catalysis. Considering the importance of chiral organocatalysis for the selective synthesis of drugs, pharmaceuticals and fragrances, etc. DESs were quickly harnessed as the media for carrying out organocatalytic transformations. In this review, we discuss some of the most important examples from the literature that have made an impact in the field over the last 5 years. A more recent development has been the incorporation of DESs in structured and self-organized gel-like assemblies that are known as EutectoGels. These soft structures offer a more defined and compact environment that can influence stereoselectivity by pre-organizing the reactants in three-dimensional space, and potential control the types of transition states that can be formed.

Catalysts doi: 10.3390/catal16050416

Authors: Ermete Antolini

Among different non-carbon materials, due to their high corrosion resistance and chemical stability, titanium-based compounds, such as TiO2, TiN, TiC and Ti3C2Tx, are potential supports for PEMFC catalysts. In addition to its main function as a support, due to its catalytic properties, TiO2 is also used as co-catalyst/additive in the catalyst layer. In this work, the use of titanium compounds as catalyst supports and co-catalysts in the membrane electrode assembly of PEMFCs is overviewed and discussed.

Catalysts doi: 10.3390/catal16050415

Authors: Fei Chang Xinyi Cai Jing Xu Fuyu Hong Hongyu Yang Deng-Guo Liu

Formaldehyde (HCHO) is a typical volatile organic compound (VOC) that poses significant risks to human health. Long-term exposure, even at low concentrations, has been associated with various malignant diseases, including nasopharyngeal, colon, and brain cancers. Common technologies for HCHO abatement include ventilation, adsorption, photocatalysis, and catalytic oxidation. Among these methods, catalytic oxidation is regarded as the most promising due to its high removal efficiency, low cost, minimal energy consumption, and no toxic by-products. In recent years, supported catalysts with excellent room-temperature activity and high dispersibility have attracted considerable attention. These catalysts can usually be divided into two categories: noble metal catalysts and non-noble metal catalysts. Zirconia (ZrO2) has become an ideal support owing to its advantages of high specific surface area, abundant and tunable acid–base sites, and strong metal–support interaction (SMSI). Various modification strategies have been developed to improve the catalytic performance of ZrO2-based systems, such as the construction of phase interfaces and the stabilization of single-atom species. This review summarizes the recent research progress of ZrO2-based systems for the catalytic oxidation of formaldehyde. It provides a detailed discussion of the physicochemical properties of ZrO2 supports and the reaction mechanisms involved, and highlights achievements in crystal phase regulation, elemental doping, metal–support interaction, and composite modification. Finally, future challenges and development directions for these catalysts are also outlined.

Catalysts doi: 10.3390/catal16050414

Authors: Alyson R. Ribeiro Jose A. Casas Juan A. Zazo Jefferson E. Silveira

This study investigates a combined advanced oxidation process (AOP) utilizing UVA-LED irradiation (365 nm) for the degradation of sucralose (SUC), a complex artificial sweetener that poses a challenge for wastewater treatment due to its resistance to conventional methods. A sequential treatment strategy was employed. The initial step utilized UVA-activated persulfate (PS) at varying dosages (0.12–0.5 g/L) and UVA fluence rate (ranging from 20 to 100% of nominal output). The influence of natural water components (bicarbonate, chloride, sulfate, and nitrate) on PS activation was systematically analyzed. Notably, the substantial pH decrease during oxidation opened the possibility of replacing an amount of PS with the less expensive and more environmentally friendly hydrogen peroxide (H2O2) in the subsequent Fenton reaction. This second step employed a stoichiometric dosage of H2O2 (2.12 g/g COD) and varying Fe2+ concentrations (0.05–0.2 g/L), achieving a 95% overall mineralization within 60 min. The combined process incurred an approximate cost of 2.5€ per m3. This research contributes to the development of more effective and environmentally friendly wastewater treatment strategies for emerging contaminants.

Catalysts doi: 10.3390/catal16050411

Authors: Xiaofei Sun Dongwang Zhang Rushan Bie Man Zhang

Biomass gasification technology is a crucial pathway for obtaining clean syngas and achieving efficient utilization of carbon resources. However, tar is one of the main factors restricting the industrialization of biomass gasification technology. Among various solutions, catalytic steam reforming is regarded as the most promising solution. Currently, natural minerals and Ni-based catalysts have been demonstrated to be effective and economically viable for tar removal, which are widely used in industrial fluidized beds. Therefore, the basic reaction principles of tar steam reforming were briefly introduced. The development of tar steam reforming catalysts, focusing mainly on natural minerals and Ni-based catalysts, have been studied in this review. The catalytic cracking mechanisms of natural minerals such as dolomite and limestone, as well as the steam reforming mechanism of Ni-based catalysts, have been thoroughly summarized. In addition, the active sites of the catalysts, reaction pathways, and the essence of catalyst deactivation are discussed. Based on this, the catalytic effect of these two catalysts for steam reforming of tar in the fluidized bed was summarized. Further, the engineering challenges (such as mass transfer, wear, and continuous regeneration) and the corresponding process optimization measures were comprehensively reviewed, and future perspectives are discussed.

Catalysts doi: 10.3390/catal16050410

Authors: Karoline K. Ferreira Lucília S. Ribeiro Manuel Fernando R. Pereira

Co and Mo mono- and bimetallic catalysts supported on CNT-H-ZSM-5 composites were prepared and characterized using various techniques. The catalysts were evaluated for the conversion of sunflower oil (SO) into sustainable aviation fuel (SAF) hydrocarbons in the C8–C16 range. The effects of reduction temperature and metal loading were the main parameters investigated in this study. The catalyst reduced at 600 °C promoted the formation of Mo2C species, resulting in high SO conversion (84%), complete deoxygenation, and enhanced isomerization within the C8–C16 fraction. Optimal metal loadings (2.5 wt% Co and 8 wt% Mo) and the bimetallic configuration led to superior performance compared with monometallic catalysts and physical mixtures, clearly highlighting a synergistic effect between Co and Mo species. In contrast, when waste cooking oil was used as feedstock, lower conversion and reduced selectivity toward SAF-range hydrocarbons were observed, which were attributed to the higher complexity and impurity content of this residue feedstock.

Catalysts doi: 10.3390/catal16050409

Authors: Linhao Zhang Hong Liu Jianming Zhang Fagen Wang

Harnessing low-grade thermal energy from industrial processes and the environment represents an attractive route toward sustainable chemical production. In this work, we report a thermoelectrocatalytic (TE-Catal) system capable of converting small temperature gradients into chemical energy for hydrogen peroxide (H2O2) generation. A hybrid catalyst composed of nickel-based metal–organic frameworks (Ni-MOFs) nanoparticles integrated with carbon nanotubes (CNTs), Ni-MOFs/CNTs, was synthesized through a facile one-pot strategy. Under a temperature gradient, the thermoelectric response of the Ni-MOFs induces charge carrier generation through the Seebeck effect, enabling interfacial redox reactions that produce H2O2. However, rapid recombination of thermally generated carriers typically limits catalytic efficiency. By coupling Ni-MOFs with conductive CNTs networks, charge separation and transport are significantly enhanced due to the strong interfacial interaction and the high electrical conductivity of CNTs. As a result, the Ni-MOFs/CNTs nanohybrids exhibit greatly improved H2O2 generation rate of ~111.7 µmol g−1 h−1 compared with pristine Ni-MOFs (31.8 µmol g−1 h−1). Thermoelectric electrochemical measurements confirm that the CNT incorporation effectively promotes carrier migration and suppresses recombination. This study demonstrates the potential of MOF-based thermoelectric nanostructures for transforming waste heat into valuable chemical products.

Catalysts doi: 10.3390/catal16050408

Authors: Iskra Z. Koleva Ivana Hristova Boyana Sabcheva Polya V. Koleva Francesc Viñes Hristiyan A. Aleksandrov

Sulfur is a well-known catalyst poison, particularly for catalysts based on transition metals. Herein, we studied the adsorption of sulfur species on small nanoparticles (~1 nm in size) of the face centered cubic (fcc) transition metals (Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au) using density functional theory (DFT) modeling. At low sulfur coverage (one S atom per nanoparticle), sulfur preferentially occupies the surface hollow sites of the nanoparticles. At higher coverage, however, the subsurface diffusion of S in Ni, Pd, and Ag nanoparticles becomes energetically favorable with low activation energies. Among the considered metals, sulfur binds most strongly to Rh and Ir, and most weakly to Ag and Au. The present results shed light on the facility of S-poisoning on such metal nanoparticles, either by surface blocking or by underlying sulfurization of the metal.

Catalysts doi: 10.3390/catal16050407

Authors: Luciana Lisi Elisabetta Maria Cepollaro Michele Emanuele Fortunato Stefano Cimino

This study investigates the synergistic promotional effects of CeO2 and La2O2SO4 as composite catalytic oxygen storage systems for soot oxidation in Gasoline Particulate Filters (GPFs) across a broad operating temperature range. Two 5 wt % CeO2-promoted Lanthanum oxysulfate compounds were prepared by mechanical mixing of pure phases or by supporting CeO2 via incipient wetness impregnation with a cerium nitrate precursor. The soot oxidation activity was evaluated using Thermogravimetric Analysis coupled with Mass Spectrometry (TG-MS) under both anaerobic and lean-O2 (1% vol.) environments, with the performance benchmarked against pure La- or Pr-oxysulfates and CeO2 reference materials. Comprehensive characterization via XRD, SEM, N2-physisorption, and H2-TPR revealed that the observed synergistic effects transcend the simple additive properties of the individual components.

Catalysts doi: 10.3390/catal16050406

Authors: Amira Saidani Mouna Saidani Reguia Boudraa Ikram Boucekine Karim Fendi Abderrahim Benabbas Atmane Djermoune Abdelhafid Souici Hamdi Bendif Mohamed A. M. Ali Gharieb S. El-Sayyad Lotfi Mouni

ZnO–ZnCr2O4 heterojunction nanocomposites were synthesized via co-precipitation with nominal spinel loadings of 10, 20, and 30 wt.% (denoted ZnCr-10, ZnCr-20, ZnCr-30) to evaluate structure–property–performance relationships in photocatalytic dye degradation. Rietveld refinement of XRD data revealed actual crystalline phase fractions of 12.1%, 32.4%, and 39.9% ZnCr2O4, respectively, with systematic morphological evolution from dispersed nanoparticles (ZnCr-10) to densely agglomerated structures (ZnCr-30) observed by SEM. Optical analysis demonstrated that ZnCr-10 (apparent band gap 3.09 eV) retains ZnO-dominated absorption with moderate interfacial electronic coupling, while ZnCr-20 shows enhanced visible response (2.89 eV) through interface-mediated transitions. ZnCr-30 exhibits strong sub-bandgap absorption (1.63 eV) originating from defect states rather than intrinsic band narrowing. Photoluminescence studies under UV excitation revealed optimal radiative recombination suppression in ZnCr-10, consistent with efficient interfacial charge separation, whereas excessive loading (ZnCr-30) introduced defect-mediated recombination centers. Photocatalytic degradation of Rhodamine B (5 mg/L, 0.5 g/L catalyst, solar irradiation) followed the order: ZnCr-10 (k = 0.0307 min−1) > ZnO (0.0203 min−1) > ZnCr-20 (0.0230 min−1) > ZnCr2O4 (0.0166 min−1) > ZnCr-30 (0.0113 min−1). The optimal ZnCr-10 performance is attributed to balanced interfacial contact between phases enabling charge separation without excessive agglomeration or defect accumulation. Operational parameters (pH 7, 50 mg/100 mL, 100 µL H2O2) were optimized, achieving 98% degradation in 60 min. This study demonstrates that photocatalytic enhancement in ZnO–spinel heterojunctions is governed by interfacial architecture and defect management rather than optical absorption alone, providing design principles for efficient solar-driven environmental remediation.

Catalysts doi: 10.3390/catal16050405

Authors: Mihaela Litinschi (Bilegan) Rami Doukeh Romuald Győrgy Ionuț Banu Alexandru Vlaicu Gabriel Vasilievici Sorin Georgian Moga Andreea Madalina Pandele Dragos Mihael Ciuparu

Ammonia decomposition represents a promising route for CO2-free hydrogen production; however, the development of efficient and stable catalysts remains a critical challenge. In this work, a series of Al-based mixed-oxide catalysts (AlM, where M = Ni, Co, Ce) were synthesized via co-precipitation and systematically investigated to elucidate the relationship between physicochemical properties and catalytic performance in ammonia decomposition. Comprehensive characterization by X-ray diffraction (XRD), N2 physisorption (BET), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and pyridine-adsorbed Fourier transform infrared spectroscopy (FTIR-Py) revealed significant variations in surface area, morphology, dispersion, and acidity as a function of the incorporated metal. Among the investigated catalysts, the AlNi system exhibited superior activity, achieving the highest ammonia conversion over the studied temperature range. This enhanced performance is attributed to its high specific surface area, homogeneous mesoporous structure, and a balanced distribution of Lewis/Brønsted acid sites, which promote effective ammonia adsorption, activation and decomposition. Kinetic analysis further confirmed the favorable reaction pathway on AlNi, as evidenced by its lower apparent activation energy and higher pre-exponential factor compared to the other materials. The results demonstrate a clear correlation between surface acidity, textural properties, and catalytic performance, highlighting the pivotal role of AlM interactions in governing ammonia decomposition. These findings provide valuable insights for the rational design of efficient catalysts for hydrogen production from ammonia.

Catalysts doi: 10.3390/catal16050404

Authors: János Kiss Imre Szenti Anastasiia Efremova Imre Kovács Aranka Deér András Sápi Zoltán Kónya

The performance and mechanism of heterogeneous catalytic reactions are fundamentally governed by the formation, stability, and reactivity of transient surface intermediates. These species—such as isocyanates, alkyl groups, carboxylates, formates, carbonates, alkoxy and acyl intermediates—often exist at low concentrations and with short lifetimes, making their identification challenging. This review summarizes the current knowledge on the formation, spectroscopic identification, and thermal behavior of these intermediates on metal single crystals, metal nanoparticles, and oxide-supported catalysts. Emphasis is placed on key reactions including CO and NO oxidation–reduction, CO and CO2 hydrogenation, Fischer–Tropsch-related pathways, and reforming of ethanol. Advanced surface-sensitive techniques (TDS, XPS, UPS, IR, HREELS) are highlighted for their role in elucidating intermediate structures and reaction pathways. The isocyanate surface complex is an existing intermediate in NO reduction with CO, and NCO is responsible for NH3 formation. Alkyl groups can be prepared from thermal- or photo-induced dissociation of alkyl halogenide. Oxygen-containing intermediates relevant to CO2 hydrogenation are addressed, with particular attention to formate, carboxylate, and related species. M/CeO2 (M = Pt, Rh, Ir, Ru) seems to be the best catalyst for hydrogen production from ethanol reforming. The nature of support may affect hydrogen production. The review also discusses how metal–support interactions, particle size, and surface morphology influence intermediate stability and catalytic selectivity. Overall, the work provides a comprehensive framework for understanding how transient surface complexes control technologically important catalytic transformations.

Catalysts doi: 10.3390/catal16050403

Authors: Yan He Ziyi Li Ebtihal Abograin Yuntian Wan Yan Yan Xu Yan Yongsheng Yan Wei Peng

The efficient photocatalytic generation of hydrogen peroxide (H2O2) from pure water remains a formidable challenge, primarily due to the rapid recombination of photogenerated electron–hole pairs and insufficient redox potentials inherent in single-component photocatalysts. To address these issues, we designed and synthesized a heterojunction material comprising cadmium sulfide nanoparticles loaded on carbon spheres (CS@CdS). Under conditions utilizing pure water and ambient air, the CS@CdS composite achieves an H2O2 production rate of 1305 μmol·g−1·h−1, which is 3.1 and 3.6 times higher than that of pure CdS and CS, respectively, without the need for any sacrificial agents or external oxygen supply. Systematic characterization reveals that CS and CdS form a tightly coupled electronic interface, which significantly accelerates charge carrier separation and effectively prolongs the lifetime of photogenerated carriers, thereby boosting photocatalytic performance. Furthermore, the CS component extends the visible-light absorption range of the composite and functions as an electron acceptor to suppress charge recombination, collectively endowing CS@CdS with enhanced photocatalytic activity. Mechanistic studies indicate that H2O2 production over CS@CdS proceeds predominantly via a two-step single-electron oxygen reduction reaction (ORR) pathway. This work offers a viable strategy for constructing CS-based heterojunction photocatalysts for efficient H2O2 synthesis.

Catalysts doi: 10.3390/catal16050402

Authors: Lewa Zhang Joseph Cao Bowen Liu Rongze Li Bangwei Deng Chenyuan Zhu

Electrocatalytic nitrate reduction to ammonia (NH3) offers a sustainable alternative to the Haber–Bosch process while enabling remediation of nitrate-contaminated water. However, the mechanistic origin of performance differences among bimetallic catalysts remains poorly understood, particularly regarding the metal-dependent evolution of reaction intermediates. Here, we construct a series of phase-pure tandem Cu–M catalysts (M = Co, Ni, Fe, Sn) by physically integrating commercial nanoparticles to examine the role of the secondary metal. In this architecture, Cu governs nitrate adsorption and its initial reduction to nitrite, whereas M dictates downstream hydrogenation toward NH3. Operando ATR–FTIR spectroscopy reveals that NH3 FE is determined by the hydrogenation kinetics of nitrite-derived intermediates rather than nitrate activation itself. Among the examined systems, Cu–Co achieves optimal kinetic matching, enabling rapid nitrite consumption and continuous hydrogenation, delivering an ammonia Faradaic efficiency of 91.2% with minimal nitrite accumulation (~1.0%) and a yield rate of 0.86 mmol h−1 cm−2 at −0.5 V vs. RHE. In contrast, Ni and Fe exhibit sluggish hydrogenation, while Sn induces pronounced intermediate buildup. These findings identify nitrite hydrogenation as the selectivity-determining step in tandem nitrate reduction and establish the chemical nature of the secondary metal as a decisive descriptor for rational catalyst design.

Catalysts doi: 10.3390/catal16050401

Authors: Boyu Chen Yuanzhe Li Liantao Yang Biao Zhang Hao Wang

To address the critical challenges of sluggish C-C coupling kinetics and the propensity for over hydrogenation to ethane (C2H6) in the photocatalytic CO2 reduction to ethylene (C2H4), this study designed a synergistic bimetallic Pt/Co cluster catalyst supported on a covalent organic framework (COF), designated as PtCo-TpBD COF. This catalyst is designed to modulate the adsorption of key intermediates via Co clusters to suppress over-hydrogenation, while leveraging Pt clusters to promote C-C coupling, thereby achieving highly selective C2H4 production. Through a series of structural characterization analyses, it was confirmed that Pt/Co clusters were successfully confined within the pores of the COF, and significant electronic interactions were observed. In situ infrared spectroscopy revealed that the introduction of Co clusters effectively weakens the adsorption strength of the CO* intermediate, while the incorporation of Pt clusters promotes C-C coupling. In visible-light-driven gas-phase CO2 reduction, this catalyst delivered exceptional activity, reaching an C2H4 formation rate of 7.54 μmol g−1 h−1 and an C2H4 selectivity of 90.1%, along with remarkable inhibition of deep hydrogenation byproducts including C2H6. This study not only provides a successful example for constructing efficient bifunctional photocatalysts to achieve highly selective conversion of CO2 to C2H4, but also highlights the great potential of COFs as advanced platforms for integrating multifunctional metal clusters and precisely tuning catalytic selectivity.

Catalysts doi: 10.3390/catal16050400

Authors: Longxin Zhao Xinyan Jiang Jiayi Wang Junqi Rong Shiyuan Sun Yongzhuo Liu

Reverse chemical looping pyrolysis (RCLPy) utilizes a reduced oxygen carrier to extract oxygen from the biomass feedstock during the pyrolysis stage and transfer it for the subsequent gasification stage. This decoupled mechanism enables efficient in situ utilization of oxygen and hydrogen inherent in the biomass to produce a hydrogen-rich syngas. In this work, Ca–Fe–Ni composite oxygen carriers for RCLPy were synthesized and their impact on the hydrogen production was investigated and optimized. The results demonstrate that the reduced Ca–Fe–Ni oxygen carrier exhibited both excellent deoxygenation and catalytic cracking capability, significantly promoting the generation of hydrogen and CO. Specifically, the reduced CaFeNi15 oxygen carrier decreases the CO2 content in the pyrolysis gas from 40.4 vol.% without an oxygen carrier to 6.89 vol.% and with a hydrogen yield of 280.2 mL⸱g−1 biomass and has a total hydrogen production of 318 mL⸱g−1 biomass during the whole pyrolysis–gasification process. These findings underscore the advantages of the RCLPy process in utilizing inherent biomass hydrogen for high-purity syngas production. Future efforts should focus on developing oxygen carriers with enhanced long-term cyclic stability.

Catalysts doi: 10.3390/catal16050399

Authors: Rehab Mahmoud Seham M. Hamed Abdullah S. Alawam Ahmed A. Allam Amany Abd El-Halim Engy Hany Gabrail Ghabraiel Hala Mohamed Alaa A. Ahmed-Anwar Sarah O. Makled Samar M. Mahgoub

A sustainable strategy was developed to valorize rabbit manure waste by synthesizing a porous quaternary Ni-Co-Zn-Fe layered double hydroxide/biochar nanocomposite (QL-RMB) for the efficient removal of Mn(VII) in the form of permanganate (MnO4−) from aqueous solutions. The QL-RMB adsorbent exhibited a well-developed mesoporous structure with uniformly dispersed nanoparticles, achieving 73% MnO4− removal within 60 min under optimized conditions (pH 3.0; dosage 0.5 g L−1). Adsorption followed pseudo-second-order kinetics and was best described by the Freundlich isotherm model (R2 > 0.98), yielding a maximum Langmuir adsorption capacity (qmax) of 45.13 mg g−1. Statistical physics modeling confirmed a multi-ionic, vertically oriented adsorption configuration, while thermodynamic analysis demonstrated that the process was spontaneous and exothermic, governed by electrostatic attraction, anion exchange, and surface complexation. The QL-RMB composite exhibited excellent MnO4− selectivity in the presence of competing ions (selectivity coefficients: 24.96 for Fe3+, 31.59 for Ni2+, 23.56 for Zn2+) and retained significant removal efficiency (73.96%) after five regeneration cycles. In a circular economy approach, the Mn (VII)-spent adsorbent (QL-RMB/Mn) was valorized as an electrocatalyst for urea electro-oxidation, achieving a current density of ~127.19 mA cm−2 for pristine QL-RMB, which increased to ~217.07 mA cm−2 after Mn(VII) adsorption (QL-RMB/Mn) in 1 M KOH/1 M urea. Batch scale-up studies revealed an efficiency of 42.55 g or 95% MnO4− removal from 50 L water, with a low estimated production cost of 0.0602 USD g−1. Environmental sustainability was confirmed by the National Environmental Methods Index (NEMI), modified Green Analytical Procedure Index (Mo-GAPI), Eco-scale (score: 77), and Analytical GREEness (AGREE) assessment frameworks.

Catalysts doi: 10.3390/catal16050398

Authors: Paula Garín Humberto Brito Isabel Cáceres Carola Bahamondes

This work presents a novel integrative approach to the design and computational modeling of a bioreactor system for the enzymatic removal of antibiotics from aquatic environments. The study focuses on a three-dimensional mathematical model developed to resolve the diffusion–convection–reaction dynamics within the system. Programmed in MATLAB R2025a, the model integrates theoretical equations to determine the diffusion and convection coefficients, while the reaction rate constant was precisely determined through the experimental degradation data of oxytetracycline. To support this modeling, laccase was covalently immobilized on a chemically modified polylactic acid (PLA) matrix, achieving a 95.6% immobilization yield. Simulation results revealed that the system is primarily governed by the convection constant and that degradation efficiency is significantly optimized by reducing the reactor’s internal diameter. These findings demonstrate that the coupling of theoretical transport phenomena with experimentally derived kinetics provides a high-resolution tool for predicting bioreactor performance. By combining biocatalysis, materials science, and computational modeling, this research offers a scalable and environmentally friendly solution with direct implications for the development of advanced water treatment technologies.

Catalysts doi: 10.3390/catal16050397

Authors: Henan Shang Qi Jia Shilei Zhang Sijia Li Jinsheng Liang

A novel citric acid-assisted in situ reduction method has been developed for the synthesis of bimetallic AuPd alloy nanoparticles supported on amine–phosphate-functionalized carbon nanotubes (AuPd/NH2-P-CNTs). In this strategy, formic acid acts not only as the reducing agent for reducing metal precursors, but also as the hydrogen source for the subsequent catalytic dehydrogenation. The introduction of citric acid significantly accelerates the reduction kinetics and promotes the uniform formation of ultrafine AuPd nanoparticles (∼1.8 nm). As a result, the optimized Au0.5Pd0.5/NH2-P-CNTs exhibit an extraordinary catalytic activity and 100% H2 selectivity during hydrogen generation from FA with sodium formate as an additive, affording a remarkable initial turnover frequency of 5663.94 mol H2 mol Pd−1 h−1 at 303 K. The experimental results reveal that the -NH2 and -P functional groups on the support are crucial for stabilizing and uniformly dispersing the alloy nanoparticles. Furthermore, the enhanced reaction rate can be attributed to the strong metal–support interaction established between AuPd nanoparticles and -NH2-P-CNT supports. This work provides a new perspective on the design of highly efficient Pd-based catalysts for hydrogen production from formic acid.

Catalysts doi: 10.3390/catal16050396

Authors: Liyang Peng Qinjun Chen Pengcheng Su Jinhui Zhang Shibiao Wu

Graphitic carbon nitride (CN) is a promising photocatalytic material, but its practical application is limited by small specific surface area, narrow light absorption range, and high photogenerated carrier recombination rate. To address these issues, this study synthesized boron-doped carbon nitride (BCN) and sulfuric acid-exfoliated boron-doped carbon nitride (BCND). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirmed that boron was successfully doped into the CN skeleton via B-N bonds. Scanning electron microscopy (SEM) and N2 adsorption–desorption (BET) characterizations showed that acid exfoliation significantly increased the specific surface area of BCND to 68.80 m2·g−1, much higher than that of CN (9.54 m2·g−1) and BCN (15.98 m2·g−1). UV–visible diffuse reflectance spectroscopy (UV-Vis DRS) analysis revealed that BCND had the narrowest bandgap (2.59 eV) among the three materials, which enhanced its visible-light absorption efficiency. Photoelectrochemical tests demonstrated that BCND exhibited the smallest charge transfer resistance and the highest transient photocurrent density (eight times that of CN), indicating efficient separation of photogenerated electron–hole pairs. Photocatalytic water splitting experiments showed that BCND achieved the highest Hydrogen production rate of 792.34 μmol·g−1·h−1, which was about 4 times that of CN (158.41 μmol·g−1·h−1) and 1.36 times that of 2.5% BCN (584.30 μmol·g−1·h−1). Free-radical trapping experiments indicated that hydroxyl radicals (·OH) played a crucial promotional role in Hydrogen production, while superoxide anions (·O2−) exerted an inhibitory effect. The enhanced performance of BCND was attributed to the synergistic effects of boron doping (narrowing bandgap) and acid exfoliation (increasing specific surface area). A possible photocatalytic Hydrogen production mechanism was proposed based on the experimental results. This study provides a feasible strategy for the structural modification and performance optimization of g-C3N4-based photocatalysts for water splitting.

Catalysts doi: 10.3390/catal16050395

Authors: Yunze Jin Xiangrui Liu Guojian Jiang

To improve the visible-light-driven photocatalytic degradation efficiency of g-C3N4-based photocatalysts toward organic pollutants, a MoS2/g-C3N4 composite precursor was employed in this work, and the phase composition and defect environment of Mo species were regulated by post-annealing under air and N2 atmospheres, respectively, thereby constructing Mo-based/g-C3N4 (MCN) composites with distinct structural evolution characteristics. The results showed that the photocatalytic activity of the as-sonicated MCN composite toward methylene blue (MB) was only moderately improved, among which the 15% loading sample exhibited the best performance with a degradation efficiency of about 42.0% within 60 min. In contrast, annealing at 400 °C under N2 resulted in only a slight activity change, whereas the sample treated at 400 °C in air (Air-15% MCN) achieved an MB degradation efficiency of 99.9% within 60 min, together with a much higher pseudo-first-order reaction rate constant than that of the air-treated sample at a lower temperature. XRD, FT-IR and XPS analyses revealed that air annealing induced the conversion of MoS2 into highly crystalline MoO3 (or MoO3₋x), leading to the formation of a reconstructed MoO3₋x/g-C3N4 composite interface. Meanwhile, the increased high-binding-energy component in the O 1s spectrum and the EPR signal around g ≈ 2.00 further suggested the presence of more abundant defect-related centers in the air-treated sample. Although Air-15% MCN possessed a lower specific surface area than the untreated and N2-treated samples, it displayed enhanced visible-light absorption, higher transient photocurrent response, lower interfacial charge-transfer resistance, and accelerated carrier dynamics, indicating that the activity enhancement mainly originated from atmosphere-induced phase transformation, interfacial reconstruction, defect-related active centers, and improved charge separation/transfer, rather than from the surface area effect. Based on the above results, a possible interfacial charge-transfer pathway is tentatively proposed for the g-C3N4/MoO3₋x interface formed after air treatment, which contributes to the efficient utilization of photogenerated carriers and the rapid degradation of MB. This work demonstrates that atmosphere-induced phase transformation is a simple and effective strategy for regulating the structure and photocatalytic performance of Mo-based/g-C3N4 composites, and provides useful guidance for the design of efficient visible-light photocatalysts.

Catalysts doi: 10.3390/catal16050394

Authors: José Guadalupe Rivera Juan Manuel Olivares-Ramírez Raúl García-García German Orozco

The electrochemical behavior of metallic rhenium was investigated using voltammetry and ex situ X-ray photoelectron spectroscopy (XPS) in aqueous acidic methanol solutions. Capacitance–potential analysis revealed that the double-layer current is governed by an adsorption–desorption surface process involving oxygen and sulfate species, as confirmed by XPS. The hydrogen evolution reaction (HER) proceeds via a Volmer–Heyrovsky mechanism, with hydrogen adatoms, physisorbed oxygen, and chemisorbed sulfate molecules as key intermediates. Methanol does not inhibit hydrogen gas production, and oxygenated species actively participate in the HER pathway. Voltammetric measurements demonstrated that rhenium cathodes are highly efficient for methanol electrolysis in membraneless systems, suggesting their potential application in electrolysis processes involving unpurified wastewater. These findings highlight rhenium as a promising electrode material for use in sustainable energy conversion technologies.

Catalysts doi: 10.3390/catal16050392

Authors: Mohammad Arishi Mohammed Kuku Abdullah M Maghfuri Ahmed Abutaleb Ayman Yousef M. M. El-Halwany

Efficient, low-cost catalysts are required for on-demand H2 generation from chemical hydrides. This study utilized piezoelectric poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers (NFs) as a support to encapsulate bimetallic Co–Mo nanoparticles (NPs) for H2 production via sodium borohydride (SBH) methanolysis. The PVDF-HFP membranes were synthesized through electrospinning, followed by in situ SBH reduction, which resulted in the uniform dispersion of amorphous Co–Mo NPs within the nanofibrous matrix. The optimized CoMo-0.2@PVDF-HFP membrane exhibited a hydrogen generation rate (HGR) of 1.9 × 103 mL·min−1·g−1 (Co) at 298 K, indicating a 3.6-fold improvement relative to monometallic Co. Kinetic studies showed a nearly first-order relationship with catalyst dose and a nearly zero-order relationship with respect to SBH concentration, suggesting kinetics controlled by surface saturation. The activation energy (Ea) was determined to be 14.03 kJ·mol−1. Moreover, the catalyst maintained over 80% of its original activity after five cycles. This enhanced performance is attributed to the combined effects of Co and Mo, the amorphous nature of the active sites, and the piezoelectric polarization of PVDF-HFP during mechanical stirring, which together improve charge transfer and reduce NP agglomeration.

Catalysts doi: 10.3390/catal16050393

Authors: Shengzhuang He Airan Guo Haijuan Yu Tielong Li Qingyu Li Zongming Xiu

Trichloroethylene (TCE) is a pervasive groundwater contaminant, yet the practical application of nanoscale zero-valent iron (nZVI) is often limited by particle aggregation, rapid surface oxidation, and inefficient utilization of reactive electrons. Here, we developed a support–sulfidation coupled design to improve TCE dechlorination by integrating ZIF-8-enabled contaminant enrichment and dispersion with sulfidation-enabled surface-state regulation. A ZIF-8-supported sulfidated nZVI composite (ZIF-8@S-nZVI) was synthesized and systematically compared with nZVI, S-nZVI, and ZIF-8@nZVI. Among the tested materials, ZIF-8@S-nZVI exhibited the fastest TCE removal, the highest ethylene formation, and the highest chloride release, indicating the most effective dechlorination performance rather than merely adsorption-driven apparent removal. The optimal Fe:ZIF-8 mass ratio was 6:1. The composite also maintained high dechlorination capability over 20–40 °C, pH 6–9, and initial TCE concentrations of 10–40 mg/L, although 20 °C, near-neutral pH, and lower pollutant loading were kinetically more favorable. Multiscale characterization by FT-IR, N2 adsorption–desorption and BET, XRD, EDS, SEM, and XPS indicated that ZIF-8 mitigated particle aggregation and retained partial pore accessibility, whereas sulfidation was associated with a more persistent Fe(II)-rich surface state after reaction. Together, these coupled effects promoted local TCE enrichment and sustained interfacial transformation. This study provides mechanistic insight and practical guidance for the rational design of MOF-supported sulfidated iron materials for chlorinated-solvent-contaminated groundwater remediation.

Catalysts doi: 10.3390/catal16050391

Authors: Lixin Sun Qitu Zhang

Developing high activity calcium-based adsorbent is still one of the difficult problems for calcium-based adsorbents for dry desulfurization. Herein, we develop the surfactant induction coprecipitation strategy to construct high active layered mesoporous calcium hydroxide. It was found that ethanol as a solvent could modify the lamellar morphology of calcium-based adsorbent, that the surfactant (CTAB) plays an important role in regulating the pore structure to obviously improve the desulfurization activity and utilization efficiency, and that its breakthrough sulfur capacity reaches 371.7 mg g−1 at 350 °C. The excellent desulfurization performance is attributed to the unique 2D lamellar morphology, high specific surface area, and mesopore structure of calcium hydroxide. Experimental and theoretical results reveal that SO2 is preferentially adsorbed on the surface of Ca(OH)2, and reacts with Ca(OH)2 to form CaSO3. CaSO3 is then oxidized by O2 in the presence of SO2 and CO2 to form CaSO4, and the presence of CO2 inhibited the catalytic oxidation of sulfite to sulfate by O2 from air. This synthesis strategy offers a facile method to construct efficient 2D adsorbent for SO2 removal.

Catalysts doi: 10.3390/catal16050390

Authors: Weon Bae Ko Aksaule Kydyrali Jeong Won Ko Ainur Zhambolova Nurbala Ubaidulayeva Bazarkhan Imangaliyeva Meruert Yerkibayeva Yerdos Ongarbayev

Zinc sulfide (ZnS) particles and zinc sulfide@multiwalled carbon nanotubes (ZnS@MWCNT) composites were synthesized and characterized using energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Raman spectroscopy. Photocatalytic degradation activity of methylene blue (MB) under ultraviolet (UV) at 254 nm light irradiation was assessed by UV-visible spectroscopy. The photocatalytic degradation efficiency of MB within 300 min reached 78.85% for ZnS particles and 82.85% for the ZnS@MWCNT composites. Therefore, in comparison to the ZnS nanoparticles, the hybrid ZnS@MWCNT composites exhibited higher photocatalytic degradation activity. The kinetics study for photocatalytic degradation of MB using both ZnS particles and hybrid ZnS@MWCNT nanocomposites followed the pseudo-first-order reaction rate law.

Catalysts doi: 10.3390/catal16050389

Authors: Abdulmohsen K. D. Alsukaibi Tse-Wei Chen Shen-Ming Chen Mohd Wajid A. Khan Subuhi Sherwani Khalid Almutair Faheem Ahmed Lassaad Mechi Murugan Velmurugan

In this study, an electrochemical sensor based on magnesium zirconate (MgZrO3) synthesized using a deep eutectic solvent (DES)-assisted approach was developed for the detection of dopamine. The structural and morphological properties of MgZrO3 were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, field-emission scanning electron microscopy, energy-dispersive spectroscopy, and elemental mapping. The electrochemical performance of the MgZrO3-modified glassy carbon electrode (GCE) was evaluated using cyclic voltammetry and differential pulse voltammetry. The MgZrO3/GCE exhibited an enhanced redox response and a reduced oxidation potential for dopamine in phosphate-buffered solution (PBS, pH 7.0), indicating improved electrocatalytic activity compared to the bare electrode. This improvement is attributed to the material’s increased active surface area and facilitated charge transfer kinetics. Under optimized conditions, the sensor showed a linear response over a concentration range of 0.3–80 µM, with a detection limit of 127 nM and quantification limit of 423 nM. The MgZrO3/GCE also demonstrated good selectivity in the presence of common interfering species and was successfully applied for dopamine detection in biological samples, with satisfactory recovery results. The findings presented here contribute to the growing body of knowledge in the field and open up new possibilities for the development of advanced electrochemical sensors for neurotransmitter detection in clinical and research settings related to Breast Cancer Treatment.

Catalysts doi: 10.3390/catal16050388

Authors: Abdulmohsen K. D. Alsukaibi Tse-Wei Chen Shen-Ming Chen Mohd Wajid A. Khan Subuhi Sherwani Mohammad Shahid Ali Ahmed Al Otaibi Faheem Ahmed Zoheb Karim

The quantitative analysis of cardio selective beta-blockers, such as the antihypertensive and antiarrhythmic medication acebutolol (ABT), is critical for biomedical and environmental monitoring. This study describes the development of a high-performance electrochemical sensing platform for ABT based on a screen-printed carbon electrode (SPCE) modified with a silver nanoparticle/hexagonal boron nitride (Ag NPs/h-BN) nanocomposite. The morphological and structural properties of the synthesized materials were examined by using a microscopic and spectroscopic techniques. The Ag NPs/h-BN/SPCE demonstrated exceptional electrocatalytic activity toward ABT oxidation, characterized by a significant reduction in overpotential and a substantial enhancement in peak current relative to unmodified and mono-component electrodes. This superior performance is attributed to the synergistic integration of Ag NPs and h-BN, which provides a high density of active sites, an expanded electroactive surface area, and accelerated charge transfer kinetics. Under optimized experimental conditions, the sensor exhibited a broad linear dynamic range of 0.01–284 μM, a remarkably low limit of detection (LOD) of 0.0049 μM, and a high sensitivity of 0.873 µA µM−1 cm−2 for ABT detection. Furthermore, the platform displayed excellent selectivity in the presence of common interfering species and robust reproducibility (RSD of 4.8%). The practical utility of the Ag NPs/h-BN/SPCE was successfully validated through the precise quantification of ABT in complex biological and environmental matrices. This work provides a versatile strategy for the rational design of metal nanocatalysts confined within h-BN frameworks for the development of advanced electrochemical diagnostic tools.

Catalysts doi: 10.3390/catal16050387

Authors: Natalia Martsinovich

The rapid technological development of our society has brought multiple challenges, such as environmental pollution and increased demand for clean water and energy [...]

Catalysts doi: 10.3390/catal16050386

Authors: Yousaf Khan Haleema Sadia Syed Zeeshan Ali Shah Muhammad Naeem Khan Amjad Ali Shah Naimat Ullah Muhammad Farhat Ullah Humaira Bibi Omar T. Bafakeeh Nidhal Ben Khedher Sayed M. Eldin Bandar M. Fadhl Muhammad Ijaz Khan

In the original publication [...]

Catalysts doi: 10.3390/catal16050385

Authors: Shenghao Li Siyu Song Chunlin Ke Zhengting Gu Mingzheng Liao Chao Wang

Formic acid (FA) has emerged as a promising liquid hydrogen storage material, yet efficient photothermal dehydrogenation catalysts with high activity and H2 selectivity remain challenging. Herein, a polymetallic synergistic PdCu/M-ZNC (where M represents the co-doped In, Sn and Mo species) is fabricated by molten-salt-assisted pyrolysis of ZIF-8 precursors followed by metal incorporation. The unique molten salt environment effectively preserves the porous architecture of ZIF-8, enabling the secure anchoring of PdCu alloy nanoparticles onto the carbonaceous matrix enriched with M-Nx coordination sites. Under light irradiation, the PdCu alloy sites kinetically accelerated the overall adsorption and activation of FA molecules. Based on empirical observations and corroborated by the established literature, this alloying effect was inferred to facilitate the C-H bond cleavage and HCOO* desorption processes. Concurrently, the M-Nx sites act as efficient electron transfer channels, facilitating the rapid coupling of photogenerated electrons with protons (H+) to evolve H2. Consequently, the optimal catalyst exhibits an enhancement in gaseous product yield (404.46 mmol/g/h) and H2 selectivity (67.49%) at 75 °C. This work offers a catalyst design that aligns with several principles of green chemistry: it maximizes the atom utilization of precious Pd, incorporates synergistic non-precious metals within MOF-derived frameworks to enhance stability, and leverages solar energy to drive hydrogen production under mild conditions, presenting a more sustainable pathway for hydrogen release from liquid carriers.

Catalysts doi: 10.3390/catal16050384

Authors: Sang-Hyeok Seo Donghyeok Kim Nahea Kim Myeung-Jin Lee Bora Jeong Bora Ye Heesoo Lee Hong-Dae Kim

N2O (Nitrous oxide) is a potent greenhouse gas with a global warming potential nearly 300 times that of CO2 and poses a critical environmental challenge, particularly in semiconductor and display manufacturing, where it is emitted during plasma processes. However, catalytic N2O abatement in O2-rich environments remains inefficient because O2 competitively occupies active sites and hinders the turnover of surface oxygen species. To clarify how support properties govern this inhibition, Co-based catalysts supported on beta zeolite, CeO2, and TiO2, together with unsupported Co3O4, were comparatively evaluated for direct N2O decomposition. Among them, Co/Beta exhibited the highest performance, achieving >95% N2O conversion at 450 °C in the presence of 5% O2 with excellent long-term stability. Co/Beta possessed a high specific surface area (649 m2 g−1) and a mesoporous framework that favored uniform Co dispersion and reactant accessibility, while its high Co2+/(Co2+ + Co3+) ratio (75.5%) and large fraction of chemisorbed oxygen species (79.9%) promoted oxygen-vacancy formation and facile oxygen exchange. These results indicate that the ability of Co/Beta to maintain high activity in the presence of oxygen stems from support-modulated cobalt surface states and enhanced oxygen turnover behavior. These findings provide a support-design principle for stable N2O decomposition under oxygen-containing exhaust conditions.

Catalysts doi: 10.3390/catal16050383

Authors: Bingquan Tian Haimin Ning Mingshan Jiang Guodong Jia Shiyi Zhao Guangsheng Wei Chunxiang Chen

The co-pyrolysis of Chlorella vulgaris (CV) and Eucalyptus branches (EP) offers a promising strategy to enhance bio-oil yield, improve resource utilization efficiency, and alleviate environmental pressures. In this study, the microwave-assisted co-pyrolysis of CV and EP at a mass ratio of 2:1 was investigated, focusing on the catalytic performance of Ni-X (X = Mg, Cu, Fe) bimetallic modified HZSM-5 zeolites. The effects of these catalysts on pyrolysis characteristics, product distribution, and bio-oil composition were systematically evaluated. Experimental results showed that the 15% Ni-Cu/HZSM-5 catalyst exhibited the best catalytic performance, achieving the highest bio-oil yield of 16.83%; it also elevated the Rm to 0.0687 wt.%/s and reduced Ts to 2084 s. Composition analysis revealed that Ni-Cu/HZSM-5 significantly promoted the formation of hydrocarbons, increasing their relative content from 11.59% (C2E1 Group) to 28.92%, while effectively suppressing the formation of nitrogen-containing compounds, reducing their content by 5.05%. Based on these results, a possible reaction pathway is proposed in which the Ni-Cu/HZSM-5 catalyst may enhance heteroatom removal through hydrodeoxygenation (HDO) at the Ni-Cu sites, followed by cracking and aromatization at the HZSM-5 acid sites. This effect may be complemented by preferential adsorption of oxygenated intermediates over nitrogen-containing species, which could help suppress the formation of nitrogenous heterocycles. This work provides theoretical guidance for the application of bimetallic zeolite catalysts in microalgae/lignocellulose co-pyrolysis, alongside a viable pathway for valorizing Eucalyptus by-products to produce high-quality bio-oil.

Catalysts doi: 10.3390/catal16050382

Authors: Shuyi Shang Jiahao Liu Jingshuai Liu Zhimei Guo Shuming Jin Chunhui Hu Fabin Zhang Kaili Nie

Albendazole (ABZ) exhibits poor oral absorption; therefore, ABZ was conjugated to cholic acid to engage the apical sodium-dependent bile acid transporter (ASBT) and promote ileal uptake. ABZ–linker–CA conjugates bearing amino-alcohol linkers (C4–C8) were evaluated by integrating synthetic feasibility, purification selectivity, and ex vivo performance. Thermal aminolysis in DMF (95 °C) produced ABZ–linkers in ~50% reaction yields (HPLC-assayed), with a minor ABZ-amine by-product consistent with a workup-sensitive isocyanate route. Immobilized-lipase screening identified Lipozyme RM IM as the most effective catalyst for CA esterification in CHCl3, showing a pronounced linker-length dependence (31% yield for C4, 25% for C6, and C8 ≤ 2.6% yield). Docking and molecular dynamics supported this trend by indicating productive binding geometries for C4/C6 but not for C8. A polarity-guided workup and silica-gel protocol enabled retrieval of unreacted intermediates and CA recycling, with cleaner separation for the C6 series. Ex vivo transport studies confirmed ASBT-mediated, linerixibat-sensitive ileal uptake, and protoscolex assays showed improved antiparasitic efficacy versus ABZ. Overall, ABZ-C6-CA offered the best balance of uptake, near-maximal efficacy, enzymatic accessibility, and separability, supporting its prioritization for scalable biocatalytic manufacturing.

Catalysts doi: 10.3390/catal16050381

Authors: Chanatip Sungprasit Kasidit Janbooranapinij Khin Kalyar Nyein Jidapa Chantaramethakul Wei Lun Ang Oratai Jongprateep Ratchatee Techapiesancharoenkij Gasidit Panomsuwan

Rapid and accurate urea detection is of considerable importance in environmental monitoring and biomedical analysis, as abnormal urea levels are associated with water contamination and various health conditions. In this study, a silver nanoparticle-decorated graphene oxide (Ag/GO) composite was synthesized via a simple chemical reduction method. The characterization results confirmed the successful formation of well-crystalline Ag nanoparticles (7.44 ± 1.46 nm) with uniform dispersion on GO, with a Ag loading of 39.1 wt%. The electrochemical performance for urea detection was evaluated in an alkaline medium (0.1 M NaOH) using cyclic voltammetry and chronoamperometry in a three-electrode system. The Ag/GO-modified glassy carbon electrode exhibited a strong electrocatalytic response toward urea oxidation, with a linear detection range of 1–10 mM. The sensitivity and limit of detection (LOD) were 36.8 μA mM−1 and 0.11 mM, respectively. The sensor also demonstrated excellent selectivity in the presence of common interfering species, including uric acid, ascorbic acid, and glucose, along with good reproducibility, repeatability, and stability. Furthermore, the practical applicability of the sensor was assessed in real samples, where satisfactory recovery was achieved in tap water, while reduced performance was observed in milk due to matrix effects. These findings indicate that the Ag/GO composite can serve as an effective alternative electrode material for non-enzymatic electrochemical detection of urea, particularly in wastewater and biological systems.

Catalysts doi: 10.3390/catal16050380

Authors: Hao Zhang Chao Ma Min Zhang Yangyang Yu Siyu Wei Yue Wang Zhiru Liu Huinan Li Tan Meng Ye Chen

Carbon monoxide (CO) is a highly toxic, colorless, and odorless gas posing significant risks to human health and the environment. Catalytic oxidation offers a promising, economically viable solution by converting CO into nontoxic CO2 under mild conditions without energy-intensive regeneration. However, existing MnO2-based catalysts often exhibit poor activity and stability in harsh environments, particularly at low temperatures and high humidity. In this study, we propose a Cu2+ ion-exchange modification strategy to activate lattice oxygen species in δ-MnO2, thereby significantly enhancing its low-temperature CO oxidation performance. Structural characterization by XRD and SEM confirms that Cu-doped δ-MnO2 retains its original birnessite-type structure and porous morphology. ICP-OES and XPS analyses verify that Cu2+ ions effectively replace interlayer K+ ions. The resulting MnO2-150Cu catalyst demonstrates exceptional activity, achieving 100% CO conversion at 40 °C in dry air and maintaining full conversion at 80 °C in the presence of 1.3 vol.% H2O at a weight hourly space velocity of 150 L/g·h. H2-TPR and O2-TPD results confirm that Cu doping enhances the reducibility and mobility of lattice oxygen. Furthermore, in situ DRIFTS analysis reveals that the migration of active oxygen species is the rate-limiting step at low temperatures. This work provides a novel and effective strategy for activating lattice oxygen in MnO2-based catalysts, offering a promising pathway for developing high-performance materials for low-temperature CO oxidation under practical environmental conditions.

Catalysts doi: 10.3390/catal16050379

Authors: Roxana Jijie Marius Dobromir Teodora Matei Ioana-Laura Velicu Valentin Crăciun Georgiana Bulai Vasile Tiron

Piezo-enhanced photocatalysis is progressively considered an eco-friendly technology for contaminant removal, harvesting not only solar energy but also mechanical vibrations found in nature. Multiferroic materials present a coupled effect of various properties and can potentially increase the applicability of this process. In this study, Cr- doped bismuth ferrite thin film was deposited on SrTiO3 substrate by HiPIMS, and its photo-, piezo-, and piezo-photocatalytic efficiencies in Rhodamine B (RhB) degradation were analyzed. The highest removal percentage was found under the simultaneous exposure of visible light and mechanical vibrations, reaching 86.2% after 180 min. The calculated efficiencies for photo- and piezocatalysis were 12.2% and 83.7%, respectively. The rate constant (k) for piezo-photocatalysis was 16.1 times higher than that found during photocatalytic experiments. To assess the contribution of each reactive species to the decomposition process, different reagents were added to the Rhodamine B contaminated solution. The results revealed that when p-benzoquinone was used, the degradation efficiency declined significantly from 86.2% to 37.6%, suggesting that superoxide radicals (O2•−) play a key role in decomposing RhB molecules. The structural, chemical, optical, and ferroelectric changes caused by the catalytic processes were analyzed and linked to the proposed degradation mechanisms. The poor photocatalytic efficiency was linked to an improper band structure and an improper polarization orientation of the ferroelectric domains in the as-deposited film. The degradation mechanisms in piezo-photocatalysis were driven partly by the band bending caused by mechanical vibrations and partly by the reorientation of the induced polarization of the domains in the unstrained film.

Catalysts doi: 10.3390/catal16050378

Authors: Yuan Tian Xian Liu Tianqi Ren Wen Pan Qiyao Zhang

The widespread presence of ciprofloxacin (CIP) in aquatic environments threatens ecological and public health, yet conventional treatment processes fail to remove such persistent contaminants. Conventional solvothermal synthesis of Bi-doped g-C3N4 photocatalysts involves complicated procedures and low productivity. Herein, we employ a single-step, template-free and solvent-free green calcination method to construct Bi3+-modified g-C3N4 with strong Bi-N coordination interactions. A series of Bi/g-C3N4 photocatalysts with Bi-doping mass ratios of 0.09–0.34 wt% was prepared, and the structure–performance relationship as well as the surface–interface reaction mechanism for ciprofloxacin (CIP) degradation were systematically elucidated. Experimental results confirm that Bi3+ incorporates into the lattice via Bi-N coordination bonds with nitrogen in the g-C3N4 framework, which narrows the band gap, suppresses photogenerated carrier recombination, and constructs a loose porous morphology beneficial for increasing specific surface area and active sites. Under optimal conditions, 15Bi/g-C3N4 achieves 97.6% degradation of 15 mg L−1 CIP within 90 min, which is 13.7% higher than that of pristine g-C3N4. The effects of catalyst dosage, initial pH, CIP concentration, common coexisting ions, and different real water matrices on the degradation performance were systematically investigated. Radical quenching experiments combined with ESR characterization confirm that h+ is the dominant reactive species responsible for CIP degradation. This green, simple and scalable method yields uniform products, and the resulting materials exhibit high efficiency, economic feasibility and environmental safety, demonstrating promising potential for antibiotic wastewater treatment.

Catalysts doi: 10.3390/catal16050377

Authors: Sining Wei Mahwish Aziz Yilin Zhang Jian Xiong Cheng Cheng Bin Wu

This study addressed the issue of insufficient activity in CALB lipase during the catalytic synthesis of key chiral intermediates for moxifloxacin. A structure-guided protein engineering strategy was employed to systematically modify its functional domains. Through molecular dynamics simulations of CALB-I189K, multiple regions exhibiting high conformational flexibility were preliminarily identified. Subsequently, by integrating 3D structural alignment with active site pocket distance analysis, the functionally most critical region (143–146) was selected. A site-directed saturation mutation library was constructed specifically targeting this region. Building upon the previously reported CALB-I189K, a mutant I189K/L144R/A146K was ultimately obtained through high-throughput screening combined with chiral HPLC validation. This mutant maintains excellent stereoselectivity (E = 206.52) while enhancing catalytic efficiency (kcat/Κm) to 273.73 min−1·mM−1, approximately 4.5-fold that of I189K. At a substrate concentration of 1 M, it achieves 50% conversion within 2.6 h, demonstrating kinetic resolution capabilities approaching industrial standards. Molecular simulation analysis indicates that the L144R and A146K mutations synergistically enhance catalytic performance primarily by optimizing spatial distances between catalytic residues. This study not only provides a high-performance catalyst for the efficient biosynthesis of moxifloxacin chiral intermediates but also offers new insights for enzyme rational design based on dynamic structural information.

Catalysts doi: 10.3390/catal16050376

Authors: Sofía Essounani-Mérida Sergio Molina-Ramírez Marina Cortés-Reyes Concepción Herrera Elisabetta Finocchio María Ángeles Larrubia Luis J. Alemany

The CO2 storage–regeneration (CO2-SR) process represents a promising strategy for integrating CO2 capture and catalytic conversion within a single cyclic operation using multifunctional catalysts. In this concept, CO2 is first stored on basic sites and subsequently converted through methane activation, enabling the coupling of CO2 capture and reforming reactions in a single reactor. In this work, a series of unsupported Ni–Ba catalysts were investigated as model multifunctional materials for the CO2-SR process. Catalysts with different Ni/Ba ratios were prepared to analyze how the distribution of storage and catalytic sites influences the cyclic CO2 capture–conversion behavior. In addition, Rh was introduced as a promoter either during synthesis by co-precipitation or ex situ by impregnation, allowing to evaluate the influence of Rh location and surface enrichment on the catalytic properties. Rh incorporation in the NiBa catalyst (Ni/Ba = 10/1 and Ni/Rh = 100/1) increased the specific surface area (BET area 64 m2·g−1 vs. 55 m2·g−1 for NiBa) and reduced the NiO crystallite size from 250.4 Å to 231.5 Å, indicating improved dispersion of the metallic phase. XPS analysis revealed the coexistence of Rh0 and Rh3+ species, suggesting that Rh acts as a redox mediator that facilitates hydrogen activation and promotes hydrogen spillover to neighboring Ni sites. Raman and CO2-TPD results show that Ba-derived domains stabilize carbonate species responsible for CO2 storage, while Rh enhances catalyst reducibility and modifies the kinetics of carbonate decomposition during the regeneration stage. Transient CO2–CH4 pulse experiments demonstrate that the CO2-SR process proceeds through a dynamic surface cycle involving reversible carbonate formation on Ba-derived basic sites coupled with methane activation on Ni-containing interfacial sites. The results indicate that catalyst performance is governed by a hierarchical surface architecture composed of Ni–O–Ba interfacial domains, reversible Ba–O–Ba carbonate storage sites, and more stable Ba-rich domains. The distribution of these domains, controlled by the Ni/Ba ratio and the dispersion of the metallic phase, determines the reversibility of carbonate formation and the efficiency of the cyclic CO2 storage–regeneration process.

Catalysts doi: 10.3390/catal16050375

Authors: Wenqing Chen Zihao Zhang Xuwen Gao Zeng Liu Tao He Zhiqi Wang Jianqing Li Jinzhi Zhang Ruidong Zhao Jinhu Wu

The rational design of oxygen carriers (OCs) is critical for enhancing biomass chemical looping gasification (BCLG) performance. This work systematically investigated the effects of different supports (Al2O3, ZrO2, TiO2, SiO2) on the performance of NiFe-based OCs with oxidation and catalytic reforming functions. The gasification reactivity and support-active phase interaction of OCs in both oxidized and reduced states were evaluated. XRD, H2-TPR, XPS, and SEM techniques were employed to characterize the phase composition, synergistic interactions, and surface morphology. The results showed that NiFeAl exhibited the optimal gasification performance in both oxidized and reduced states, achieving a syngas (H2 + CO) yield of approximately 1.4 m3/kg (dry walnut shell). NiFeAl featured a higher Fe binding energy, abundant cavity structures, and the uniform dispersion of Ni and Fe on Al2O3, which confirm the formation of an appropriately strong Ni-Fe-Al ternary system. In contrast, NiFeZr suffered from the higher CO2 yield, attributed to the over-oxidation caused by the weak interactions. NiFeTi and NiFeSi had lower syngas yields due to their poor reducibility induced by excessively strong interactions. This work verifies that moderate support-active phase interactions in OCs are optimal for BCLG.

Catalysts doi: 10.3390/catal16050374

Authors: Fukang Hou Dan Wu Pengcheng Chen Pu Zheng

Trans-anethole oxygenase (TAO) exhibits broad arylpropene substrate specificity but has low activity in converting isoeugenol to high-value vanillin. Herein, we employed computer-aided rational design to engineer TAO from Pseudomonas putida (PpTAO) for enhanced catalytic efficiency toward isoeugenol. Structural modeling and AlphaFold 3 docking identified two key catalytic residues, Arg86 and His118. Through substrate channel engineering and computation-guided mutagenesis, a series of targeted variants were constructed. Three variants, H93A, Q207R/G249C, and I59T/F62T, showed significant improvements in whole-cell performance, with activity increases of 1.8-, 2.13-, and 4.83-fold over the wild type (WT), respectively. Purified enzyme kinetics corroborated these findings, as reflected in kcat/Km values that reached 1.6, 2.1, and 4.7 times that of the WT. Mechanistic molecular dynamics simulations revealed that H93A enhances activity by widening the access tunnel, whereas Q207R/G249C exerts beneficial distal effects. Notably, the I59T/F62T variant significantly increases substrate affinity by optimizing hydrophobic interactions within the binding pocket. These results validate the efficacy of computational modeling in enzyme redesign and provide a robust biocatalyst for the sustainable biosynthesis of vanillin.

Catalysts doi: 10.3390/catal16050372

Authors: Jiangbo Yu Dihong Zhang Yuhan Xiong Jie Liu Haoyang Shen Zuo Wen Haoqin Xu Zhanchao Wu Zhuangzhi Han Tiantian Zhang Shaoping Kuang

A Ce-doped photocatalytic composite with easy solid–liquid separation capability was prepared and a heterojunction was constructed between BiVO4 and Fe3O4 via a co-precipitation method. A variety of characterization techniques were employed, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy (UV-vis), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS), as well as other related methods. Its photocatalytic performance for the degradation of Rhodamine B (RhB) was also studied. The results indicate that the photocatalytic efficiency of BiVO4/Fe3O4 is 1.4 times that of the pure BiVO4 matrix. In particular, the photocatalytic efficiency of Ce1.5%-BiVO4/Fe3O4 was 2.2 times higher than that of the pure BiVO4 matrix, and a 100% degradation rate of RhB was achieved within 30 min. The introduction of Fe3O4 not only forms a heterojunction with BiVO4, increasing the active sites and surface oxygen vacancies of the material and effectively suppressing the recombination of photogenerated electron (e-)-hole (h+) pairs, but it also enables the rapid separation of the material from the wastewater solution by the magnetic properties of Fe3O4. Additionally, the partial substitution of Ce for Bi in the BiVO4 lattice reduces the bandgap energy, which enhances the utilization efficiency of visible light and improves the photocatalytic performance of the composite material. The mechanism of RhB degradation by Ce1.5%-BiVO4/Fe3O4 composite materials is also analyzed in this study. Quenching experiments and EPR tests revealed that h+ and ·O2- were the primary reactive species in the degradation process.

Catalysts doi: 10.3390/catal16050373

Authors: Change Yao Jun Zhu Shian Wang Jiayi Liao Lin Li Jiahao Jiang Run Cai Wenjie Bi Xin Chen Zhong Ma

Pt–transition metal intermetallic compounds have been recognized as promising catalysts for oxygen reduction reaction (ORR). However, further enhancing the activity and durability of this kind of catalyst is still necessary. Herein, we report a novel L10-type PtFe intermetallic nanoalloy with the partial substitution of Fe sites by La as a highly active and stable catalyst towards ORR. This new intermetallic nanoalloy retains an ordered structure after the incorporation of La confirmed by XRD, XPS and TEM results and the ordered PtFe0.5La0.5 nanoparticles are embedded in porous carbon (L10-PtFe0.5La0.5@C) in very uniform particle size of around 2 nm. This L10-PtFe0.5La0.5@C catalyst exhibits a half-wave potential of 933 mV, which is about 12 mV and 70 mV higher than those of L10-PtFe@C and commercial Pt/C catalysts, respectively. Moreover, it also achieves an enhanced mass activity of 0.79 A mgPt−1 at 0.90 V, which outperforms the performance of commercial Pt/C (0.10 A mgPt−1). In addition, it also shows excellent stability with only 3 mV negative shift in half-wave potential after 20k CV cycles of accelerated durability testing. This high activity and stability may be attributed to the incorporation of La in the PtFe lattice, which induces the formation of a compressively strained Pt overlayer in acidic media which not only tunes the surface strain of Pt sites but also possesses robust resistance to the dissolution of Fe and La. This work also provides a new direction for the development of Pt-based intermetallic catalysts for efficient catalysis applications.

Catalysts doi: 10.3390/catal16050371

Authors: Xiao-Long Han Zi-Ming Wang Wen-Hui Xue Zhi-Yuan Liu Wen-Xia Song Guo-Dong Liu

Pyranose oxidases (POXs, EC 1.1.3.10) are a class of fungal FAD-dependent oxidoreductases with potential for lignocellulosic bioconversion because they generate H2O2 during sugar oxidation. Despite their known catalytic properties, the role of these enzymes in promoting lignocellulose enzymatic saccharification remains largely unexplored. In this study, POXs from Phanerochaete chrysosporium (PcPOX) and Trametes versicolor (TvPOX) were comparatively evaluated through biochemical characterization, kinetic analysis, molecular simulation, and supplementation for lignocellulose hydrolysis. PcPOX exhibited a broader substrate spectrum and a slightly higher optimum temperature, whereas TvPOX demonstrated greater stability under acidic and hydrolysis-relevant conditions and a longer half-life at 50 °C. TvPOX also showed a numerically lower apparent Km toward D-glucose, while the apparent catalytic efficiencies were comparable between the two enzymes. Molecular simulation results suggested more stable glucose binding in TvPOX. Accordingly, TvPOX was selected for hydrolysis experiments and was shown to increase the measured glucan conversion of phosphoric acid-swollen cellulose, Avicel, and corncob residue. Mixture design analysis further indicated that this positive effect depended on balanced peroxide regulation, with low catalase supplementation providing better performance. These results identify TvPOX as a promising auxiliary enzyme for cellulase-based lignocellulosic saccharification.

Catalysts doi: 10.3390/catal16040370

Authors: Hussain S. AlShahrani Hadi M. Marwani Khalid A. Alzahrani Kahkashan Anjum Anish Khan

The world’s growing need for energy, fueled by industrial expansion and a rising population, continues to be a challenge for the scientific community. The heavy reliance on fossil fuels that contribute to environmental degradation and public health concerns, is shifting toward sustainable alternatives, with hydrogen production via advanced catalysts as an energy source emerging as a promising solution. This transition addresses the challenges posed by harmful combustion emissions. In this study, we developed an innovative PANI@Cu-NA-MOF nanocomposite catalyst through a sol–gel synthesis approach that strategically integrates conducting polymers with metal–organic frameworks. The catalyst was characterized using different sets of techniques. Surface morphology and elemental composition were investigated using SEM-EDX, while structural analysis was carried out with FTIR that helped to identify the chemical bonds and functional groups, and UV-Vis spectroscopy provided information on its light absorption properties. In addition, TGA was used to evaluate thermal behavior, and XPS offered detailed surface chemical analysis. It was observed by morphology that PANI@Cu-NA-MOF is a noncapsular-like structure. It is thermally highly stable; a TGA study showed that up to 550 °C, almost 2.5% of weight was lost. The single peak in UV-Vis is the preparation of a successful composite. XPS and FTIR reveal the required peaks of functional groups and elements. The PANI@Cu-NA-MOF composite turned out to be quite effective for water electrolysis, requiring an overpotential of just 0.47 V to drive the reaction. When tested against the reversible hydrogen electrode, we observed onset potentials of 1.6 V/RHE for the oxygen evolution reaction and 0.2 V/RHE for the hydrogen evolution reaction. What makes this particularly interesting is that such performance significantly cuts down on the energy needed for electrolysis, which could make hydrogen production much more practical. Since hydrogen burns cleanly and offers a real alternative to fossil fuels, having an efficient catalyst like this brings us one step closer to sustainable energy.

Catalysts doi: 10.3390/catal16040369

Authors: Marietta Hakarová Marek Bučko Štefánia Hrončeková Alica Vikartovská Dušan Chorvát Anton Mateašik Pavla Hájovská Peter Gemeiner

Jet-cutting—the most powerful immobilization technique—was utilized for the entrapment of recombinant E. coli cells expressing a cascade of enzymes, including alcohol dehydrogenase, enoate reductase, and cyclohexanone monooxygenase, within mechanically reinforced barium–calcium alginate beads. Cost-effective alginate beads with entrapped cells were applied in a model process for the production of the industrially relevant ε-caprolactone under bioreactor-controlled conditions, enabling parallel repeated biotransformations. Immobilization resulted in a reduced rate of cell deactivation over four biotransformation cycles, leading to overall ε-caprolactone yield increases of 36% using 0.55 mm beads and 22% using 0.9 mm beads compared to the use of free cells. Additionally, the model bioprocess was employed to investigate the metabolic adaptation of cells to immobilization and repeated biotransformations using viability assays and spectrally resolved confocal microscopy. These measurements, conducted for the first time throughout the entire cellular life cycle, clearly demonstrated that the cells retained high viability during cultivation, immobilization, and repeated use in biotransformations. Moreover, based on characteristic spectral shifts, advanced analysis via spectrally resolved confocal microscopy revealed distinct mechanisms of metabolic adaptation in entrapped cells versus free cells during repeated cascade reactions in parallel bioreactors.

Catalysts doi: 10.3390/catal16040368

Authors: Zhebiao Xu Siyu Song Zhuangjia Chen Wenzhuo Wang Yushen Huang Fudong Bai Riyang Shu Zhipeng Tian Chao Wang

The development of high-performance and sustainable carbon electrodes is increasingly important for next-generation supercapacitors, yet controlling heteroatom doping and hierarchical pore evolution in biomass-derived carbons remains a key challenge. Lignin, as an abundant aromatic biopolymer, offers a structurally rich platform for designing functional carbons, but its rigid cross-linked architecture limits precise pore regulation and efficient nitrogen incorporation. In this work, nitrogen-doped hierarchical porous carbons were engineered from enzymatically treated lignin through a synergistic urea-assisted nitrogen doping and KOH activation strategy. The urea–KOH co-activation drives the coordinated evolution of micropores and mesopores. This approach yields an optimized carbon material possessing a high BET surface area of 2569 m2 g−1, an interconnected micro–mesoporous architecture, and a favorable distribution of pyridinic, pyrrolic, and graphitic nitrogen species. The engineered pore hierarchy is correlated with enhanced ion transport kinetics, as evidenced by a high b value of 0.99 and a capacitive contribution of 98.5% at 100 mV s−1; nitrogen functionalities introduce redox-active sites and improve interfacial wettability. As a result, the selected material delivers a high specific capacitance of 221 F g−1 at 0.5 A g−1, strong rate capability with 84.4% retention at 20 A g−1, and excellent cycling durability with 90.7% capacitance retention after 50,000 cycles. This study demonstrates a potentially mechanistically informed, scalable pathway for coupling enzymatic structural regulation with chemical activation, offering a sustainable route for transforming lignin into high-value carbon electrodes suitable for advanced supercapacitor applications.

Catalysts doi: 10.3390/catal16040367

Authors: Ghazala Muteeb Youssef Basem Abdel Rahman Alaa Mahmoud Hassan Ismail Mohammad Aatif Mohd Farhan Sheeba Kumari Doaa S. R. Khafaga

Nano–bio hybrid catalysts have emerged as a promising platform for sustainable energy conversion by integrating the high selectivity of enzymes with the structural robustness and conductivity of nanomaterials. In recent years, the growing demand for clean energy technologies has driven the development of biohybrid systems capable of efficient electron transfer, enhanced catalytic activity, and improved operational stability. This review comprehensively discusses the design principles, mechanistic foundations, and performance metrics of enzyme–nanomaterial interfaces for energy-related applications. We first outline the fundamentals of enzymatic redox catalysis and the limitations of free enzymes in practical systems. Subsequently, we examine the functional roles of nanomaterials including carbon-based materials, metal and metal oxide nanoparticles, and two-dimensional platforms such as MXenes in facilitating enzyme immobilization and promoting direct or mediated electron transfer. Special emphasis is placed on engineering strategies at the bio–nano interface, including immobilization techniques, surface functionalization, and structural tuning to optimize catalytic efficiency. The review further highlights representative hybrid systems based on laccase, glucose oxidase, peroxidase, and hydrogenase enzymes, and evaluates their applications in biofuel cells, solar–bio hybrid systems, green oxidation reactions, and self-powered biosystems. Stability challenges, deactivation mechanisms, and enhancement strategies such as polymer coatings, cross-linking, and nanoconfinement are critically analyzed. Finally, emerging directions including artificial enzymes, AI-guided catalyst design, and self-healing bioelectrodes are discussed to provide a forward-looking perspective on next-generation sustainable bioelectrocatalytic systems.

Catalysts doi: 10.3390/catal16040366

Authors: Yujian Wu Wenwen Liu Linhong Xie Leihe Cai Haowei Li Shengxian Xian Zheng Liang Qing Xu Chunbao Xu

Thermochemical/catalytic co-processing of biomass and solid wastes is a promising route for waste valorization, low-carbon energy recovery, and the co-production of fuels, chemicals, and carbon materials. Conventional pathways, including pyrolysis, gasification, liquefaction, and carbonization, provide the basic framework for mixed-feed conversion. Emerging routes, such as flash Joule heating, microwave-assisted conversion, plasma processing, supercritical water treatment, solar-driven systems, and machine-learning-assisted optimization, further expand opportunities for process intensification and selective upgrading. Owing to feedstock complementarity, including hydrogen donation from plastics, catalytic effects of ash minerals, and interactions among reactive intermediates, co-processing can enhance deoxygenation, hydrogen generation, aromatization, and carbon utilization. Major challenges remain, however, including feedstock heterogeneity, reactor scale-up, catalyst stability, and the limited transferability of laboratory-scale synergy to realistic waste streams. Future progress should therefore focus on continuous validation, mechanistic clarification, and integrated techno-economic, life-cycle, and data-driven assessments.

Catalysts doi: 10.3390/catal16040365

Authors: Shahina Riaz Ziyauddin S. Qureshi Muhammad Naseem Akhtar Essra Altahir Abdullah H. Albin Saad Aaron C. Akah Mohammad A. Alkhunaizi Rashed M. Aleisa Omar Y. Abdelaziz

Biodiesel is a sustainable and promising alternative energy source produced from renewable raw materials using various methods. One effective approach is simultaneous esterification and transesterification, which relies on suitable catalysts that can be either homogeneous or heterogeneous. Homogeneous catalysts (acid or base) offer high activity but are corrosive and difficult to recover, necessitating energy-intensive processes such as aqueous quenching and neutralization, which can lead to soap formation and stable emulsions. By comparison, heterogeneous catalytic systems overcome many of these challenges due to their ease of recovery, reusability, and simplified product separation, which collectively enhance economic viability and environmental sustainability. This review highlights recent progress in the application of zeolite-based solid catalysts for biodiesel synthesis, with particular emphasis on their use in converting waste cooking oil and other low-cost feedstocks, including non-edible oils, non-food biomass sources, algal resources, and genetically engineered microorganisms. Key factors such as catalytic activity, selectivity, catalyst loading, and reusability are discussed, highlighting the advantages of zeolites due to their unique crystal structure, high thermal stability, and ease of product recovery. Overall, this review underscores the challenges and opportunities in zeolite-based catalysis to provide a comprehensive understanding of its potential to enhance the efficiency and scalability of biodiesel production.

Catalysts doi: 10.3390/catal16040364

Authors: Lihui Wang Shao Zhang Mingming Wang Zhigang Wang Xiaoyao Tan

The high-temperature proton ceramic membranes with simultaneous separation of hydrogen and oxygen exhibit promising applications in the catalytic conversion field. However, their separation performance often relies on external electrical circuits, which limits practical application. To overcome this limitation, doping strategies have emerged as a viable approach to develop triple-conducting (H+/e−/O2−) membranes for simultaneous hydrogen and oxygen separation in non-electrochemical mode. In this study, honeycomb-structured hollow fiber membranes were fabricated, and the effects of varying Fe3+ and Y3+ doping concentrations on hydrogen and oxygen permeation fluxes were systematically investigated. At the Fe3+ doping level of 0.2 mol, the oxygen permeation flux of 0.692 mL min−1 cm−2 in BaCe0.6Zr0.2Fe0.2O3−δ (BCZF) was achieved at 1000 °C, while the hydrogen permeation flux was 0.201 mL min−1 cm−2. The BaCe0.55 Fe0.05Zr0.2Y0.2O3−δ (Fe-BCZY) hollow fiber membrane can enhance the hydrogen permeation flux by 75% at 1000 °C. Furthermore, during the simultaneous permeation of hydrogen and oxygen, a 1.7-fold enhancement in hydrogen permeation performance was achieved for the Fe-BZCY hollow fiber membrane at 1000 °C, and with oxygen permeation flux of 1.76 mL min−1 cm−2 at the same temperature. More significantly, a hydrogen permeation flux of 0.34 mL min−1 cm−2 can be achieved at 700 °C under simultaneous hydrogen and oxygen permeation, which is favorable for the application of membrane reactors in catalytic reactions.

Catalysts doi: 10.3390/catal16040363

Authors: Jia Wei Tai Yean Ling Pang Wei-Hsin Chen Yi-Kai Chih Steven Lim Woon Chan Chong

A highly efficient ZnO/biochar (ZnO/BC) composite was synthesised from phytoremediation residue and evaluated for the advanced sonocatalytic degradation of malachite green in aqueous solutions. The structural, chemical, and morphological properties of the composite were characterised using physicochemical techniques, confirming the successful impregnation of zinc oxide (ZnO) onto the biochar matrix. The catalytic performance of the synthesised composite in treating malachite green was systematically evaluated and optimised using response surface methodology (RSM), specifically a central composite design (CCD), to analyse the interactive effects of initial dye concentration, catalyst loading, and ultrasonic irradiation time. The developed model exhibited a high coefficient of determination (R2) of 0.996 and an adequate precision of 62.67, confirming the model’s significance. Optimal degradation was observed at an initial malachite green concentration of 73.71 mg/L, a catalyst loading of 0.527 g/L, and a sonocatalytic treatment duration of 18.7 min. Furthermore, the ZnO/biochar composite demonstrated excellent mineralisation capabilities, with chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies reaching 89.79% and 68.43%, respectively, after 60 min of treatment. These findings establish ZnO/BC as a highly active sonocatalyst, offering a promising approach for the remediation of organic dyes in industrial wastewater treatment.

Catalysts doi: 10.3390/catal16040362

Authors: Xiong Peng Zhongwei Yu Yongfen Zhang Hongquan Liu Yanpeng Yang Jinzhi Li Aizeng Ma

The rational design of supported Lewis acid catalysts is frequently impeded by an incomplete understanding of how the support’s synthetic history governs its intrinsic acidity and catalytic efficacy. Herein, we elucidate the structure–property–performance relationship linking the aging dynamics of a boehmite precursor to the activity of the resultant chlorinated alumina (Al2O3–Cl) catalyst in n-butane isomerization. Using n-butane as the probe feedstock, we investigated how alumina supports with distinct physicochemical properties regulate the performance of Al2O3–Cl catalysts for n-butane isomerization. By systematically adjusting the aging parameters (stirring rate, temperature, and time), we reveal that the structural evolution of the alumina support transitions from initial particle aggregation to Ostwald ripening and surface reconstruction. A decisive structure–performance correlation is identified: precursor synthesis conditions govern both the population and accessibility of specific surface hydroxyls (notably Type II terminal OH groups), which act as anchoring sites for the generation of active Lewis acid centers upon chlorination. Optimal aging parameters (300 rpm, 90 °C, 6 h) promote the formation of a hierarchical pore architecture with a maximized density of accessible hydroxyls, thereby affording enhanced Lewis acidity and superior isomerization activity. This work provides a fundamental framework for tailoring solid acid catalysts by precisely engineering the precursor architecture.

Catalysts doi: 10.3390/catal16040361

Authors: Felice Kubale Herman A. Murillo Alexis Debut Sebastian Ponce

The development of selective and sustainable catalysts is essential to enable the chemical recycling of mixed plastic waste. In this work, calcium-modified biochars derived from cocoa pod husk (CPH) and palm kernel shell (PKS) were prepared for treating a mixture of poly(ethylene terephthalate) (PET) and poly(lactic acid) (PLA). The aim was to separate the mixture through the PLA methanolysis, while maintaining the PET unreacted for a potential physical recycling. Biochar was ex situ modified with calcium precursor using a value-added concentrate recovered from the hydrothermal treatment of Jatropha fruit husk. Subsequently, a pyrolysis step was further applied to convert the calcium species into CaO, which is the active phase for the methanolysis reaction. Structural, microscopic, and spectroscopic analyses revealed that the carbon matrix strongly influences the evolution and stabilization of calcium phases during pyrolysis and post-treatment. CPH-derived biochars promoted the formation of highly dispersed CaO, whereas PKS favored the growth of larger, less reactive Ca(OH)2 domains. As a result, the CPH_Ca10 (i.e., 10% desired calcium loading based on CPH-biochar mass) catalyst exhibited superior basicity and catalytic activity, achieving near-complete PLA conversion under mild conditions (90–110 °C) depending on the system with only 2 wt.% catalyst. Importantly, under these mild conditions, PET remained chemically intact, demonstrating the process’s high selectivity and applicability to mixed bioplastic–fossil plastic streams. This study highlights a circular, low-carbon route to producing effective Ca-based catalysts from agricultural residues. It establishes a promising strategy for selective depolymerization and separation in complex plastic waste systems.