Catalysts doi: 10.3390/catal16070596

Authors: Bo Meng Tingtao Liu Yingning Wang Shaopeng Yu

Advanced oxidation processes (AOPs) are widely applied to degrade recalcitrant organic contaminants in municipal effluents, industrial wastewaters, and water-reuse streams. Their deployment, however, remains constrained by matrix scavenging, high energy or reagent demand, catalyst/electrode ageing, and the possible formation of toxic transformation products. Artificial intelligence and machine learning (AI/ML) have been proposed as tools for prediction, optimization, catalyst discovery, mechanism inference, and process control, but high accuracy on curated laboratory datasets is often confused with actionable knowledge for real treatment systems. This narrative review evaluates AI/ML-enabled AOPs through an evidence-to-deployment framework built on three principles: real wastewater is treated as the primary inference domain; mechanistic claims are graded according to convergent evidence; and AI/ML contributions are linked to explicit decisions rather than to model accuracy alone. We argue that progress depends less on black-box complexity than on standardized reporting, benchmark matrices, curated datasets, uncertainty-aware validation, and pilot-scale demonstrations that satisfy contaminant removal, energy efficiency, byproduct safety, and operational constraints simultaneously. A six-gate decision framework and a targeted research agenda are proposed to guide future studies toward deployment-grade evidence.

Catalysts doi: 10.3390/catal16070595

Authors: Jianghua Yang Peihang Wu Yanhong Li Shujuan Zhang

Semiconductor–biological hybrid systems (SBHS) have emerged as a disruptive technology for solar-driven chemical manufacturing, effectively bypassing the thermodynamic bottlenecks of natural photosynthesis. However, the aggressive pursuit of record-breaking solar-to-chemical conversion efficiencies has inadvertently fostered an efficiency trap. A profound interdisciplinary schism exists wherein the acute environmental toxicity and long-term interfacial instability of these hybrid architectures are frequently overlooked. This review provides a critical appraisal of the oft-ignored environmental risks inherent in current SBHS designs. We systematically dissect the heavy metal leaching toxicity of first-generation inorganic photosensitizers and unveil the complex, bidirectional degradation mechanisms at the abiotic–biotic interface. Specifically, we highlight the dual threats of photogenerated reactive oxygen species inducing cellular oxidative stress and active, microbially induced material dismantling via reductive dissolution driven by extracellular electron transfer. To navigate beyond this purely performance-driven paradigm, we propose a multidimensional, standardized evaluation matrix that systematically balances catalytic efficiency with biological safety and life-cycle sustainability. Ultimately, this review offers a comprehensive roadmap to transition biohybrid platforms from fragile laboratory concepts into robust, scalable, and ecologically benign negative-emission technologies.

Catalysts doi: 10.3390/catal16070594

Authors: Renata Bodnarova Serhii Vorobiov Miroslava Kozejova Maksym Lisnichuk Elias Assayehegn Dominik Volavka Vladimír Komanický

In this work, ternary Mo–Ni–X (X = Al, Co, Cr, Cu, Fe, W) thin films with nominal composition Mo80Ni10X10 (at. %) were prepared by magnetron sputtering and evaluated as electrocatalysts for the hydrogen evolution reaction (HER) in alkaline media. The influence of alloy composition, substrate type, and deposition temperature on catalytic performance was systematically investigated. Electrochemical screening revealed a strong dependence of HER activity on both substrate conductivity and ternary alloying, with Al-, Cr-, and W-containing systems showing the best performance on glassy carbon substrates. This highlights the importance of interfacial charge-transfer efficiency in determining catalytic behavior. The Mo80Ni10Cr10/GC system was selected for detailed analysis. Deposition temperatures ≥ 500 °C resulted in enhanced HER activity, reaching an overpotential of η10 = −222 mV at j = −10 mA cm−2. The improved performance is attributed to temperature-induced microstructural optimization and electrochemically driven surface reconstruction, leading to the formation of a Ni-enriched active interface. AFM analysis confirmed surface restructuring during operation, with roughness increasing from ~1 to ~3 nm, indicating the formation of additional electrochemically accessible active sites. XPS results suggest partial depletion of Mo during cycling, while Cr mainly contributes to structural stabilization of the evolving thin film. Overall, the results demonstrate that HER performance is governed by the coupled effects of alloy composition, substrate-dependent charge transport, and in situ surface reconstruction. This work highlights magnetron sputtering as a scalable approach for designing homogeneous noble-metal-free thin-film electrocatalysts with tunable activity.

Catalysts doi: 10.3390/catal16070593

Authors: Daniel Sanchez-Martinez Sergio Obregón Arturo A. Castillo-Guzman José A. Loyola-Rodríguez Diana B. Hernández-Uresti

Metal-free polymeric semiconductor graphitic carbon nitride (g-C3N4) was synthesized via thermal polycondensation using cyanamide with PVP as a medium, using SiO2 nanospheres as sacrificial templates to suppress bulk agglomeration. Structural analysis using X-ray diffraction (XRD) confirmed the conservation of the g-C3N4 structure, while diffuse reflectance UV-Vis spectroscopy (DRS) showed that there is a slight change in optical absorption, modifying the band gap energy of g-C3N4 with the addition of SiO2. Transmission electron microscopy (TEM) evidenced the formation of interconnected porous architectures, facilitating charge migration. Photocatalytic activity was evaluated under simulated solar irradiation using acetaminophen (ATP) as a model pharmaceutical pollutant. Kinetics experiments demonstrated that the sample containing 7% SiO2 nanospheres achieved 65% degradation for 180 min. The best photocatalytic performance is attributed to the pore volume, which favors better adsorption, facilitating the degradation of acetaminophen. The participation of different reactive species during the photocatalytic degradation of ATP was determined. Experiments with scavenger agents indicate that the photogenerated holes are the predominant oxidizing reactive species. These results highlight the potential of g-C3N4 modified with SiO2 nanospheres as an efficient photocatalyst for the degradation of emerging contaminants, thus advancing sustainable water treatment technologies.

Catalysts doi: 10.3390/catal16070592

Authors: Nadiah Y. Aldaleeli Taymour A. Hamdalla Saleh A. Alghamdi Shahid Alfadhli Nourhane A. Darwich Mahmoud I. Khalil Meshari M. Aljohani

Nanoparticles have attracted considerable interest for biomedical and catalytic applications due to their unique functional properties. This study aims to evaluate the structural, optical, photoelectric, photocatalytic, and wound-healing performance of cetyltrimethylammonium bromide (CTAB) and cellulose nanoparticles with complementary physicochemical characteristics. The nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Ultraviolet–Visible (UV–Vis) spectroscopy, while photoelectric properties were assessed through current–voltage (I–V) measurements. Photocatalytic activity was evaluated using methylene blue degradation under solar irradiation, and in vivo wound healing was examined using a rat excisional model over 13 days. Cellulose nanoparticles exhibited nearly double the photocurrent compared to CTAB, indicating enhanced charge transport efficiency. Photocatalytic results showed that cellulose achieved approximately ~70% degradation within 210 s, compared to ~50% for CTAB. In vivo findings revealed that cellulose achieved 82% wound closure, compared with 71% for CTAB, 67% for Betadine, and 35% for untreated controls, accompanied by improved tissue regeneration. Overall, cellulose nanoparticles exhibited better photoelectrochemical, photocatalytic, and wound-healing properties, whereas CTAB provided structural integrity and antimicrobial properties. These materials are therefore promising multifunctional nanomaterials for catalytic and biological applications.

Catalysts doi: 10.3390/catal16070590

Authors: Yabo Wang Tao Meng Dongsen Mao Qiangsheng Guo Jun Yu

In this study, a series of CuaZnbOx catalysts with tunable Cu/Zn molar ratios were fabricated via a MOF-on-MOF precursor strategy for CO2 hydrogenation to methanol. The optimal catalyst, Cu6Zn4Ox, achieved a CO2 conversion of 14.4%, a methanol selectivity of 81.1%, and a space-time yield of 902.1 gMeOH·kgcat−1·h−1 at 280 °C and 3 MPa with a GHSV of 24,000 mL·gcat−1·h−1. Characterization results revealed that this strategy successfully constructed small-sized Cu and ZnO particles as well as abundant Cu–ZnO interfaces, reaching the optimal structural and compositional state when the Cu/Zn molar ratio is tuned to 6:4. The effective Cu–ZnO interface on Cu6Zn4Ox promotes the CO2 adsorption and H2 dissociation, triggering the formation of carbonate species and resulting in the generation of methanol via a carbonate–formate pathway. This work provides a new insight for the rational design of high-performance CO2 hydrogenation catalysts through precursor interface engineering.

Catalysts doi: 10.3390/catal16070591

Authors: Surove Rani Saha Nure Alam Siddique Mostafizur Rahaman Merajuddin Khan Nayan Ranjan Singha Afzal Khan Mohammad Imran Hossain Mohammad A. Hasnat

Due to the scarcity and high cost of precious metals, development of a noble metal-free, low-cost catalyst for hydrogen generation via water splitting is crucial. To develop an efficient HER catalyst, Ti, the ninth most abundant metal in Earth’s crust, was engineered systematically. The pristine transition metal titanium cannot drive an electrocatalytic hydrogen evolution reaction (HER) with an efficient rate in an acidic medium (0.5 M H2SO4). However, in situ growth of TiO2 film on Ti surface achieves HER activity, showing an overpotential for 10 mAcm−2 at 671.4 mV with a Tafel slope of 163.69 mV dec−1. The electrocatalytic performance was further boosted by immobilizing CuO particles onto the as-developed TiO2/Ti film, which shows 10 mA cm−2 overpotential at 543.7 mV with a Tafel slope of 101.09 mV dec−1. The CuO–TiO2/Ti heterostructured electrode exhibited remarkable long-term stability, with the current density increasing by 36% over 25 h of continuous operation, suggesting gradual electrochemical activation while maintaining robust catalytic performance. In this research, detailed structural, surface, and electrochemical investigations, including SEM–EDX, EIS, OCP, and XPS analyses, verified the optimized formation of the TiO2 layer and CuO incorporation, underscoring the positive impact of heterointerface engineering on HER enhancement.

Catalysts doi: 10.3390/catal16070589

Authors: Beatrice Musig María Aznar María Elena Gálvez María Victoria Navarro

The great impact of carbon dioxide emissions on climate change motivates the development of technologies for carbon capture and utilization. CO2 methanation, which transforms CO2 into methane using renewable hydrogen, is a promising power-to-gas and carbon utilization pathway. Achieving high activity, strong CH4 selectivity, and long-term stability remains challenging, as well as pushes to tailor catalyst properties for the methanation reaction. Cerium oxide is therefore widely explored as a support or promoter due to its redox behaviour and oxygen vacancy chemistry. This review surveys recent literature on catalysts based and containing CeO2 applied for CO2 methanation, covering not only thermal operation but also non-conventional catalytic routes as photothermal, electrocatalytic, and plasma-assisted, with emphasis on how synthesis and role of Ce tune physicochemical properties and catalytic activity. Across reported systems, dispersing active metals (notably Ni and Ru, Cu for electrochemical systems) on ceria frequently yields to high CH4 selectivity. Redox properties of ceria enable optimal metal–support interactions and surface basicity to achieve effective CO2 activation in thermo-catalytic route. Further enhancement of oxygen mobility is associated with doped CeO2 and solid solutions such as Ce-Zr. The high oxygen storage capacity of CeO2 promotes photogenerated charge separation for light-driven performance and optimal plasma–catalyst interactions.

Catalysts doi: 10.3390/catal16070588

Authors: Nicolás A. Sacco Victoria Salinas Constanza Pierantoni Emerson Burna Fernanda Miranda Zoppas Fernanda Albana Marchesini

Copper-based catalysts supported on γ-Al2O3 were prepared by wet impregnation and evaluated for the catalytic wet peroxide oxidation (CWPO) of phenol. Citric acid was used as a complexing agent to enhance copper stabilization, and lanthanum was incorporated as a structural promoter. The effects of calcination temperature, heating rate, Cu loading, and La incorporation route on catalyst structure and performance were systematically investigated. Thermal treatment and La incorporation-controlled phase evolution and copper oxidation state. Calcination at 900 °C promoted the development of CuAl2O4- and CuAlO2-type phases, as suggested by XRD, while XPS showed that the Cu2+/Cu+ ratio increased progressively with temperature, consistent with stronger metal–support interactions. Citric acid, incorporated at a CA:Cu molar ratio of 1:1, reduced copper leaching by up to 50% compared to catalysts prepared without the complexing agent, regardless of calcination temperature. Co-impregnated Cu–La catalysts achieved complete phenol conversion within 20–30 min and TOC removals of 84–95%, depending on synthesis conditions. The combination of La incorporation, calcination at 900 °C, and citric acid-assisted impregnation yielded the best stability–activity balance, with Cu5.0/La-A-900-1 showing 91% TOC removal and only 18% Cu leaching after 2 h of reaction. XPS, catalytic performance, and leaching results indicate that CWPO activity is governed by the balance between redox accessibility (Cu2+/Cu+) and structural stabilization of copper species. The results indicate that CWPO proceeds through a combined surface-mediated and homogeneous Fenton-like pathway, where the relative contribution of each depends on copper stabilization and leaching.

Catalysts doi: 10.3390/catal16070587

Authors: Chien Thang Doan Thi Hang Phuong Thi Thanh Nguyen Thi Ngoc Tran San-Lang Wang

Jackfruit seeds, a by-product of the jackfruit processing industry, comprise a substantial proportion of starch. As a result, jackfruit seeds are emerging as a viable source of fermentable sugars for fermentation processes. In this study, α-amylase from Bacillus licheniformis TKU004 was employed to hydrolyze gelatinized jackfruit seed starch slurry, and the hydrolysis conditions were systematically optimized using the Box–Behnken design (BBD) coupled with response surface methodology (RSM). Three independent variables, including incubation temperature (40–60 °C), enzyme-to-substrate ([E]/[S]) ratio (5–10 U/g), and reaction time (2–6 h), were evaluated, with dextrose equivalent (DE, %) as the response. The optimal hydrolysis parameters were determined to be 47 °C, an [E]/[S] ratio of 10 U/g, and a reaction time of 5.1 h, yielding a predicted DE of 31.72%. Experimental validation confirmed a DE of 32.85 ± 1.12%, in close agreement with the model prediction. HPLC (high-performance liquid chromatography) analysis of the hydrolysate revealed a composition of 14.20% glucose, 56.51% maltose, and 29.29% maltooligosaccharides, indicating that this process is well-suited for producing high-maltose syrup. In short, this study demonstrates the feasibility of valorizing jackfruit seed waste into value-added carbohydrate products through enzymatic hydrolysis with B. licheniformis α-amylase.

Catalysts doi: 10.3390/catal16070586

Authors: S. N. Osmanova E. H. Ismailov A. I. Rustamova Y. A. Abdulazimova G. F. Mammadova L. V. Huseynova L. Kh. Qasimova Sh. F. Tagiyeva M. Vorochta J. W. Thybaut

A working-state model is proposed for the MnOx–Na2WO4/SiO2 catalyst in oxidative coupling of methane (OCM), where a Na2WO4-rich surface environment forms an adaptive interphase that buffers the effective interfacial oxygen chemical potential and stabilizes cooperative MnOx/Na–WOx/Mn–O–W motifs. A thermodynamic-kinetic scheme is developed that relates (1) reaction-induced surface enrichment (structural stabilization), (2) oxygen spillover (damping of local oxygen gradients), and (3) Mn ↔ W redox exchange as an electron-oxygen buffer channel. Ex situ XPS/EDS/EPR data indicate a dynamically stratified near-surface region with chemically heterogeneous environments of Mn, W, and O. The W 4f region remains dominated by the W6+ contribution in the presence of a minor reduced component after OCM. In oxygen-deficient mixtures (CH4/O2 > 4), interfacial reconstruction becomes more pronounced: Mn-centered Mars–van Krevelen chemistry determines CH4 activation and oxygen exchange, while the Na2WO4-rich phase ensures fast ion/oxygen transport. Observation of the EPR signal from W5+ ions in the tungstate matrix indicates the existence of reduced W intermediates at low oxygen potential. Optimization of C2 selectivity and stability is suggested to require maintaining the catalyst within the selective window of effective interfacial μO by adjusting CH2/O2 and contact time, as well as controlling the architecture of the Na–W–O/MnOx interfacial region.

Catalysts doi: 10.3390/catal16070585

Authors: Anchal Rawat Navneet Kaur Chirag G. Makvana Harvinder Singh Sohal Manvinder Kaur Ankush Mehta Ketankumar A Ganure Mohd Rafatullah

The discharge of dye-loaded textile effluents poses serious environmental concerns due to their high stability. In this study, a magnetic Fe2O3/TiO2/NBC (FNT) heterostructure, derived from Cannabis sativa-based nanobiochar (NBC), was developed for crystal violet (CrV) degradation via peroxymonosulfate (PMS) activation. The crystalline structure, surface functional groups, morphology, and elemental composition were analyzed using advanced characterized of the synthesized catalyst. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of Fe3+, Ti4+, and abundant surface oxygen species. Under UV light, efficient electron transfer across the FNT interface promoted PMS decomposition into hydroxyl and sulphate radicals. Electrochemical results indicated reduced charge recombination and enhanced electron mobility. Under optimal conditions (PMS = 75 mg/L, FNT = 30 mg/L, pH 7), 98.9% CrV degradation was achieved within 120 min. The catalyst maintained over 97% efficiency after five cycles, demonstrating excellent stability and reusability. Overall, this research demonstrates a robust and sustainable catalytic system for efficient dye degradation, offering strong potential for practical wastewater treatment applications.

Catalysts doi: 10.3390/catal16070584

Authors: Jingling Pei Qingli Shu Wenwen Zhang Qi Zhang

Ammonia-selective catalytic oxidation (NH3-SCO) is an effective technology for eliminating NH3 slip; however, the development of catalysts that simultaneously exhibit excellent low-temperature (<350 °C) activity and high N2 selectivity remains a significant challenge. A novel structured monolithic mesh-type Fex-Mn2O3/γ-Al2O3/Al catalyst was developed. XPS, H2-TPR, and O2-TPD results demonstrate that Fe doping markedly increases the concentration of surface-adsorbed active oxygen species and enhances the redox capability. As a result, the optimally doped Fe6.61-Mn2O3/γ-Al2O3/Al catalyst achieved complete NH3 conversion at 210 °C with a 75% N2 selectivity, outperforming previously reported Mn-based catalysts. Density functional theory (DFT) calculations further confirm that Fe modification enhances O2 adsorption energy. In addition, the introduction of Fe significantly improves the catalyst’s resistance to SO2 and H2O. In situ FTIR results indicate that the NH3-SCO reaction over Fe-Mn2O3/γ-Al2O3/Al proceeds predominantly via an internal selective catalytic reduction (i-SCR) pathway.

Catalysts doi: 10.3390/catal16070583

Authors: Mingzi Sun Wenzhuo Liu Yun Li Jilin Cao

Developing high-performance non-precious metal catalysts for the methanol oxidation reaction remains a challenge for direct methanol fuel cells. Herein, a nickel-doped Beta (Ni-Beta) zeolite was successfully synthesized via a template-free one-pot hydrothermal route followed by protonation via ammonium exchange. In this work, the protonation process strengthened metal–support interaction to form Ni2+/Ni3+ redox pairs, introduced abundant acidic sites, and optimized the zeolitic pore structure. Optimized Ni-H-Beta-170 (Si/Ni = 170) achieved a remarkable mass activity of 71.6 A g−1 at 0.66 V vs. Hg/HgO, around 10-fold higher than unprotonated Ni-Beta zeolite. The improved activity originates from reversible Ni2+/Ni3+ cycles for eliminating toxic COads, enriched acid sites accelerating C–H cleavage of methanol and formation of active NiOOH, and enlarged pore volume facilitating mass transfer. This work offers a low-cost strategy toward advanced non-precious methanol oxidation reaction electrocatalysts.

Catalysts doi: 10.3390/catal16070582

Authors: Ghania Abid Zoubir Benmaamar Houcine Boutoumi Tarek H. Taha Hamdi Bendif Lotfi Mouni

The contamination of aquatic ecosystems by synthetic dyes such as Safranin O poses significant environmental and health risks. This study reports the synthesis of TiO2-ZnO heterostructures via a Ruta graveolens-mediated sol–gel method, where the plant extract acts as a structure-directing agent and precursor for residual carbon species. The resulting bio-hybrid catalyst achieved a degradation efficiency of 94% ± 2% under simulated solar irradiation, outperforming UV light (78% ± 3%) and visible light alone (81.18%). The optimal catalyst loading was determined to be 1.0 g L−1, with maximum performance observed at near-neutral pH (6–7). Optical characterization revealed a direct bandgap of 2.69 eV, representing a significant red-shift from pristine TiO2 and ZnO. The catalyst maintained 90% of its initial degradation efficiency after five consecutive regeneration cycles, demonstrating excellent reusability. Kinetic analysis confirmed pseudo-first-order behavior, while radical scavenging experiments identified superoxide radicals (•O2−) as the dominant reactive species. This work establishes that plant-derived carbon precursors can effectively modify the electronic properties of TiO2-ZnO heterojunctions, offering a sustainable approach for photocatalytic water remediation.

Catalysts doi: 10.3390/catal16070581

Authors: Yu-Cheng Shih Ren-Jang Wu Mohammod Hafizur Rahman Sayeed Rushd Ammar Fayez Al-Shayeb Md Arifuzzaman

Formaldehyde (HCHO), a prevalent indoor air pollutant released from furniture and building materials, poses significant health risks due to its carcinogenic nature. In this study, a binary cuprous oxide–titanium dioxide (Cu2O–TiO2) composite photocatalyst was synthesized via a hydrothermal method to enable efficient visible-light-driven degradation of gaseous formaldehyde at ambient temperature. The structural, morphological, and optical properties of the as-prepared catalysts were characterized using XRD, SEM, TEM, EDX, and UV-Vis spectroscopy. While pristine Cu2O exhibited a formaldehyde degradation efficiency of approximately 68% under white light illumination, the incorporation of TiO2 markedly enhanced the photocatalytic performance. Among the different mass ratios tested, the Cu2O–TiO2 (1:1) composite demonstrated the highest activity, achieving 83% degradation of formaldehyde within 240 min under white light. Enhanced performance is attributed to the formation of a heterojunction that reduces the effective bandgap, promotes charge separation, and suppresses electron–hole recombination. Additionally, the generation of carbon dioxide and water as end products confirmed complete mineralization. The catalyst also showed good reusability, retaining over 81% efficiency after five cycles. This work presents a cost-effective, stable, and visible-light-active Cu2O–TiO2 heterojunction photocatalyst with strong potential for indoor air purification applications.

Catalysts doi: 10.3390/catal16070580

Authors: Norbert Graefe Jonas Gunkel Christian Sonnendecker Wolfgang Zimmermann Georg Künze

Polyethylene terephthalate (PET) is one of the most widely used plastics for single-use applications, with annual global production exceeding 80 Mt. Enzymatic degradation of PET has emerged as a promising and sustainable alternative to conventional recycling methods, enabling the hydrolysis of PET into its constituent monomers. While amorphous PET can be efficiently degraded by polyester hydrolases identified from environmental sources, crystalline PET remains highly recalcitrant to enzymatic attack and constitutes a major bottleneck for the industrial implementation of enzymatic PET recycling. Although physicochemical pretreatments can increase PET amorphicity, these approaches often require substantial energy input, thereby compromising the overall sustainability of the process. Consequently, the development of enzymes capable of directly degrading crystalline PET has long been sought; however, currently engineered enzymes exhibit insufficient catalytic activity toward highly crystalline PET owing to multiple factors, including limited substrate surface accessibility, highly ordered polymer morphology, incompatible binding-pocket geometries, restricted chain mobility, and unfavorable conformational energetics at the polymer–enzyme interface. This review aims to evaluate the factors limiting the enzymatic degradation of crystalline PET and to assess current strategies for overcoming low degradation rates. Specifically, it examines advances in substrate modification as well as enzyme- and process-engineering approaches designed to improve the depolymerization of crystalline PET. The advantages and limitations of these strategies are critically compared and discussed, highlighting the remaining challenges and future directions toward efficient and scalable biocatalytic PET recycling.

Catalysts doi: 10.3390/catal16070579

Authors: Mencui Ning Runhu Zhang

Fe-ZSM5 zeolite materials were prepared via solid-state ion exchange and comprehensively characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The XRD patterns confirm the successful loading of iron species onto the ZSM-5 support. These materials served as heterogeneous Fenton catalysts for the degradation of methyl orange in simulated wastewater. Key operational parameters—including initial pH, H2O2 concentration, catalyst dosage, and reaction temperature—were systematically evaluated to assess their effects on decolorization efficiency. The results indicated that under optimal conditions (initial pH of 3.0, H2O2 concentration of 0.3 mol/L, catalyst dosage of 1.6 g/L, reaction temperature of 30 °C), a decolorization efficiency of 92.58% was achieved within 60 min. This study demonstrates that Fe-ZSM5 zeolite is a robust and efficient catalyst for heterogeneous Fenton-based degradation of organic dyes in aqueous systems.

Catalysts doi: 10.3390/catal16070578

Authors: Jingpeng Gan Peng Chen Wei Xia Xinrui Wang Mingyuan Dong Zhenhua Jiang Yanli Zhang Di Wang Kun Chen Dong Liu

CO2 methanation with renewable hydrogen is a promising strategy for carbon valorization and synthetic natural gas (SNG) production. However, the molecular mechanisms behind catalyst-dependent adsorption and mass transport in zeolite-confined spaces are still not fully elucidated. Herein, we performed comparative molecular simulations on HZSM-5, Ni/ZSM-5 and Ru/ZSM-5 by combining density functional theory (DFT), grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) methods, aiming to clarify the thermodynamic and mass transport mechanisms of reactant enrichment and product desorption in CO2 methanation. The electronic structures of the three systems were systematically evaluated via Mulliken charge analysis, differential charge density mapping, and frontier molecular orbital calculations. We further quantified the adsorption thermodynamics and diffusion kinetics of reactants and products, focusing specifically on the effects of temperature and framework Si/Al ratio for Ni/ZSM-5. The results show that Ni doping greatly modulates the local electronic environment of the ZSM-5 framework, enhancing the adsorption of CO2 (−121.9 kJ·mol−1) and H2 (−81.6 kJ·mol−1) and weakening the adsorption of CH4 and H2O. A higher Si/Al ratio reduces CO2 adsorption capacity, while elevated temperatures inhibit reactant adsorption and lower the diffusion selectivity of CH4. This demonstrates that moderately low temperatures and moderate Si/Al ratios can optimize the adsorption and diffusion behaviors of reactants and products. This work provides molecular-level insights into the adsorption and diffusion behaviors of Ni/ZSM-5 and offers theoretical references for the rational development of high-performance CO2 methanation catalysts.

Catalysts doi: 10.3390/catal16070577

Authors: Yumei Li Da Han Na Li Zhengbing Fu De Fang Junlin Xie

The practical application of Li–O2 batteries is severely hindered by parasitic reactions on the cathode side, which generally lead to large charging over-potentials and degraded cyclic performance. To address this issue, it is essential to integrate high-efficiency catalysts into conventional carbon-based electrodes. Herein, we report a novel La0.85Ca0.15Cr0.85O3@Ru (LCC@R) hybrid catalyst with an ultralow Ru loading (6.55 wt.%), synthesized via a facile sol-gel combined with in-situ reduction-exsolution method. Mono-dispersed and ultrafine Ru nanocrystals (2–5 nm) are uniformly anchored on the LCC substrate and serve as the catalytically active sites. The Li–O2 battery with the LCC@R catalyst exhibits a low charge potential of 3.75 V at a current density of 50 mAg−1 with limited capacity of 500 mAhg−1. Impressive cyclic stabilities of up to 80 cycles (at 1000 mAhg−1) and 15 cycles (at 2000 mAhg−1) are achieved. Moreover, a large specific capacity of 8630 mAhg−1 is delivered at 50 mAg−1. Mechanistic studies reveal that the intermediate discharge product LiO2 can be absorbed on LCC@R, thereby inhibiting the parasitic reactions induced by LiO2 attack on carbon. The as-prepared LCC@R hybrid material is a promising cathode catalyst for constructing long-cycle-life and low-over-potential Li–O2 batteries.

Catalysts doi: 10.3390/catal16070576

Authors: Lu Wang Chao Yu Yiwa Wang Xiuming Liu Jingnan Li Lili Ma Jiamei Wei Zerun Zhao Wanru Feng Zhanggui Hou Songbao Fu

Incorporating comonomers in propylene polymerization plays a critical role in tuning the physical and chemical properties of the resulting polymers. In this study, the impact of three developed comonomers on propylene polymerization over the triethylaluminum-treated TiCl3 catalyst was investigated in detail by DFT. The results indicate that these comonomers remain highly stable under actual catalytic conditions, with their ions or functional groups showing a low propensity for detachment, which would otherwise poison the catalyst or disrupt the polymerization process. However, the three comonomers on the surface with a strong adsorption capacity may compete with propylene for adsorption, which will affect the polymerization. Among them, Vinyltrimethoxysilane, which exhibits the strongest adsorption ability, tends to form bonds with the ethyl on the catalyst surface, leading to catalyst poisoning and inhibiting the reaction. In contrast, 5-hexenyl methyldichlorosilane demonstrates relatively higher activity due to its balanced properties. The order of reactivity in the polymerization reaction: 5-hexenyl methyldichlorosilane > 5-hexenyldichlorophosphonane > vinyltrimethoxysilane. This work provides fundamental mechanistic insights into how functional comonomers interact with catalytic active sites through adsorption, competitive reactions, and insertion processes. Additional free energy analysis at 333 K confirms that these mechanistic trends remain unchanged under realistic reaction conditions. Rather than directly simulating industrial catalysts, the present study focuses on a model TiCl3 system to elucidate intrinsic structure-reactivity relationships. These findings contribute to a deeper understanding of comonomer effects in olefin polymerization at the molecular level.

Catalysts doi: 10.3390/catal16070575

Authors: C. K. Zagal Padilla Angelica Julieta Alvillo-Rivera Rocío Nava Virginia Gómez-Vidales R. Suárez-Parra Sergio A. Gamboa J. Zamora H. Martínez

A biogenic ZnO/Ag photoelectrode treated with atmospheric-pressure plasma was evaluated as an anode in a photo-assisted electroflotation system for the transformation of chromophoric pollutants in real industrial wastewater. ZnO was synthesized from Azadirachta indica leaf extract and plasma-treated for 10 min (M2) and 15 min (M3), with an untreated reference (M1). XRD, SEM-EDS, Raman, FTIR, EPR, and XPS analyses showed that the plasma preserved the wurtzite structure, relaxed the bulk, and modified the surface by removing residues, deoxygenating it, and activating oxygen vacancies (VO). Although M3 reached the highest deoxygenation, M2 showed the most favorable response; thus, the performance did not depend only on the total amount of VO. Under dark conditions, M2 showed a 14.86 percent decrease in COD compared to the control in a single batch and had the most negative ORP value. However, only ORP came close to statistical significance after multiplicity correction, with padj = 0.055. Under illumination, it showed the strongest photoinduced changes in conductivity and total suspended solids. The light–dark differences (ΔL−O) showed sign reversals in COD, conductivity, and pH, which identified three functional regimes and indicated that the electronic coupling of the surface VO, rather than its amount, controlled the performance. ΔL−O was proposed as an operational test to distinguish these regimes, with the plasma exposure time as a key control variable. Because the effluent responses were single determinations, they are considered exploratory; the mechanism is primarily based on structural and spectroscopic characterization and supported by photoelectrochemical tests.

Catalysts doi: 10.3390/catal16070574

Authors: Xinyi Yang Xindi Feng Jiongyi Chen Youcai Zhu Zhen Liu

This work investigates a novel GaCl3·AlCl3/H2O catalytic system for the synthesis of low-molecular weight polyisobutylene (LPIB). Catalytic performance was improved by employing a dual Lewis acid system, which outperformed the conventional single component (GaCl3/H2O) catalyst in terms of both reaction rate and yield. In accordance with the optimized reaction conditions, the conversion of monomer was found to be 97%, thereby achieving low molecular weight polyisobutylene (LPIB) with a number average molecular weight (Mn) of 3900 g/mol. Density functional theory (DFT) calculations revealed a lower proton transfer barrier (5.8 kcal/mol) in the dual Lewis acid catalytic structure compared to its single component counterpart. Subsequent theoretical analyses, incorporating electrostatic potential (ESP), independent gradient model based on Hirshfeld partition (IGMH), and distortion/interaction analysis, attributed this observed kinetic advantage to a higher positive ESP extremum and enhanced interaction between the IB fragment and the Lewis-acidic active center. Together, these results establish the GaCl3·AlCl3/H2O dual Lewis acid system as an enhanced catalytic platform over the conventional GaCl3/H2O system for efficient IB polymerization toward LPIB synthesis.

Catalysts doi: 10.3390/catal16060573

Authors: Fu-Lung Lin Che-Ju Tseng Ko-Shan Ho

Developing cost-effective alternatives to platinum-based catalysts remains paramount for commercializing anion exchange membrane fuel cells (AEMFCs). We report a metal-free nitrogen-doped carbon catalyst derived from a rationally designed polyurea–polyimine copolymer that outperforms commercial 20 wt% Pt/C in superior relative durability and methanol tolerance. Strategic integration of polyurea’s pore-forming capability with polyimine’s thermal stability enabled the synthesis of a catalyst (NC-1000N) featuring ultrahigh surface area (1276.5 m2 g−1), optimal nitrogen speciation (20.5% pyridinic-N, 45.3% graphitic-N), and enhanced graphitization, which improves the electrical conductivity of catalysts. NC-1000N exhibited exceptional oxygen reduction performance with an onset potential of 0.96 V, almost four-electron selectivity (n = 3.87), a medium Tafel slope (105 mV dec−1), and minimal charge transfer resistance (46.74 Ω). When evaluated in single-cell AEMFCs, NC-1000N delivered a peak power density of 372.1 mW cm−2, which is 26% higher than Pt/C at equivalent loading, while demonstrating superior stability (94.8% retention after 7 h) and complete methanol tolerance. Systematic pyrolysis temperature optimization (800–1000 °C) revealed critical structure–property relationships governing catalyst evolution from disordered precursor to highly graphitic, nitrogen-enriched carbon with precisely engineered active sites. This work establishes polymer-derived carbons and provides design principles for scalable synthesis of high-performance metal-free electrocatalysts for sustainable energy conversion technologies.

Catalysts doi: 10.3390/catal16060572

Authors: Eda Mehtap Özden Hatice Kızıltaş İlhami Gulcin

Coniferyl alcohol and coniferyl aldehyde are precursors of lignin and are used in spices and the pharmaceutical industry. In this work, antioxidant, anticholinergic, antidiabetic, and antiglaucoma effects of coniferyl alcohol and aldehyde were evaluated and compared against the standards. To determine the antioxidant capacities of coniferyl alcohol and aldehyde, ABTS•+, DMPD•+ and DPPH• scavenging abilities as well as cupric ion (Cu2+) reduction, ferrous ions (Fe2+) reduction and Fe3+-TPTZ reduction activities were studied. Butylated hydroxytoluene (BHT), ascorbic acid, α-Tocopherol, Trolox, and butylated hydroxyanisole (BHA) were used as the standard antioxidants. When the antioxidant effects of coniferyl alcohol and coniferyl aldehyde are compared to the standards, they exhibit significant antioxidant effects. In addition, it was determined that coniferyl alcohol and coniferyl aldehyde had a high degree of inhibition effect towards carbonic anhydrase (hCA) I and II isoforms purified from human erythrocytes, α-glycosidase, butyrylcholinesterase (BChE), acetylcholinesterase (AChE), and α-amylase as in vitro and in silico. Molecular docking studies revealed favorable binding affinities of coniferyl alcohol and coniferyl aldehyde toward all investigated enzymes, with key hydrogen bonding and π–π interactions identified at the active sites. The docking findings were found to be compatible with the in vitro enzyme inhibition results, supporting the proposed multi-target biological potential of both compounds. Molecular docking studies revealed favorable binding affinities of coniferyl alcohol and coniferyl aldehyde toward all investigated enzymes. Key hydrogen bonding and π–π interactions were identified within the active sites, particularly for AChE and hCA II. The docking results were consistent with the in vitro enzyme inhibition data, supporting their multi-target biological potential. Docking demonstrated that both compounds can effectively interact with the catalytic regions of the target enzymes. The identified binding modes and interaction patterns support the observed inhibitory activities and provide a molecular basis for their multi-target biological effects.

Catalysts doi: 10.3390/catal16060570

Authors: Catalina Astudillo Dana Arias Gina Pecchi Catherine Sepúlveda Jorge N. Díaz de León Carla Herrera

The influence of carbon support and Cu loading on the structural, surface, and catalytic properties of Cu-based catalysts for furfural hydrogenation was systematically investigated. Two activated carbons with distinct textural and chemical characteristics were evaluated: a biomass-derived carbon (ACS) and commercial carbon (ACC). The ACC support exhibited a higher density of thermally stable oxygen-containing functional groups, which promoted stronger metal-support interactions and an increased proportion of surface reduced Cu species (Cu0/Cu+), resulting in superior catalytic performance compared to ACS. Based on these results, the effect of Cu loading (5–20 wt.%) was further studied on the ACC support. The catalysts were characterized by N2 physisorption, XRD, TEM, H2-TPR, He-TPD, NH3-TPD, and XPS. Increasing Cu loading enhanced the amount and reducibility of Cu species; however, excessive loading led to particle growth, pore blockage, and reduced metal dispersion. Catalytic activity exhibited volcano-type behavior, reaching a maximum at 15 wt.% Cu, where an optimal balance between reduced availability of Cu species and metal-support interaction was achieved. Selectivity toward furfuryl alcohol remained essentially unchanged across all catalysts, indicating that the catalytic performance is closely related to the surface chemistry and relative concentration of reduced Cu sites and is not significantly affected by acidity. These results highlight the critical role of support properties and metal loading in controlling catalyst performance, providing insights for the rational design of efficient Cu-based catalysts for biomass valorization.

Catalysts doi: 10.3390/catal16060571

Authors: Ziyun Zhang Lisi Yuan Liwenze He Shike Liu Min Zhou Zhihang Xiong Dengpeng Song

The rational design of metal-free catalysts capable of efficiently converting CO2 under atmospheric pressure remains a significant challenge in sustainable chemistry. Herein, we report a series of clamp-shaped dihydrogen-bonded iodide catalysts (CDBI catalysts) featuring a preorganized bifunctional framework that integrates dual hydrogen-bond donors and an intrinsic iodide nucleophile within a single molecular scaffold. Systematic structural variation revealed that catalytic activity is highly sensitive to electronic modulation, steric accessibility, and precise spatial arrangement between the hydrogen-bonding units and the iodide center. The optimal catalyst enabled solvent-free cycloaddition of CO2 with epoxides at 1 atm CO2, affording up to 99% conversion and >99% selectivity at 80 °C within 12 h. Substrate scope studies demonstrated efficient transformation of a wide range of terminal epoxides, while sterically demanding substrates exhibited reduced reactivity consistent with a confined activation mode. Mechanistic investigations support a cooperative pathway in which dual hydrogen-bond activation and proximal halide nucleophilicity operate synergistically within a preorganized clamp-shaped pocket. Comparative analysis with representative catalytic systems highlights the ability of this metal-free design to achieve high efficiency under atmospheric CO2 without cocatalysts or solvents. These findings demonstrate that structural preorganization represents an effective strategy for promoting sustainable CO2 utilization under operationally simple conditions.

Catalysts doi: 10.3390/catal16060569

Authors: Saeed Vohra Varun Chauhan Mohsin Khan Nadeem Raza Anis Ahmad Chaudhary

Demand for greener and safer chemistries has driven the innovation of bioinspired and enzyme-mimicking catalysts for selective and efficient oxidation and hydrogenation under mild conditions. Natural catalysts, including peroxidases, oxidases, hydrogenases, oxygenases and dehydrogenases, boast remarkable activity, specificity, stability, selectivity, low energy requirements and atom economy. Disadvantages of enzymes, such as poor thermal stability, a narrow operational range, low recovery yield and the expense of purification, are motivating the discovery and design of enzyme substitutes. Several artificial platforms have appeared recently: nanozymes, artificial metalloenzymes, biomimetic metal Complexes, MOFs, atomic catalysts, bioinorganic hybrid systems, among others. These systems aim to replicate key structural and mechanistic features of enzymes while providing greater operational stability, recyclability, and scalability. Recent work has demonstrated the benefit of enzyme mimics in increasing eco-sustainability in reactions such as alcohol oxidation, selective alkane oxidation, waste degradation, catalytic photooxygen activation and biomass waste conversion. Similarly, biomimetic hydrogenation catalysts have shown outstanding activity in asymmetrically hydrogenating chemicals, reducing CO2 into chemicals, hydrogenation by hydrogen transfer and creating hydrogen through water. Through control of active sites, second coordination sites, defects and electrons/protons in the system, significant gains have been seen in reaction selectivity and frequency of turning over substrate into product. Nanozymes, biohybrid catalysis and artificial catalysts guided by deep learning are further broadening the applications of biomimetic catalysis in oxidation and hydrogenation. The article review aims to provide a summary of the most current progress with bioinspired and enzyme-mimicking catalysts, focusing on catalytic mechanisms, how to design such catalysts, how green chemistry benefits from their development and where further application is likely in the coming years.

Catalysts doi: 10.3390/catal16060568

Authors: Zuzeng Qin

Over the past few decades, the advancement of human society and industrialization has led to severe environmental issues, such as air and water pollution, greenhouse effects, and climate change [...]

Catalysts doi: 10.3390/catal16060567

Authors: Musarat Shahin Abdul Haseeb Mohsin Aiman Bibi Ihtisham Ahmad Elif Esra Altuner Ozan Aldemir Senol Durmusoglu Mehmet Sabit Yilancilar Yavuz Tanriverdi Esra Acar Busra Akinalan Balik Ghassan Issa Muzaffer Elmas Veli Cengiz Ozalp

Substantial advances have been made since the 1970s in reducing the environmental impacts of ammonia production. Renewable-driven electrochemical synthesis offers a promising pathway to decarbonize ammonia production. This review examines an integrated route in which hydrogen is generated photoelectrochemically under concentrated solar irradiation and subsequently used in electrochemical ammonia synthesis. Photoelectrochemical cells are fabricated by electrostatically depositing photosensitive particles onto cathodes to enhance light-driven hydrogen production. Hydrogen production rates and ammonia yield depend strongly on temperature and electrolyte composition. The synthesized hydrogen is fed into a molten salt electrochemical reactor that operates at atmospheric pressure and receives nitrogen from a dedicated supply. This combined solar–electrochemical approach can produce low-carbon ammonia with improved safety and reduced environmental impact, offering a scalable alternative to conventional processes.

Catalysts doi: 10.3390/catal16060566

Authors: Shuang Wang Wanying Yang Rui Zhong Meiling Zhao Fengfeng Li Yuxin Zhou Wenjuan Shan Xiujie Li

Ni-doped amorphous Al2O3 catalysts were successfully prepared for the one-step reduction of nitrobenzene to azoxybenzene using NaBH4 as hydrogen donors under mild conditions. The amorphous Ni1Al87Ox catalyst achieved a highly efficient azoxybenzene production rate of 1.89 mol·g-Ni−1·h−1, significantly outperforming its Ni/γ-Al2O3 counterpart. On the basis of the MAS NMR and XPS characterization results, the enhanced catalytic performance is associated with Ni incorporation during the preparation of amorphous Ni1Al87Ox, which introduces abundant unsaturated pentacoordinate Al species with oxygen vacancies and stabilizes Niδ+ sites against over-reduction. Notably, Ni1Al87Ox loaded on commercial ZSM-5 supports maintained an azoxybenzene yield of 9.02 mol·g-Ni−1·h−1, highlighting the strong potential for further scalable applications.

Catalysts doi: 10.3390/catal16060565

Authors: Guopei Zhang Cong Wang Xiaoyang Zhang Zhaomin Li Leteng Lin

Dry reforming of methane (DRM) enables the simultaneous conversion of CH4 and CO2, yet rapid coking severely restricts the stability of Ni-based catalysts. In this study, Co was incorporated into Ce-, La-, and Zr-promoted Ni catalysts to construct Ni-Co alloy active sites, and their catalytic behavior was systematically evaluated. While single-promoter modification partially suppressed coke deposition at the expense of activity, Ni-Co alloy formation maintained high reforming performance and significantly enhanced stable catalytic performance within the 20 h evaluation period, with the Ce-promoted Ni-Co catalyst exhibiting the most durable anti-coking performance. CO2-TPD and coke characterization results indicate that promoter species enhance medium-strength basicity and oxygen mobility, thereby facilitating CO2 adsorption and accelerating the oxidation of surface coke intermediates; in particular, Ce supplies mobile active oxygen species through its oxygen storage-release capacity. DFT calculations further reveal that Co incorporation modulates the electronic structure of Ni sites, optimizing the balance between CH4 dissociation and CO2 activation and thus suppressing excessive methane cracking. These findings elucidate the synergistic effect of Ni-Co alloying and promoter modification in DRM and provide mechanistic insight for the rational design of coke-resistant Ni-based catalysts.

Catalysts doi: 10.3390/catal16060564

Authors: Seetharamulu Podila Ahmad Alsobhi Majed A. Alamoudi Nagaraju Pasupulety

Ammonia decomposition over non-precious metal thermos-catalysts offers a viable and cost-effective pathway for sustainable hydrogen production. In this study, LaCeO3 perovskite was synthesized using a citric acid complexation method and employed as a support for mono- and bimetallic catalysts prepared by incipient wetness impregnation, maintaining a total metal loading of 10 wt%. Structural and surface properties were systematically investigated using BET, XRD, H2-TPR, SEM, TEM, and CO2-TPD. Among the monometallic catalysts (Ni, Co, and Fe), 10%Ni/LaCeO3 exhibited the highest activity, which is attributed to its enhanced reducibility and optimal surface basicity, facilitating NH3 activation. Bimetallic systems (Ni-Co, Ni-Fe, and Co-Fe) with equal metal loadings (5 wt% each) showed better activity compared to their monometallic counterparts following the order: 5%Ni–5%Co/LaCeO3 > 5%Ni–5%Fe/LaCeO3 > 5%Co–5%Fe/LaCeO3. The improved performance of the Ni-Co system is due to structural interactions between Ni and Co, which promote hydrogen desorption and accelerate N–H bond cleavage, while suppressing nitrogen recombination as the rate-limiting step. Further systematic optimization of the Ni/Co ratio showed that 8%Ni–2%Co/LaCeO3 had the highest catalytic activity with consistent performance over 50 h. This optimal composition provides a balanced distribution of active metallic sites and moderate-to-strong basic sites, enhancing NH3 adsorption and intermediate transformation. These findings show that LaCeO3-supported Ni-Co catalysts are promising candidates for efficient hydrogen production from ammonia without using noble metals.

Catalysts doi: 10.3390/catal16060562

Authors: Chaosheng Zhu Yonghong Zhang Lin Liu Zetong Yang Mingchen Sun Chao Fan Yongcai Zhang Juanjuan Liu

Traditional electro-Fenton systems for chlorinated antibiotic wastewater suffer from low mineralization, catalyst deactivation, and secondary pollution caused by chloride ions. In this work, nitrogen-functionalized graphite felt cathodes were synthesized by electrodeposition-pyrolysis. Pyridinic N and graphitic N were identified by XPS. The obtained cathodes were employed in a metal-free electro-Fenton system for effective tetracycline (TC) removal and mineralization. The results show that the optimal electrode (N-GF-3) achieved 93% degradation efficiency and 73% mineralization of TC in 60 min, when the optimized conditions (pH = 3 and current density = 20 mA/cm2) were employed. Unusually, with the presence of Cl−, the system showed even higher catalytic performance, having a degradation kinetic constant 2.4 times higher than that without chloride. The electrode was also reusable, maintaining a TC degradation efficiency above 90% in the fifth cycle. Based on fluorescence analysis of ·OH, a possible dual-path reaction mechanism is proposed. This mechanism provides new insights into designing advanced oxidation processes for the treatment of complex chlorinated organic wastewater. Nevertheless, the potential formation of chlorinated byproducts requires additional investigation.

Catalysts doi: 10.3390/catal16060563

Authors: Shuai Wang Peiyao Chen Wenqi Cui Yingning Wang Xiongwei Liang Yufeng Zhao Yang Yang

Tetracycline-class antibiotics are persistent contaminants in aquatic environments and are difficult to remove by conventional treatment processes. In this study, a recoverable granular MIL-101(Fe)/γ-Al2O3 catalyst was prepared through ligand anchoring followed by secondary Fe-MOF growth on spherical γ-Al2O3 and applied to catalytic ozonation of tetracycline (TC) under ordinary-bubble and microbubble-assisted operation. Structural characterization supported the formation of Fe-containing MOF domains on the alumina support, accompanied by an increase in BET surface area from 164.28 to 210.05 m2 g−1 and enhanced Lewis-acid-related pyridine-IR signals. Under conventional bubbling ozonation, the optimized catalyst achieved 67.93% apparent UV–Vis-based TC removal during an overall 50 min run consisting of 30 min dark adsorption followed by 20 min ozonation. In a 12 L microbubble reactor, the catalyst-assisted system reached 93.74% apparent UV–Vis-based TC removal at pH 6 with 100 g catalyst and 6 mg min−1 fed ozone, showing higher apparent removal than ordinary ozonation, microbubble ozonation, and ordinary-bubble catalytic ozonation under the tested configuration. Phosphate-blocking and radical-quenching experiments were consistent with the involvement of Lewis-acid-related sites, hydroxyl radicals, and superoxide-related pathways, but these tests are interpreted as indirect mechanistic evidence. LC-MS analysis suggested possible hydroxylation, demethylation, deamidation, ring opening, and low-molecular-weight product formation. The system also transformed chlortetracycline, oxytetracycline, and doxycycline and reduced COD and TOC in a simulated mixed-antibiotic matrix. Because parent-compound HPLC/LC-MS time-series quantification, ozone utilization/off-gas ozone measurement, bubble-size/kLa analysis, and ICP-based Fe loading/leaching data were not available, the present work is positioned as an apparent catalyst–reactor coupling study rather than a complete catalytic, hydrodynamic, or process-level demonstration.

Catalysts doi: 10.3390/catal16060561

Authors: Yanji Qian Haoyu Zhang Wenxi Han Wenxuan An Yizhu Wang Guangkun Yan Jing Xu Lianming Zhao

The sluggish kinetics of alkaline hydrogen oxidation reaction (HOR) and high cost of Pt–based catalysts have long hindered large–scale deployment of alkaline membrane fuel cells. Via first–principles calculations, we designed a series of 3d transition metal single atoms anchored on PdN2 monolayer (TM–PdN2, TM = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) and evaluated their alkaline HOR performance. Ti-, Cr-, Fe-, Co-, Ni-modified systems exhibit excellent thermodynamic and electrochemical stability under operating conditions. Single-atom doping tunes the p-band center of N and d-band center of metal sites, enabling precise modulation of H and OH adsorption strengths. Mechanistic analysis reveals HOR follows H2 + 2OH* → H* + OH* + H2O → 2H2O, with the final step as rate-determining step. H adsorption contributes 3.45 times more to HOR activity than OH adsorption. Fe–PdN2 delivers the best performance, with an ultra–low barrier of 0.11 eV and a rate constant of 2.82 × 1010 s–1·site−1, values that significantly outperform those of Pt(111) (0.22 eV, 4.5 × 109 s−1·site−1). This work provides theoretical guidance for rational design of high–performance alkaline HOR electrocatalysts.

Catalysts doi: 10.3390/catal16060560

Authors: Jinyi Lv Yidong Wang Hongyu Zhao Qingrong Li Jing Sun Yingping Pang Xinyan Zhang Tao Wang Yanpeng Mao Zhanlong Song Murodbek Safaraliev Xingxing Cheng Ziliang Wang

The utilization of biomass resources is of significant importance. However, the complexity of biomass thermochemical conversion processes and the performance limitations of conventional catalysts restrict the stable selection of reaction pathways and ultimately affect catalytic yields. With the rapid development of synthesis techniques and machine learning, nanoscale high-entropy alloys (HEAs) with targeted properties can now be accurately predicted and synthesized. The diverse compositions and structures of HEAs enable versatile catalytic selectivity, while their unique four core effects enhance catalytic activity and stability. This review primarily elaborates on the specific applications of HEAs in biomass thermochemical conversion. It covers the fundamental characteristics of HEAs, preparation methods, and machine learning-driven design strategies. Summarized the directional conversion and value-added research of high-entropy alloys in biomass thermal conversion intermediates. This demonstrates the excellent application adaptability of high-entropy alloys in complex reaction systems. Finally, prospects for the rational design of high-entropy alloy catalysts and their application in biomass refining technologies are outlined.

Catalysts doi: 10.3390/catal16060559

Authors: Shuai Li Sander Dekyvere Zhonghan Cheng Somboon Chaemchuen Min Jiang Cheng Chen Francis Verpoort

Recent advancements in heterogeneous catalysis have increased the interest in the synthesis of metal-free polymer-based catalysts. This work presents a novel approach for the solvent- and additive-free synthesis of a nitrogen-rich catalyst. Our unique procedure yields a non-porous organic polymer (NPOP) with a wide range of functional groups on the surface, attributed to the incomplete polymerization inherent to our solvent-free method. Detailed analysis revealed significant differences between NPOP and its Covalent Organic Framework counterpart. Remarkably, the absence of a high surface area did not hinder the efficiency of NPOP as a catalyst for the CO2 cycloaddition. The performance of NPOP exceeded that of its COF counterpart, with a conversion rate of 99% for NPOP and 35% for the COF. An observation attributed to the abundance of nitrogen functional groups on the surface of NPOP. A combination of characterizations and density functional theory (DFT) calculations was employed to thoroughly understand the working mechanism of NPOP. The imines and secondary amines on the surface function as the active sites for the ring-opening of epichlorohydrin. This study supports existing theories that N atoms can serve as nucleophiles by donating their free electron pairs. Furthermore, the distinctive synthesis procedure reported here can serve as inspiration for further design of polymer-based catalysts.

Catalysts doi: 10.3390/catal16060558

Authors: Xiaochen Liu Minyang Liu Chaofeng Ma Houlin Yu Wanjin Yu Wucan Liu

Activated carbon is a commonly used catalyst and catalyst support. Its abundant surface groups play a key role in catalytic activity and selectivity, and therefore an in-depth investigation of the surface groups of activated carbon is of great significance. The surface groups of activated carbon are diverse and structurally complex, and the corresponding characterization methods are also varied, with each technique having its own advantages and limitations. This review systematically summarizes the sources, characteristics, and effects on catalytic processes of oxygen-containing, nitrogen-containing, phosphorus-containing, and other heteroatom-containing groups on activated carbon surfaces. Emphasis is placed on the application of Boehm titration, PZC/IEP, FT-IR, XPS, TPD-MS, Raman, XRD, solid-state NMR, SEM/EDS, and EPR/ESR in the study of surface groups on activated carbon. Because the formation and alteration of surface groups on activated carbon not only change the surface chemical properties of activated carbon but also affect its structure, charge, and related properties, a single characterization method cannot accurately and comprehensively reveal its characteristics. Therefore, in practical studies, multiple characterization methods should be combined for cross-validation from the perspectives of functional group type, chemical state, thermal stability, structural changes, and catalytic behavior, so as to establish reliable correlations among “group type–structural environment–catalytic performance” and provide a basis for the rational design and optimization of activated carbon catalysts.

Catalysts doi: 10.3390/catal16060557

Authors: Pannipa Nachai Pornlada Daorattanachai Pattarapon Rungsri Navadol Laosiripojana

The efficient conversion of methane into hydrogen-rich syngas is essential for sustainable energy; however, integrating methane partial oxidation (POM) with the water–gas shift (WGS) reaction remains a significant challenge due to thermal and kinetic mismatches. This research presents a spatially decoupled dual-bed reactor configuration, utilizing Ni/GDC and Cu/GDC catalysts, to achieve synergistic hydrogen production. Unlike conventional physically mixed systems, which suffer from thermal hotspots and the unintended promotion of the endothermic Reverse Water–Gas Shift (RWGS) reaction, the dual-bed architecture effectively segregates the reaction zones. Advanced characterization, including O2-TPO and Raman spectroscopy, reveals that the GDC support acts as a critical oxygen buffer via the Mars-van Krevelen mechanism, modulating the dynamic redox state of the active metal sites to prevent deep oxidation and carbonaceous deactivation. Furthermore, macroscopic performance and carbon–oxygen mass balance analyses confirm that this rational architectural design facilitates a seamless integration of POM and WGS pathways, resulting in significantly maximized H2 yield. From a broader engineering perspective, this dual-bed strategy offers a practical, low-complexity alternative to intensive integrated technologies such as sorption-enhanced reforming (SER) or chemical looping, providing a robust and scalable framework for durable, high-efficiency hydrogen production.

Catalysts doi: 10.3390/catal16060556

Authors: Peng-Ying Jiang Ziyin Guo San Wu Shao-Hua Xiang Jun (Joelle) Wang Bin Tan

The use of water as a nucleophile in catalytic asymmetric reactions remains a significant challenge, primarily due to its intrinsically low nucleophilicity and small size, which make precise control over both reactivity and stereoselectivity particularly difficult. To address this issue, we developed a CPA-catalyzed asymmetric hydrolysis system, successfully achieving the efficient and highly stereoselective transformation of 4H-oxazines with water. Under this catalytic system, the initial formation of chiral α-bromo ketones is followed by their in situ conversion through reduction and intramolecular SN2 reactions, directly affording valuable chiral bromo alcohols and chiral oxazolone derivatives in high yields with excellent enantioselectivity.

Catalysts doi: 10.3390/catal16060555

Authors: Nesreen S. Ahmed Tamer S. Saleh Mohamed Mokhtar M. Mostafa

The principles of green chemistry—waste reduction, atom economy, safer synthesis, energy efficiency, and the use of renewable feedstocks—are intrinsically linked to catalysis [...]

Catalysts doi: 10.3390/catal16060554

Authors: Cagla Akkol Gizem Genc Birhan Tutal İsmail Uzunel Ece Tugba Saka

Steric effects refer to the effect of the size and spatial arrangement of atoms or groups on the reactions, interactions, and catalytic activities of molecules. The incorporation of Cl (chlorine) and Br (bromine) atoms as substituents into phthalocyanine (Pc) structures can have important catalytic effects. These effects arise mainly from their electronic and steric properties, which influence the behavior of the central metal ion and the overall catalyst performance. In this work, Co(II)PcQBr2 was synthesized and characterized by spectral techniques. The catalytical activity of Co(II)PcQBr2 was then evaluated for the oxidation of benzyl alcohol. The effects of the substrate/catalyst ratio, oxidant/catalyst ratio, oxidant type and temperature on the oxidation reaction of benzyl alcohol were investigated. Both catalysts exhibited high TON, TOF and total conversion yields in the presence of H2O2 as the oxidant at 50 °C. (substrate/oxidant/catalyst:1000/500/1). When the total product conversions were calculated for both catalysts, Co(II)PcQBr2 was found to have a lower product conversion (88.7%, with a TON of 914 and a TOF of 457 ) than Co(II)PcQCl2. Moreover, Co(II)PcQCl2 was determined to have higher selectivity of benzyl benzoate (94.0%, with a TON of 940 and a TOF of 470 ). The larger size of the Br atom compared to that of the Cl atom was observed to reduce catalytic activity. Considering the size of the Cl atom, it was concluded that steric effects favor the formation of benzyl benzoate by inhibiting possible side reactions, thus increasing the catalytic activity.

Catalysts doi: 10.3390/catal16060553

Authors: Amina Ledjeri Katia Madi Idris Yahiaoui Amine Aymen Assadi Mohammod Hafizur Rahman Abdeltif Amrane Farida Aissani-Benissad

This study investigates the degradation and mineralization of sulfamethazine (SMT) by an electrochemically assisted Fe3+/persulfate (electro/Fe3+/PDS) process. Experiments were conducted in a single-compartment electrochemical cell equipped with a carbon felt anode and a stainless steel cathode under constant current conditions. Compared with PDS alone and Fe3+/PDS, the combined electro/Fe3+/PDS system exhibited a strong synergistic effect, achieving up to 89.4% SMT removal within 90 min at a current intensity of 1.6 A. The enhanced performance was attributed to electrochemical Fe2+ regeneration enabling continuous activation of persulfate and generation of sulfate radicals (SO4•−). Operational parameters significantly influenced process efficiency. Increasing current intensity accelerated SMT degradation but reduced mineralization efficiency due to parasitic reactions. Under optimized conditions (I = 3 A and [Fe3+] = 1 mM), SMT degradation reached 96.83% after 60 min, while the mineralization yield attained 72.05%. Excess iron promoted radical scavenging. Similarly, a PDS concentration of 5 mM was sufficient, with higher dosages leading to self-scavenging effects. Kinetic analysis followed a pseudo first order model, with apparent rate constants decreasing at higher SMT concentrations due to radical competition. Biodegradability assays revealed a substantial increase in the BOD5/COD ratio from initially low values to 0.34 after 300 min of pretreatment, indicating improved suitability for biological post-treatment. Overall, the electro/Fe3+/PDS process represents an efficient pre-oxidation strategy for the removal of refractory antibiotics from aqueous media.

Catalysts doi: 10.3390/catal16060552

Authors: Chang-Li Xu Xiao-Mei Wu Bao-Di Ma Yi Xu

The (3aS, 6aR)-lactone serves as the key chiral intermediate for the synthesis of d-biotin. A promising approach involves the asymmetric hydrolysis of meso-dimethyl ester catalyzed by an esterase to yield the (4S, 5R)-monomethyl ester, which is subsequently reduced and cyclized to afford (3aS, 6aR)-lactone. This study first optimized the fermentation medium and culture conditions for the recombinant E. coli pET21a-EstSIT01 harboring the Microbacterium esterase gene, which exhibits high selectivity for the asymmetric synthesis of (4S, 5R)-monomethyl ester. Under optimal conditions (fermentation medium: glycerol 25 g/L, yeast extract 15 g/L, NaCl 10 g/L, MgSO4•7H2O 5 g/L; induction was initiated 2 h post-inoculation at 30 °C and pH 7.2), the enzyme activity increased 5.1-fold compared to the initial level, reaching 1072.7 U/L. Secondly, the reaction conditions for the whole-cell synthesis of (4S, 5R)-monomethyl ester catalyzed by EstSIT01 were optimized. The results indicated that organic solvents adversely affected enzyme stability, while high buffer salt concentration negatively impacted enzyme activity at elevated substrate concentrations. The optimal reaction strategy involved maintaining the pH of the aqueous reaction system at 7.5 by the controlled addition of aqueous ammonia to neutralize the (4S, 5R)-monomethyl ester produced during the reaction. Using 17.5 g/L cells and 200 mM substrate meso-dimethyl ester in deionized water, with the reaction pH mentioned at 7.5, complete conversion (100%) was achieved within 4 h at 30 °C. The space–time yield reached 441.6 g/L/d, exceeding the typical requirement for industrial biotransformation (>100 g/L/d), with 99.1% enantiomeric excess (ee) of (4S, 5R)-monomethyl ester. Finally, (4S, 5R)-monomethyl ester was reduced using sodium borohydride to synthesize (3aS, 6aR)-lactone with an ee value of 98.7%. The overall yield from meso-dimethyl ester to (3aS, 6aR)-lactone was 86.2%. These results demonstrate that this integrated chemo-enzymatic approach constitutes a greener method with promising potential for industrial application.

Catalysts doi: 10.3390/catal16060551

Authors: Youzhi Yao Ping Cheng Xiaohan Wang Qinghua Deng Tiancheng Yao Jiaxin Jiang Wenjie Wu

Monometallic nanoparticles tend to aggregate and exhibit limited catalytic performance, rendering them inadequate for high-efficiency electrocatalytic applications. In this study, a green and mild liquid-phase reduction method was employed, using sodium borohydride to simultaneously reduce graphene oxide (GO) and metal precursors. This approach enabled the uniform and highly dispersed loading of silver–copper bimetallic alloy nanoparticles (Ag1−xCux NPs) onto the surface of reduced graphene oxide (RGO). By tuning the Ag/Cu molar ratio, the size, composition, and morphology of the nanoparticles were precisely controlled. Characterization by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) confirmed that GO was efficiently reduced to RGO, and the bimetallic nanoparticles were uniformly distributed on the RGO surface in an alloy state with small particle size and no obvious agglomeration. A strong interfacial interaction between the metal nanoparticles and the support was also observed. Electrochemical tests demonstrated that the composite exhibits excellent electrocatalytic activity toward the reduction of H2O2. Notably, the reduction peak current at the Ag0.5Cu0.5NPs/RGO modified electrode was 1.8 and 2.3 times higher than those at the monometallic Ag/RGO and Cu/RGO electrodes, respectively. These results provide a reliable theoretical basis and a viable research route for the controllable synthesis of low-cost, high-performance electrocatalytic nanocomposites and their application in electrochemical H2O2 sensing.

Catalysts doi: 10.3390/catal16060550

Authors: Adem Ertürk Ilhami Gulcin

Luteolin and its derivative glycosides (cynaroside, orientin and isoorientin) are compounds with a flavonoid structure of plant origin. There are different studies in the literature on the antioxidant capacities of the structures and their inhibition effects on some enzymes. In this study, the antioxidant capacities of each structure were determined comparatively, and their inhibitory effects against enzymes associated with different diseases such as acetylcholinesterase, butyrylcholinesterase, α-glycosidase and α-amylase were evaluated by comparative investigation in vitro and in silico. Antioxidant capacities were determined for each structure by iron ions (Fe3+), cupric ions (Cu2+), Fe3+−Triphenyltetrazolium chloride (TPTZ) reduction methods and 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), N,N-dimethyl-p-phenylenediamine (DMPD) radical scavenging methods. According to the results obtained, it was determined that the antioxidant capacities of the structures were close to or better than butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), trolox, α tocopherol and ascorbic acid, which are used as standard antioxidants. The results of the study, which was conducted to determine the inhibition effects of the structures on the determined enzymes, were found to coincide experimentally and theoretically. According to the inhibition results, the best inhibitors were found as orientin (IC50: 27.729 nM) for the human carbonic anhydrase I (hCA I), cynaroside (IC50: 18.24 nM) for the human carbonic anhydrase I (hCA II), isoorientin (IC50: 1.93 nM) for the acetylcholinesterase (AChE), and cynaroside (IC50: 6.41 and 7.15 nM) for the butyrylcholinesterase (BChE) and α-glycosidase enzymes. Additionally, absorption, distribution, metabolism, and excretion (ADME) profiles and toxicity assessments of the structures were determined in a virtual environment.

Catalysts doi: 10.3390/catal16060549

Authors: Muhammad Bilal Javed Ali Zahida Bibi Tallat Munir Esraa M. Bakhsh Kalsoom Akhtar Sher Bahadar Khan

Chicken bile-mediated silver nanoparticles (Ag-NPs) were synthesized and evaluated via UV–Vis, SEM, FTIR, and XRD. The synthesis of Ag-NPs was validated by observing a color change that was visible to the naked eye and via UV–Vis spectroscopy. A peak at 435 nm in the UV–Vis spectrum suggest the formation of Ag-NPs. The FTIR spectrum indicated that Ag+ reduction into Ag-NPs may occur due to proteins that are present in chicken bile. The XRD results showed that the nanoparticles were crystalline in nature, with a crystallite size of 25 nm. The SEM images showed that spherical-shaped nanoparticles with an average size of 20–60 nm were formed. The effects of different parameters, such as extract concentration, pH, and temperature, on the shape and reaction rate of Ag-NPs were examined. The results showed that the formation of Ag-NPs increased substantially in basic medium and they were found to be more stable at 60 °C. The prepared Ag-NPs were evaluated for their antibacterial activity and photocatalytic efficiency in degrading Disperse Orange 1 (DOI) dye. The antibacterial assessment of the synthesized Ag-NPs showed significant antibacterial activity. Based on the photodegradation study, it was found that the synthesized Ag-NPs showed high activity and almost complete (97%) degradation of DOI within the first 100 min. Thus, the overall results reveal that the prepared Ag-NPs offer a better approach for remediating the aforementioned contaminants.

Catalysts doi: 10.3390/catal16060548

Authors: Xiaoying Cui Yixin Cao Yiming Dong Rui Song Zhaoping Song

Bismuth tungstate (Bi2WO6) is a typical bismuth-based visible-light-responsive semiconductor photocatalyst that has attracted significant attention in the fields of environment remediation and energy conversion. In this paper, to address the issues of high photogenerated carrier recombination rate and limited visible-light-response range of Bi2WO6, various modification strategies are highlighted, including morphology control, element doping, heterojunction construction, carbon material compositing, and coupling with functional materials such as metal–organic frameworks (MOFs), covalent organic frameworks (COFs), or conductive polymers. Furthermore, the structure–activity relationships are discussed. On this basis, the latest application progress of Bi2WO6-based photocatalysts in fields such as pollutant degradation, antibacterial activity, and energy conversion and storage is summarized. Finally, prospects are put forward regarding the existing shortcomings and future development directions in the application of Bi2WO6-based photocatalysts, aiming to provide a systematic theoretical reference for the design and application of high-performance Bi2WO6-based photocatalysts.

Catalysts doi: 10.3390/catal16060547

Authors: Özgür Yılmaz Ahmet Akif Kızılkurtlu

There is increasing interest in structured layered double hydroxide (LDH)-based catalysts because they combine tunable acid–base/redox chemistry with reactor architectures that can reduce diffusion lengths, improve heat management, and lower pressure-drop penalties. This review evaluates LDH, LDH-derived oxide (LDO/MMO), reduced metal/LDO, reconstructed hydroxide-rich, and mixed dynamic states integrated into honeycomb monoliths, open-cell foams, meshes/felts, thin films, washcoats, coated plates, microchannels, capillaries, and additively manufactured lattices. To move beyond descriptive comparison, the literature is assessed using unified evaluation dimensions: operative active state, support architecture, coating/integration route, active-phase loading, coating thickness and uniformity, reactor-volume-normalized productivity or STY, ΔP/L, axial/radial thermal gradients, time-on-stream, coating loss, regeneration recovery, and pilot-readiness. Representative benchmarks illustrate both the promise and reporting gaps of the field: NiFe-LDH-derived monoliths for CO2 methanation have reached ~70% CO2 conversion at 300 °C with >90% CH4 selectivity and only 0.7% post-test mass loss; NiFe-LDH/iron-foam monoliths retained 85% ozone conversion after 168 h; high-entropy LDH-derived oxides showed T50/T90 values of 246/254 °C for toluene oxidation; and Au/LDH capillary films achieved 31.9% glycerol carbonate yield and 3.78 g h−1 g−1 productivity. The strongest current cases are pollution abatement and CO2 methanation, whereas biomass upgrading, fine-chemical flow, high-entropy coatings, and photo/electrocatalytic films require deeper module-level validation. Overall, structured LDH catalysts should be treated as coupled chemistry–coating–reactor systems whose performance must be judged simultaneously by activity, accessible catalyst inventory, transport efficiency, pressure drop, thermal profile, durability, regeneration, and manufacturability.

Catalysts doi: 10.3390/catal16060546

Authors: Shakir Ali Isha Young-Cheol Chang

The removal of heavy oil under low-temperature conditions is a significant global challenge. This study aimed to assess the long-term whole-cell biocatalytic degradation of heavy oil in water and soil by bacteria isolated from contaminated soil in Muroran, Japan, under cold conditions. Enrichment cultures using heavy oil as the sole carbon source yielded 15 potent heavy oil-degrading isolates. However, only the C1 strain retained its activity under low-temperature conditions and was identified as Pseudomonas aeruginosa C1 using 16S rDNA sequencing. Gas chromatography analysis revealed that at 30 °C (water medium), strain C1 degraded 57% of heavy oil within 7 days. At 15 °C, the degradation efficiency of C1 declined due to a temperature-dependent metabolic lag phase (1 day); however, at 15 °C, 70% degradation was observed in seven days. In long-term experiments at 5 °C and 10 °C, 35% and 40% degradation were recorded for C1 after 98 days. In artificially contaminated soil at 5 °C, C1 achieved 60% biodegradation. These results demonstrate cold-adapted whole-cell activity against heavy oil and motivate the design of controlled, contained ex situ reactors (e.g., enzyme-based or cell-free systems) for safe remediation in cold climates.

Catalysts doi: 10.3390/catal16060545

Authors: Jiahui Zhang Minghan Li Xiang Liang Yanping Ma Junge Li Shun Li Hong Jiang

A novel K-resistant CeSbTi mixed oxide catalyst was prepared by co-precipitation method for ammonia selective catalytic reduction (NH3-SCR) of NOx. The experimental results show that the introduction of Sb2O5 can significantly improve the catalytic activity of the CeTi catalyst. The modulated CeSbTi catalyst has good resistance to K, and the NOx conversion rate was as high as 95% after K poisoning. Its superior catalytic activity could be ascribed to the large specific surface area with increased acid sites and more oxygen defects and Ce3+ species after the introduction of Sb2O5, which prompt NH3 adsorption and activation. In addition, NH3-SCR reaction over CeSbTi and K/CeSbTi catalysts follows the E-R mechanism. The introduced Sb-O bond as the base capture site preferentially binds to potassium and releases part of the active Ce sites, thus retaining more acid sites and oxygen defects to a certain extent.

Catalysts doi: 10.3390/catal16060544

Authors: Xueting Shi Wei Yan Jun Lu Ranran Zhou Qijie Jin Liguo Chen Mutao Xu Changcheng Zhou Haitao Xu

To efficiently degrade tetracycline (TC) antibiotic pollution, cobalt-based (Co-OMCs/F) and cobalt–copper bimetallic ((Co+Cu)-OMCs/F) monolithic mesoporous carbon catalysts were synthesized using resorcinol–formaldehyde resin as a carbon precursor, with hexamethylenetetramine (HMT) and formaldehyde (CH2O) as crosslinking agents, followed by high-temperature carbonization under N2. The materials were characterized by XRD, SEM-EDX, HRTEM, and EPR. Key factors-metal loading, PMS concentration, initial pH, and flow rate-were investigated for their effects on TC degradation. Degradation mechanisms and stability were assessed via radical quenching and continuous-flow cycling tests. Results show optimal performance at a cobalt loading of 0.6 g. Compared to CH2O, HMT favors a three-dimensional interconnected mesoporous carbon framework with uniform metal distribution and high crystallinity. Under conditions of 25 mg/L TC, 0.33 mmol/L PMS, pH 7, and 2 mL/min flow rate, the (Co+Cu)-OMCs/F (HMT) catalyst achieved ~93% TC degradation over 9 h of continuous operation, and 95% after three reuse cycles, significantly outperforming the single-metal Cu-OMCs/F catalyst. Radical quenching and EPR identified superoxide radicals (·O2−) as the dominant active species (~78% contribution), with sulfate radicals (SO4·−), hydroxyl radicals (·OH), and singlet oxygen (1O2) playing synergistic roles. The synergistic Co-Cu bimetallic effect, combined with the confinement effect of the mesoporous carbon support and HMT-induced uniform nucleation, endows the catalyst with high activity and long-term stability. This work provides a theoretical basis for designing efficient, reusable, monolithic mesoporous carbon-based PMS activation catalysts for advanced antibiotic wastewater treatment.

Catalysts doi: 10.3390/catal16060543

Authors: Gulim Jetpisbayeva Nurbanu Sarova Gulnaziya Seitbekova

The selective conversion of syngas (CO + H2) to higher alcohols (C2+OH) via Fischer–Tropsch synthesis (FTS) is a strategically important but challenging process, requiring catalysts that can simultaneously sustain C–C chain growth and preserve C–O bonds in reactive intermediates. Over the past decade (2015–2025), perovskite-type complex oxides with the formula ABO3 have emerged as powerful precatalysts for this application, with LaCoO3 attracting particular attention due to its structural flexibility, controllable reducibility, and the unique catalytic role of the La2O3 phase formed upon reduction. This review systematically covers recent advances in synthesis strategies for LaCoO3 and substituted perovskites, including sol–gel, co-precipitation, mechanochemical, and template-assisted (KIT-6, SBA-15) methods; effects of A-site (Sr) and B-site (Cu, Ga, Ni, Mn) substitution on reducibility, active phase dispersion, and product selectivity; alkali promotion and its interaction with the perovskite-derived active phase; mechanistic understanding of the alcohol-forming pathway, including the Co0/Co3+ bifunctional site concept, CO insertion mechanism, and the role of La2O3 in suppressing the Boudouard reaction; and catalyst stability and deactivation pathways under FTS conditions. Original data from LaCoO3 catalysts prepared by co-precipitation with ethylene glycol (LCO-1: S_KOH = 90%, Y_KOH = 57 mg·g−1·h−1) and via citrate/KIT-6 template synthesis (LCO/KIT-6: Y_KOH = 80 mg·g−1·h−1, S_BET = 220 m2/g) at 240 °C and 2 MPa serve as the primary experimental reference throughout. Key challenges, including the surface area–selectivity trade-off, long-term stability under industrial conditions, and opportunities in CO2 hydrogenation, are critically discussed.

Catalysts doi: 10.3390/catal16060542

Authors: Yongyue Bai Mingguan Xie Huili Yu Langyou Wen Hui Yuan Yongrui Wang Youhao Xu Xingtian Shu

An efficient catalyst for the reaction of ethanol–acetaldehyde into 1,3-butadiene (EATB) is prepared through the grafting of zirconia into a zeolite Beta lattice. The grafting is achieved through the dealumination of a zeolite framework by acid treatment followed by zirconia impregnation, leading to the substitution of aluminum in the zeolite framework by zirconia. The catalyst with zirconia grafted into the zeolite framework promotes desirable catalyst properties like high zirconium dispersion, stability, and the close proximity of Lewis acid, Bronsted acid, and medium basic sites. The phase, the coordination of zirconia, the location of the active center and the cooperative synergism were elucidated through various characterization techniques, including X-ray diffraction, Raman spectroscopy, N2 adsorption, UV–vis spectroscopy, XPS, 29Si MAS NMR, NH3-TPD, Py-IR, CO-IR and CO2-TPD. The catalytic results show that a suitable phase and content of zirconia were needed to improve the ethanol–acetaldehyde conversion, butadiene selectivity and catalyst stability. Among the catalysts, m+t-ZrOx-Beta-H2O-9020 (m = monoclinic, t = tetragonal ZrO2 phase) achieved the best butadiene selectivity of 82–73% at the conversion of 100–66%, run over 200 h. The results allow us to propose a Lewis acid–medium basic pairing for the Si–O–Zr–O–Si group, where the adjacent Si-OH is the active center for reactions.

Catalysts doi: 10.3390/catal16060541

Authors: Sarra Karoui Mohamed Aziz Hajjaji Ahmed Amine Azzaz Oussama Baaloudj Mohamed el Kebir Mohammod Hafizur Rahman Amine Aymen Assadi

This study investigates the simultaneous elimination of ethyl acetate (EA), a representative volatile organic compound (VOC), and Escherichia coli aerosols from indoor air using a continuous-flow dielectric barrier discharge (DBD) plasma reactor coupled with a photocatalytic luminous textile system (Cu/TiO2-coated fibers). The effects of applied voltage, relative humidity, and air-flow rate on pollutant removal and disinfection performance were systematically evaluated. Optimal DBD operation at 18 kV, 1 m3 h−1 airflow, and 70% relative humidity achieved single-process removal efficiencies of 77% for EA and 2 log reduction (CFU mL−1) for E. coli. When photocatalysis was coupled with DBD plasma, a significant combined effect was observed, increasing EA degradation to 87% and bacterial inactivation to 3.8 log (CFU mL−1). The coupling enhanced active-species generation, improved CO2 selectivity (up to 53%), and reduced residual ozone concentration. Humidity positively affected microbial inactivation due to °OH radical formation but slightly decreased VOC degradation by limiting ozone regeneration. Results demonstrate the efficiency and scalability of the DBD–photocatalysis hybrid system for multi-pollutant indoor air purification, offering rapid, low-temperature treatment suitable for industrial-scale applications.

Catalysts doi: 10.3390/catal16060540

Authors: Jinlong Wang Yaheng Li Kinjal J. Shah Mengtian Lu Chengzhang Zhu Yang Wu Dong Jiang Zhongmin Wang Yongjun Sun

The purpose of this study was to investigate the effectiveness and mechanism of iron-based catalysts in the treatment of phenolic wastewater by catalyzing ozone oxidation. The removal rates of phenolics and COD were systematically examined using simulation experiments with water and actual wastewater, which involved analyzing the effects of reaction time, pH, ozone dosage, catalyst dosage, and initial concentration. The phenol and COD removal rates in the simulated wastewater were 95.9% and 93.5%, respectively, respectively, while the ozone dosage was 16 mg/L/min, pH was 6.7–6.8, and catalyst dosage was 0.3 g/L. The phenol and COD removal rates in the actual wastewater were 68.6% and 68.0%, respectively. The reaction time was 30 min. The system’s efficient removal ability for phenolic compounds, polycyclic aromatic hydrocarbons, and others was confirmed through three-dimensional fluorescence and ultraviolet spectroscopy. The iron-based catalyst generates ·OH through three pathways: adsorption of activated ozone on surface active sites, continuous production of free radicals by Fe2+/Fe3+ cycling, and direct activation of ozone by Fe2+. This mechanism analysis showed that the catalyst generates ·OH. These pathways convert pollutants into small molecules or mineralized by attacking the aromatic rings and conjugated structures of pollutants. Technical references for the deep treatment of phenol-containing wastewater are provided in this study.

Catalysts doi: 10.3390/catal16060539

Authors: Kairat Kadirbekov Nurdaulet Buzayev Almaz Kadirbekov Nurgul Shadin Yersin Tussupkaliyev Asylbek Yespenbetov

The selective conversion of high-molecular-weight paraffins (C20–C40) into linear alpha-olefins is often hindered by severe diffusion limitations and secondary over-cracking. This study addresses these challenges by transforming low-value natural minerals into sophisticated catalytic systems. We present a “top-down” engineering strategy for designing hierarchical catalysts based on natural Kazakhstani clinoptilolite. The multi-stage modification involves synergistic demineralization and precision chelation (EDTA, sulfosalicylic acid) to generate a tailored mesoporous architecture. This framework serves as a host for the sub-nanometric immobilization of Keggin-type heteropolyacids (PW12, PMo12), ensuring optimal active-phase dispersion. The innovative dual-step modification successfully bypassed the “micropore barrier”, creating a high-surface-area hierarchical network that facilitates the transport of bulky paraffinic molecules. Precise localization of heteropolyacid clusters within the created mesopores resulted in the formation of superstrong Lewis acid sites, as confirmed via temperature-programmed ammonia desorption. These sites triggered a highly efficient monomolecular beta-scission mechanism, suppressing undesirable hydrogen transfer reactions. The resulting catalysts achieved a breakthrough in technical paraffin cracking, delivering a 70% liquid product yield with an unprecedented >50% selectivity toward the C7–C14 α-olefin fraction. This work demonstrates a sustainable pathway for upgrading natural zeolites into high-performance, green catalysts that rival expensive analogs in precision and efficiency.

Catalysts doi: 10.3390/catal16060538

Authors: Aminur Rahman Md Mahbubur Rahman Md Azizul Haque Pottathil Shinu Muhammad Muhitur Rahman Aftab Ahmad Khan Sayeed Rushd

The emergence and the growing influence of contaminants in wastewater has driven the development of advanced and efficient treatment technologies. Catalysts based on biochar have become a promising material because of their cheapness, adjustable physicochemical characteristics, and environmental compatibility. This study comprehensively reviews recent developments in biochar-based catalytic processes to treat wastewater with an emphasis on AOPs and photocatalysis. The main categories of catalysts including metal-loaded biochar, heteroatom-doped biochar, biochar-supported semiconductor composites, and magnetic biochar are extensively discussed with regard to their synthesis, structure, and performance in the elimination of organic, emerging, and heavy metal contaminants. Emphasis is placed on catalytic reactions, radical (•OH, SO4•−) and non-radical (singlet oxygen and electron transfer) reactions, as well as the effect of functional groups on the surface, defects, and electronic features in the control of activity. Engineered biochar has a better performance in charge separation, reactive species generation, and synergistic interactions between adsorption and degradation. Nevertheless, there are issues such as heterogeneity in biochar properties, insufficient understanding of structure–activity interactions, catalyst stability, and the absence of studies of biochar under real wastewater conditions. The future perspectives focus on rational catalyst design, integration of processes, and scaling up to practical applications. Overall, biochar-based catalysts have emerged as a sustainable platform for advanced wastewater treatment, but additional studies are needed to enable their large-scale use.

Catalysts doi: 10.3390/catal16060537

Authors: Shiang He Shikun Zhong Yueqin Zhang Lingtao Liu Youhao Xu

To investigate the modulation effects of high temperature and molecular sieve acidity on olefin cracking pathways and product selectivity, the catalytic cracking performance of 1-pentene was systematically studied under catalytic cracking temperatures of 700, 750 and 800 °C over H-ZSM-5 molecular sieves with silica-alumina molar ratios (SAR) of 23, 42 and 95. The contributions of catalytic cracking and thermal cracking were quantified, and the synergistic effects of temperature and SAR on monomolecular cracking, bimolecular cracking, confined catalytic radical (CCR) reaction and side reactions were analyzed by composition of the cracking products. Results showed that catalytic cracking dominated the cracking of 1-pentene over H-ZSM-5 in 700–800 °C. Higher temperature promoted monomolecular cracking and CCR, thus significantly increasing ethylene selectivity. Lower SAR enhanced acidity and catalytic cracking activity but intensified aromatization and C5+ formation. HZ-95 with weak acidity favored bimolecular cracking and exhibited low ethylene selectivity. HZ-42 achieved the optimal performance at 800 °C, with 1-pentene conversion of 98.80% and ethylene molar selectivity of 82.41%; both hydrogen transfer reactions and methane formation were effectively suppressed. This work provides mechanistic insights and theoretical support for the targeted catalytic cracking to olefins (TCO) process.

Catalysts doi: 10.3390/catal16060536

Authors: Muhammad Raza Su-Hong Kim Min-Sik Kang Jae-Hyeob Kim Gi-Seong Moon Arunporn Itharat Jun-Sub Kim Hyang-Yeol Lee

Cosmetic preservatives should have reduced percutaneous absorption to lower the risk of systemic exposure and skin irritation. In this work, previously synthesized galactosylated derivatives of common cosmetic preservatives were comparatively evaluated for transdermal permeation and preliminary toxicity. Escherichia coli β-galactosidase was used to enzymatically modify several of the commonly used cosmetic preservatives to produce their corresponding galactosylated derivatives: benzyl alcohol β-d-galactopyranoside 7, 2-phenoxyethanol β-d-galactopyranoside 8, chlorphenesin β-d-galactopyranoside 9, 1,2-hexanediol β-d-galactopyranoside 10, 1,2-octanediol β-d-galactopyranoside 11, and 2-phenylethyl β-d-galactopyranoside 12. HPLC and NMR spectroscopy were used to analyze the previously synthesized derivatives. The Franz diffusion cell assay was used to evaluate skin penetration. 2-Phenoxyethanol (PE), chlorphenesin (CPN), and 2-phenylethanol (PhE), showed measurable skin penetration, with flux values ranging from 3.82 to 7.34 µg·h−1·cm−2 and permeability coefficients (Kp) between 1.38 and 3.00 × 10−3 cm·h−1. In contrast, their galactosylated derivatives showed markedly reduced permeation under the same experimental conditions. Moreover, brine shrimp lethality assays indicated that galactosylated derivatives had significantly higher LD50 values (1.6–2.1 mg/mL) than their parent compounds (0.1–0.79 mg/mL), suggesting lower cytotoxicity. These findings suggest that enzymatic galactosylation can significantly decrease skin permeability and the toxicity of cosmetic preservatives, highlighting its potential approach to improve the safety of cosmetic components.

Catalysts doi: 10.3390/catal16060535

Authors: Alfonso Navarro-Montejo Carlos Pacheco Abimael Rodriguez Enrique Escobedo Romeli Barbosa

The electrochemical performance of hydrogen compressors (EHCs) depends critically on the hierarchical microstructure of their catalyst layers (CLs), where platinum, carbon, and ionomer phases govern coupled charge and mass transport across nanometric (Nano) and mesoporous (Meso) scales, the latter characterized by agglomerate and pore phases. This work presents an experimental–computational framework to establish quantitative microstructure–transport–performance relationships in EHC CLs. CLs were fabricated by electrospray deposition on Nafion® 117 membranes and characterized by scanning electron microscopy, from which 33 representative Meso MCs were extracted and used to assemble an EHC cell for experimental polarization curves. Statistically equivalent Nano MCs resolved phase connectivity within the agglomerate phase and determined the effective catalyst area from neighboring phase configurations. Effective transport coefficients for electronic conductivity, protonic conductivity, and H2 diffusivity were computed via the finite volume method and multiscale-coupled into an analytical polarization model. Electronic and protonic conductivities are controlled by conductive-phase connectivity at the Nano scale, while H2 diffusivity is governed by the pore fraction and spatial distribution at the Meso scale, with variations exceeding three orders of magnitude. Multiscale transport coupling factors obtained via inverse calibration reduced model–experiment discrepancies to 0.05 V, validating the framework for EHC electrode design.

Catalysts doi: 10.3390/catal16060534

Authors: Zishi Zhang Yang Ruan

The catalytic removal of refractory VOCs in gas–solid reactions usually suffers from the formation of toxic byproducts and catalyst deactivation. The advanced oxidation process (AOP) wet scrubber has recently attracted interest in VOCs purification due to its high efficiency and inhibited gaseous byproducts emission. MOFs/metal sulfides (termed M50C50) were designed to activate peroxymonosulfate (PMS) for toluene removal in a wet scrubber. The heterojunction interface synergistically couples MIL-100(Fe) and CoS for dual functions, the M50C50 enabled the rapid transfer the toluene from the gas phase to the aqueous phase, where they were subsequently mineralized by SO4•− and •OH radicals. The primary active sites responsible for PMS activation were identified as reducing sulfur species, along with low-valence cobalt and iron species. Over 90% of toluene were removed with a wide pH range, while •OH and SO4•− were involved in the mineralization of intermediates. The process showed high mineralization efficiency (75% CO2 evolution) and effectively reduced the formation of toxic byproducts, underscoring its potential for minimizing secondary pollution risks. This work provides a novel route to designing composite catalysts for deep VOC oxidation via AOP wet scrubbers, greatly facilitating their use in environmental remediation.

Catalysts doi: 10.3390/catal16060533

Authors: Yanhui Xu Rongjun Xia Xingxing Ji Jiwen Hu Fangzhi Huang

In nitrate electrochemical reduction reaction (NO3RR), competing side reactions like hydrogen evolution often lead to poor selectivity and subpar kinetics, limiting practical use. Herein, using iron oxyhydroxide nanoarrays grown on a titanium mesh as the substrate, silver nanoparticles were introduced onto the tips of the iron oxyhydroxide nanowires via electrochemical deposition, thereby forming an Ag/FeOOH heterojunction electrocatalyst. At −0.85 V, Ag/FeOOH demonstrates excellent performance, with 97.56% ammonium selectivity, 92.45% nitrate conversion rate, and an ammonium yield of 3.21 mg h−1 cm−2. Furthermore, the Zn-NO3− battery exhibited a power density of 1.28 mW cm−2. Ag/FeOOH’s structure enhances interfacial nitrate adsorption and reduces NO3RR energy barriers, accelerating reaction kinetics. It promotes NO3−-to-NO2− conversion via dual-site synergy, boosting NH4+ yield and advancing electrocatalyst design.

Catalysts doi: 10.3390/catal16060532

Authors: Ramesh Kanthasamy

The need for a transition to a low-carbon economy has led to the growing demand for hydrogen as a clean energy source. Hence, ethanol steam reforming (ESR) is one of the promising technological pathways for hydrogen production. Ethanol, which is the major feedstock, can be obtained from abundant biomass. However, one of the major drawbacks is catalyst deactivation due to the high temperature requirement to start the reaction. This study therefore focused on employing a response surface approach to optimize the operating conditions (reaction temperature, steam-to-ethanol ratio and catalyst amount) of ethanol steam reforming over an Iridium-promoted Ni/MCM-41 catalyst. The Iridium-promoted Ni/MCM-41 catalyst was synthesized using the sequential wet impregnation method and characterized using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), N2 physisorption analysis, and X-ray diffraction (XRD). A central composite experiment design (CCD) was employed to study the effect of the variables on the hydrogen production from the ESR. The catalytic efficacy was ascertained by evaluating the H2 yield under varied experimental conditions provided by the CCD. The characterization of the catalyst revealed well-dispersed Ir and Ni nanoparticles on a mesoporous MCM-41 support. Catalytic evaluations indicate that the H2 yield was most influenced by the reaction temperature (correlation coefficient of 0.68), followed by the catalyst amount (correlation coefficient of 0.34) and steam-to-ethanol ratio (correlation coefficient of 0.28). A maximum H2 yield of 5.82 mol/mol ethanol was obtained at 798.11 °C, a steam-to-ethanol ratio of 3.40, and 1.25 g of catalyst. These findings underscore the importance of Ir-promoted Ni/MCM-41 catalyst for efficient H2 production, highlighting the reaction temperature as a critical parameter for process optimization.

Catalysts doi: 10.3390/catal16060531

Authors: Chien-Yie Tsay Tai-Ting Ho

The objective of this study is to develop a nanosized, visible-light-responsive photocatalyst with magnetic separability and recyclability for repeated use. Spinel ferrite nanoparticles, which are environmentally friendly, are promising candidates for achieving this goal. Spinel ferrite nanoparticles were synthesized via a low-temperature hydrothermal method to investigate their microstructural characteristics, magnetic properties, and photocatalytic performance. Initially, four ternary spinel ferrite (MFe2O4, where M = Mg, Mn, Co, and Zn) nanoparticles were compared in terms of their physical properties and photodegradation efficiencies of organic dye methylene blue (MB). Among them, the MgFe2O4 and ZnFe2O4 samples exhibited superior photocatalytic activity compared to the MnFe2O4 and CoFe2O4 samples. Subsequently, a systematic investigation of the Zn–Mg ferrite system (Zn1−xMgxFe2O4, x = 0 to 0.8 in increments of 0.2) was carried out. The results revealed that the x = 0.8 samples achieved the highest photodegradation efficiency of 99 for a 10 MB aqueous solution under visible-light irradiation for 90 min. This improved performance is attributed to formation of a heterojunction of Zn–Mg nanoferrite/Fe2O3, which promotes light harvesting and prevents photogenerated charge recommendation, thus significantly improving photocatalytic activity.

Catalysts doi: 10.3390/catal16060530

Authors: Orhan Baytar Metin Zontul Ceren Orak Seda Karateke Hakan Aydın Sabit Horoz

This study comprehensively investigates the degradation performance of a Mn-doped Zn2SnO4 photocatalyst based on time-dependent UV-Vis absorption spectra. Before machine learning modelling, the effects of experimental parameters such as UV–Vis measurement wavelength, reaction time, and Mn doping ratio were statistically validated using One-Way Analysis of Variance (ANOVA) and Multiple Linear Regression (MLR) methods. To overcome the limitations of linear models in representing complex physical systems, an optimized Multi-Layer Perceptron (MLP) architecture was developed to capture the system’s nonlinear dynamics with high accuracy. To validate the model’s out-of-sample prediction capability and prevent data leakage potentially arising from spectral data correlation, the “Leave-One-Doping-Level-Out” (LODLO) cross-validation strategy was applied, during which performance metrics of R2=0.8889 and MSE=0.00238 were recorded. To make the neural network’s decision-making mechanism transparent, a dual-validation explainability framework comprising Shapley Additive Explanations (SHAP) and Permutation Feature Importance analyses was employed. By quantifying the relative contributions of the experimental parameters to the model predictions, this approach revealed that the UV–Vis measurement wavelength was the dominant predictive variable, followed by the Mn doping ratio and reaction time. This study presents a transparent methodology that offers both strong predictive capability and physically grounded data to shed light on the complex interactions in doped semiconductor photocatalysts.

Catalysts doi: 10.3390/catal16060529

Authors: Tao Zhang Zhigang Zhang Yuan Tian Xusheng Zhao Yuchun Ye Jiaqi Qiu Jie Wu Zhongqing Yang

Direct emission of low-concentration methane not only aggravates global warming but also causes serious energy waste. Catalytic combustion is considered an effective strategy for methane abatement because it enables methane oxidation at relatively low temperatures. In this work, a series of Mn–Ce–Cu/γ-Al2O3 catalysts with different nominal Mn/Ce ratios were prepared by the incipient wetness impregnation method and applied to low-concentration methane catalytic combustion. The results showed that Mn–Ce co-modification significantly improved the activity of Cu/γ-Al2O3 catalysts, and the catalytic performance strongly depended on the Mn/Ce ratio. Among all samples, 7Mn-3Ce-10Cu exhibited the best activity, with the temperatures required for 10%, 50% and 90% methane conversion (T10, T50 and T90) of 380.8, 427.3 and 478.7 °C, respectively. Apparent activation energy (Ea) analysis further showed that 7Mn-3Ce-10Cu possessed the lowest Ea value of 83.81 kJ mol−1, indicating that the optimized Mn/Ce ratio effectively lowered the apparent kinetic barrier for methane oxidation. X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen (N2) adsorption–desorption results suggested that Mn–Ce co-modification changed the phase composition, improved the dispersion state of active oxide species and generated a more favorable pore structure for reactant diffusion. Oxygen temperature-programmed desorption (O2-TPD) and X-ray photoelectron spectroscopy (XPS) results further indicated that the enhanced activity of 7Mn-3Ce-10Cu was closely associated with improved oxygen desorption behavior, a higher proportion of surface oxygen species and favorable surface redox characteristics of Cu, Mn and Ce species. Moreover, 7Mn-3Ce-10Cu maintained methane conversion above 90% during a 50 h stability test at 500 °C, and the inhibition caused by 5% H2O was partially reversible. These results demonstrate that Mn–Ce co-modification is an effective strategy for improving low-cost Cu-based catalysts for low-concentration methane combustion.

Catalysts doi: 10.3390/catal16060528

Authors: Shaohua Chai Minke Huang Shuangde Li Wenbo Zhang Baikang Zhu Yunfa Chen

Plasma-catalytic oxidation is a promising approach for the abatement of volatile organic compounds (VOCs), yet its efficiency is often limited by the ineffective utilization of plasma-generated reactive oxygen species and incomplete oxidation pathways. In this work, a composite catalyst was constructed by integrating spinel-type NiCo2O4 with three-dimensional cubic mesoporous KIT-6 to couple efficient mass transfer with redox-active surface functionality for plasma-catalytic degradation of toluene. The performance of NiCo/KIT-6 was systematically evaluated in a dielectric barrier discharge (DBD) reactor and compared with Ni/KIT-6, Co/KIT-6, and NTP-only systems. XPS, O2-TPD, H2-TPR, and apparent dielectric measurements were employed to elucidate catalyst properties relevant to plasma–surface interactions. NiCo/KIT-6 exhibits superior overall performance in terms of toluene conversion, COx selectivity, and CO2 selectivity over a wide range of specific input energies. This enhancement is closely associated with the integrated regulation of surface redox properties, oxygen activation capability, and apparent dielectric response by the NiCo2O4/KIT-6 composite structure, which may promote reactive oxygen utilization and facilitates effective plasma–surface redox processes. These results provide insights into the rational design of composite catalysts for plasma-assisted oxidation of aromatic VOCs.

Catalysts doi: 10.3390/catal16060527

Authors: Yilin Niu Bozhong Tian Jingrui Duan Wen Luo Yang Wu Yifan Zhang

This work targets efficient visible-light-driven hydrogen evolution by construction of a dendritic CdS-based photocatalytic system decorated with Pt-Ni bimetallic cocatalysts (CdS@PtNi). The dendritic CdS was synthesized via a hydrothermal method, followed by in situ deposition of Pt and Ni using NaBH4 chemical reduction, with cocatalyst loading tuned between 2 and 5 wt%. Among them, C@PN4 (4 wt% total metal loading) demonstrated the best performance, with a bandgap of ~2.15 eV. XRD results show that the samples retain the hexagonal CdS phase without significant impurities. SEM/TEM and elemental mapping confirm uniform dispersion of Pt and Ni, forming intimate interfaces with CdS. XPS results reveal positive shifts in S 2p and Cd 3d binding energies, indicating that the bimetallic cocatalyst promotes electron transfer from CdS to the metals and enhances interfacial coupling. Photoelectrochemical analysis shows C@PN4 features enhanced absorption above 500 nm, significantly reduced PL, extended carrier lifetime, higher transient photocurrent, and lower charge-transfer resistance, suggesting greater efficiency in charge separation and transport. Band structure analysis reveals a negative shift of the conduction band to a more reductive potential. In photocatalytic tests, C@PN4 achieves an H2 yield of 15.6 mmol g−1 over 4 h (3.9 mmol g−1 h−1), with <5% activity loss after four cycles. AQY reaches 0.0483% at 420 nm, with a monochromatic photon-to-hydrogen conversion efficiency (MPH) of up to 2.01%. Mechanistically, the Pt/CdS Schottky junction drives directional electron extraction, while Ni likely synergistically optimizes interfacial electronic distribution and facilitates water activation/dissociation; together, they accelerate surface reaction kinetics and suppress photocorrosion, achieving efficient and stable hydrogen evolution with low noble metal loading.

Catalysts doi: 10.3390/catal16060526

Authors: Yuyang Zu Keda Wang Jing Yu

To address the dual dilemmas of energy shortage and environmental pollution caused by excessive consumption of fossil fuels, semiconductor photocatalysis has been regarded as a promising sustainable technical route. As a novel metal-free polymeric semiconductor, graphitic carbon nitride (g-C3N4) has become a benchmark material in photocatalysis due to its suitable visible light response, excellent band structure, high stability, and low-cost raw materials. This review systematically elaborates the structural characteristics, photocatalytic mechanism and mainstream synthetic methods of g-C3N4, summarizes the performance optimization strategies, sorts out its application progress in environmental remediation and energy conversion, analyzes the core bottlenecks of current research and prospects the future directions, providing a systematic reference for the fundamental research and industrial application of g-C3N4-based photocatalysts.

Catalysts doi: 10.3390/catal16060525

Authors: Linwei Jiang Poh Lin Lau Huaiyuan Kang Bosong Duan Aixiang Wang Hsien-Yi Hsu Zongyou Yin Guohua Jia

The high energy consumption of water electrolysis is primarily limited by the sluggish oxygen evolution reaction (OER). Replacing the OER with thermodynamically favorable anodic reactions provides an effective strategy to improve energy efficiency. Among these reactions, the sulfide oxidation reaction (SOR) offers both low thermodynamic potential and environmental relevance. In this work, we develop a high-entropy metal sulfide catalyst, CuNiCoFeMnS, via a facile aqueous synthesis route, achieving homogeneous elemental dispersion and a highly disordered structure. The catalyst exhibits excellent SOR activity, delivering a low potential of 0.396 V to achieve a current density of 10 mA cm−2. In addition, it enables a significant reduction of 1.05 V in cell voltage at 50 mA cm−2 compared with conventional water electrolysis. Furthermore, by integrating solar energy, the system enables simultaneous upgrading of sulfide-containing wastewater and energy-efficient hydrogen production. These results demonstrate a promising pathway toward coupling waste remediation with sustainable hydrogen generation.

Catalysts doi: 10.3390/catal16060524

Authors: Joseph McCaig H. Henry Lamb

Ni/Siral catalysts with different Si/Al ratios were prepared by incipient wetness impregnation (IWI) to assess the impact of support composition on Ni2+ speciation and ethylene oligomerization (EO) performance. The catalysts were characterized by X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (TPR), X-ray diffraction (XRD), NH3 temperature-programmed desorption (TPD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) with energy-dispersive X-ray (EDX) analysis, and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS). The EO catalysts were tested in a fixed-bed reactor at 225 °C under 11 bar ethylene and at 120 °C under 26 bar ethylene. Ni/Siral-70 was the most active catalyst investigated, but Ni/Siral-30 also exhibited good performance. The active sites were inferred to be isolated Ni2+ ions on amorphous SiO2-Al2O3 containing interstitial Al3+ ions that enhance Brønsted acidity; Ni/Siral-70 displayed the highest concentration of these sites based on CO DRIFTS. Formation of NiAl2O4 surface species limited the activity of Ni/Siral-30 and especially Ni/Siral-5. The catalysts were also tested using a simulated ethane oxidative dehydrogenation (ODH) product stream containing 44% ethylene, 44% ethane, 4.5% methane, 2% H2, 4.5% CO2, 0.9% propylene, and 0.1% CO. The simulated ODH mixture gave lower EO conversion than 50/50 ethylene/N2 at 225 °C and 11 bar over Ni/Siral-30, consistent with catalyst poisoning. In contrast, EO conversion over the Ni/Siral-70 catalyst was unaffected under these conditions. Catalyst testing at 120 °C and 26 bar revealed catalyst poisoning by feed impurities for both catalysts. Low-temperature/high-pressure EO activity was not recovered by simple thermal regeneration of Ni/Siral-30 at 300 °C.

Catalysts doi: 10.3390/catal16060523

Authors: Jianqing Zhou Xiaodong Cui Jie Zhang Senhua Ke Linfeng Fei Lun Yang Wanping Chen

A surprising tribocatalytic capability has been discovered for Si single crystals to convert mechanical energy into chemical energy for organic dye degradation recently. In this study, their tribocatalytic capability has been explored for converting mechanical energy into chemical energy of water splitting. In glass reactors with Si single crystals coated on the bottoms and with H2O and N2 enclosed, Al2O3 nanoparticles, TiO2 nanoparticles, and NiO particles were stimulated through magnetic stirring using home-made PTFE magnetic rotary disks separately. For Al2O3 nanoparticles, as much as 14,330 and 41,964 ppm H2 were produced after 1 and 3 h of 400 rpm magnetic stirring, respectively, much higher than those obtained for TiO2 and NiO, and for Al2O3 nanoparticles in glass-bottomed reactors as well. The tribocatalytic production of H2 was further explored with respect to NaCl addition to H2O and p/n doping in Si, with negative effects observed for them all. Photoluminescence spectroscopy revealed continuous generation of hydroxyl radicals in the course of magnetic stirring, which supports a tribocatalytic mechanism based on the excitation of electron–hole pairs in Si single crystals through mechanical energy absorbed through friction. These findings suggest a great potential for narrow-band semiconductors to utilize mechanical energy through friction to carry out important chemical reactions.

Catalysts doi: 10.3390/catal16060522

Authors: Sebastian Drużyński Adriana Wróbel-Kaszanek Bartłomiej Igliński Urszula Kiełkowska Krzysztof Mazurek

The growing demand for vanadium and the environmental threat associated with spent catalyst masses have sparked widespread scientific interest in the recovery of V2O5 from deactivated vanadium-based catalysts, including those used in sulphuric(VI) acid production. This review places vanadium(V) recovery in the broader context of resource efficiency and the circular economy. The main deactivation mechanisms are analysed, including poisoning, sintering, and structural changes affecting catalytic activity and vanadium availability. Hydrometallurgical approaches to vanadium recovery are discussed, with a particular focus on leaching agents, vanadium speciation in aqueous media, and subsequent separation techniques such as adsorption, solvent extraction, and vanadium(V) precipitation. Key process parameters influencing recovery efficiency, including temperature, pH, and caustic composition, are discussed to provide a comparative assessment of existing methods. The analysis highlights the advantages and limitations of current recovery methods and identifies gaps related to selectivity, process integration, and environmental impact. Overall, the study demonstrates that effective V2O5 recovery requires a thorough understanding of catalyst deactivation and solution chemistry. It also outlines models for developing more sustainable and economically viable recycling strategies.

Catalysts doi: 10.3390/catal16060521

Authors: Merlín Rosales Federico Arrieta Juan Carlos Drosos-Ramirez

Transfer hydroformylation of alkenes with formaldehyde constitutes a green and sustainable route to aldehydes. In this work, the transfer hydroformylation of styrene with formaldehyde was efficiently catalyzed by [Rh(κ2-dppe)2]+ (A), where dppe stands for 1,2-bis(diphenylphosphino)ethane. The reaction was found to be first order with respect to both Rh and substrate concentrations and fractional order with respect to formaldehyde concentration, in line with the behavior previously reported for 1-hexene. DFT was used to investigate the reaction mechanism by using ethene and [Rh(κ2-dpe)2]+ (A), where dpe stands for 1,2-bis(phosphine)ethane, as simplified models of the substrate and catalyst, respectively, and by considering several functionals. The DFT calculations indicate that M06-L provides the most suitable description of the thermodynamic and activation parameters associated with the elementary steps. The combined analysis of kinetic results and the DFT calculations allowed us to propose a detailed catalytic cycle for this reaction, initiated by the reversible oxidative addition of formaldehyde to complex A to afford [Rh(H)(CHO)(κ2-dppe)2]+ (B, K1). Coordination of ethene occurs through partial dissociation of one phosphorus atom of the diphosphine ligand, generating [Rh(H)(alkene)(CHO)(κ2-dppe)(κ1-dppe)]+ (IB, K2), followed by the transfer of the hydride to the alkene to give [Rh(alkyl)(CHO)(κ2-dppe)2]+ (C, k3), which is considered the rate-determining step of the process. The cycle is completed by reductive elimination of propanal, thereby regenerating A. The overall activation energy calculated by DFT (Ea = 20.0 kcal mol−1) is in good agreement with the experimental values determined for 1-hexene and styrene (20.1 and 22.9 kcal mol−1, respectively). On the basis of these experimental and DFT results, a mathematical kinetic model with the canonical form r0=K1K2k3RhoalkeneCH2O/(1+K1CH2O) was developed and fitted using a tandem LMFit/Bayesian approach, allowing the values of K1 and K2k3 to be estimated, with comparatively low uncertainty. Overall, this integrated kinetic, computational, and statistical study provides a consistent mechanistic and quantitative framework for understanding the transfer hydroformylation of alkenes with formaldehyde.

Catalysts doi: 10.3390/catal16060520

Authors: Zhihao Chen Jiaxuan Zuo Daimei Chen Yilei Li Guofang Du

Carbamazepine (CBZ), a poorly biodegradable antibiotic, is widely detected in aquatic environments, posing potential threats to ecosystems and human health. There is an urgent need to develop efficient water treatment technologies. This study successfully prepared nitrogen-doped biochar composite materials loaded with zero-valent iron (Fe0@CN) via a one-pot calcination method for activating peroxymonosulfate (PMS) to degrade CBZ. The material was systematically characterized using multiple analytical techniques. Results indicate that Fe0@CN-1.5 exhibits a high specific surface area (482.65 m2/g) and an abundant mesoporous structure, with nitrogen doping promoting graphitic structure formation and the uniform dispersion of zero-valent iron. Under conditions of a 0.3 g/L catalyst loading, a 15 mM PMS concentration, and an initial pH of 5.5, 30 mg/L of CBZ achieved 97% degradation within 30 min. Radical quenching experiments and electrochemical analysis indicate that ·SO4− and ·OH are the primary active species in this system, alongside non-radical electron transfer processes. The material demonstrates excellent degradation performance and cycling stability across various real-world water bodies and pollutant systems. This study provides a carbon-based catalytic material with application potential and a theoretical basis for the efficient treatment of antibiotic wastewater.

Catalysts doi: 10.3390/catal16060519

Authors: Mengyin Chen Rongwei Shi Ziyun Chen Rui Cai Yubing Liu Yining Fan Bolian Xu

Catalytic oxidation has become a crucial technology for removing CO from industrial flue gas. However, the complex composition of flue gas (including NH3, NO, SO2, H2O, etc.) poses significant challenges to the catalytic activity and stability of catalysts. In this work, we propose a new strategy for constructing highly efficient catalysts by loading a Pd component onto TiO2 nanosheets (NSs) with predominantly exposed {001} facets. It has been revealed that the well-connected channels, abundant oxygen vacancies and Ti3+ species on the TiO2(NS) support facilitate the formation of highly dispersed and electron-rich Pd nanoparticles. The weak adsorption of impurities such as NH3, SO2, NO and H2O on these active sites promotes the adsorption and activation of the target reactants (CO and O2), thereby enhancing catalytic activity. Furthermore, such reduced adsorption inhibits the aggregation of Pd nanoparticles and synergizes with the intrinsically weak NH3 adsorption of TiO2(NS) to suppress ammonium sulfate species deposition, thereby enhancing long-term catalytic stability. This work advances TiO2 facet engineering in catalysis and offers new design concepts for efficient CO oxidation catalysts in complex atmospheres.

Catalysts doi: 10.3390/catal16060518

Authors: Jiaqi Fu Yi Li Yuxiang Xu Peilan Ma Fengcai Li Yonggang Sun Song Chen

Adiponitrile (ADN) serves as a critical intermediate for manufacturing polyamide 66. Electrochemical hydrodimerization of acrylonitrile (AN) offers a green and sustainable route for ADN production, yet conventional lead plate cathodes still suffer from high cell voltage, insufficient mechanical stability, and lead dust shedding during long-term operation. In this work, we developed a novel composite lead electrode in ambient air to overcome these drawbacks. Key preparation parameters, including calcination temperature, polytetrafluoroethylene (PTFE) content, substrate type, dispersion method, and dispersant dosage, were carefully screened and optimized. The optimal conditions were determined as follows: PTFE mesh as the substrate, 10% PTFE relative to lead powder, mechanical stirring dispersion, 0.5 wt% sodium hexametaphosphate as dispersant, air calcination at 325 °C, and subsequent electrochemical reduction. SEM, XRD, and XPS characterizations showed that the optimized electrode features a three-dimensional porous network assembled from interlaced rod-like and flower-like micro/nanostructures, which greatly elevates the specific surface area, enriches active sites, and facilitates electrolyte penetration and mass transport. After electrochemical reduction, the electrode surface was dominated by catalytically active Pb0. Electrochemical tests indicated that the composite electrode delivered a current density of 60–70 mA·cm−2 at −1.6 to −2.0 V (vs. SCE) for AN reduction, nearly three times higher than that of a conventional lead plate. In addition, the composite electrode showed improved mechanical hardness and completely suppressed lead dust shedding, greatly enhancing operational safety and service life. Stable voltage was maintained during long-term electrolysis. This study provides a low-cost and scalable strategy for fabricating high-performance lead-based composite cathodes, which can support the industrial-scale green electrosynthesis of adiponitrile from acrylonitrile.

Catalysts doi: 10.3390/catal16060517

Authors: Shengjie Zhu Xiaomin Zhang Lei Dong Yangyang Yuan Xiuyun Ma Lei Xu

Micron-sized plate-like TS-1 zeolites are designed to combine the mass transfer efficiency of MFI straight channels along the b-axis by maximizing the exposure of these channel openings on the a-c crystal surface with the recoverability advantage of micrometer-scale crystals. In this study, micron-sized plate-like TS-1 was successfully synthesized by introducing sodium persulfate (Na2S2O8) as an inorganic morphology-regulating additive. Through comparative experiments with ammonium persulfate, potassium persulfate, sodium carbonate, and sodium sulfate, the regulatory role of persulfate anion (S2O82−), rather than the sodium cation, was identified. By varying the Na2S2O8/SiO2 molar ratio from 0.03 to 0.07, plate-like crystals with a- and c-axis dimensions in the micrometer range and b-axis thickness of 400–1100 nm were obtained. This morphology-regulation strategy was shown to be universal in both steam-assisted crystallization (SAC) and hydrothermal synthesis methods. Furthermore, post-treatment with tetrapropylammonium hydroxide (TPAOH) was applied to introduce additional textural porosity and construct a hierarchical pore structure. The optimized sample (TS-1-0.06SP-HT-P) achieved a total surface area of 444 m2 g−1 and a pore volume of 0.28 cm3 g−1. The catalytic performance of the hierarchically porous samples was evaluated using 1-hexene epoxidation and phenol hydroxylation as model reactions. Catalytic stability tests using phenol hydroxylation (cat. 300 mg, phenol 36 mmol, n(phenol):n(H2O2) = 2, H2O 4 mL, 353 K, 1 h) showed that TS-1-0.06SP-HT-P maintained stable performance over five consecutive cycles, with phenol conversion remaining at 20.8–22.3% and hydroquinone plus catechol selectivity at 73.0–78.1%. This work provides a feasible approach for the plate-like morphology regulation and performance optimization of TS-1 zeolites.

Catalysts doi: 10.3390/catal16060516

Authors: Yuliya Maksimova Aleksandra Pankova Aleksandr Maksimov

The use of hydrolytic enzymes is one of the most promising methods for combating bacterial biofilms. However, the use of native enzymes is limited by the rapid loss of activity under unfavorable conditions. Immobilization of enzymes on carbon nanoparticles enhances their stability, allows for biocatalyst reuse, and creates a synergistic effect due to the intrinsic antimicrobial properties of the nanomaterials. The aim of this investigation was to create and comparatively analyze conjugates of acid and alkaline proteases with carboxylated multiwalled carbon nanotubes (MWCNTs-COOH) and to assess their effect on the formation and destruction of E. coli VKM B-3858D biofilms. The immobilization efficiency and kinetics of enzyme adsorption on the support were quantified by determining the protein concentration using the Bradford assay. The morphology and dispersion of the resulting conjugates were analyzed using atomic force microscopy (AFM). Protease activity was determined by a modified Anson method using the Folin–Ciocalteu reagent. Biofilm biomass was determined using crystal violet staining. The binding efficiency of the acid protease to MWCNTs-COOH was shown to reach 93%, which is significantly higher than that of the alkaline protease. The highest degree of immobilization was observed at a protein concentration of 117–338 μg/mL (10–20 mg/mL of the enzyme preparations). The interaction of the acid protease with the carbon nanoparticles increased dispersion, reducing the size of aggregates from ~1 μm to ~68 nm. As a result, acid protease conjugates with MWCNTs-COOH significantly reduced the biofilm biomass compared to both the enzyme-free control and the native enzyme. Alkaline protease, unlike the acid protease, destroys mature biofilms, and immobilization on MWCNTs-COOH enhances this ability. Native alkaline protease and acid protease conjugates with MWCNTs-COOH are effective in combating the biofilm formation of Gram-negative bacteria, while alkaline protease conjugates are suitable for disrupting mature biofilms.

Catalysts doi: 10.3390/catal16060515

Authors: Sijie He Zilin Zhou Junbo Wang Qi Tang Yin Zhang Jingze Liu Zixuan Zhang Lei Fu Yang Wang

The electrochemical co-conversion of CO2 and H2O into valuable products is a promising approach toward carbon-neutral energy systems. Alloy exsolution from perovskite lattices has emerged as an effective strategy to engineer catalytic interfaces, yet the mechanistic influence of exsolved bimetallic species on CO2/H2O co-electrolysis remains insufficiently clarified. To address this gap, density functional theory (DFT) calculations were performed in this study to systematically examine how NiFe alloy clusters exsolved from the LSFNO (La0.7Sr0.3Fe0.9Ni0.1O3-δ) (111) surface modify the electronic structure of the interfacial region and promote the RWGS reaction in CO2/H2O co-electrolysis. Our work highlights bimetallic alloy exsolution as a powerful strategy for improving co-electrolysis catalysts and offers valuable guidance for the rational design of next-generation high-entropy oxide systems.

Catalysts doi: 10.3390/catal16060514

Authors: Jingwen Huang Junlei Wang He Guo

Efficient utilization of carbon dioxide (CO2) is a critical route toward carbon cycling and low-carbon energy systems. Compared with conventional thermocatalysis, photocatalysis, and electrocatalysis, plasma catalysis can activate CO2 under relatively mild conditions through high-energy electrons, vibrationally excited molecules, radicals, and other reactive species, while catalytic surfaces can redirect reaction pathways and improve selectivity. Rather than only compiling reported performances, this review critically evaluates plasma-catalytic CO2-to-energy conversion from three perspectives: reliable mechanistic knowledge, unresolved uncertainties in plasma–catalyst synergy, and the practical credibility of reactor–catalyst combinations. The fundamentals of non-thermal plasma, CO2 activation, key metrics, plasma–catalyst coupling, and catalyst/reactor/operation factors are first clarified. Representative advances in CO2 splitting, CO2 hydrogenation, dry reforming, and CO2–H2O co-conversion are then compared with attention to energy input, selectivity, power determination, and data comparability. Finally, the key barriers to industrial deployment are discussed, including low energy efficiency, long-term catalyst stability under plasma exposure, uncertain absorbed-power measurement, incomplete carbon/oxygen balances, scale-up of filamentary discharges, and the lack of standardized reporting protocols. This review aims to provide a critical reference for mechanism-guided catalyst design, reactor engineering, and realistic process assessment in plasma-catalytic CO2 utilization.

Catalysts doi: 10.3390/catal16060513

Authors: Hossam A. Nabwey Maha A. Tony

Beauty salon wastewater is an emerging commercial greywater characterized by high chemical oxygen demand (COD), intense color, and low biodegradability due to the presence of surfactants and oxidative dye precursors. This study evaluated a solar-assisted photo-Fenton process using waste-derived iron sludge as a heterogeneous catalyst for treating real beauty salon effluent. Operational parameters, including pH, H2O2 concentration, iron sludge dosage, reaction time, and temperature, were optimized based on dye removal and COD reduction. Under optimal conditions (pH = 3, H2O2 = 400 mg L−1, iron sludge = 40 mg L−1), the system achieved approximately 98% dye removal and 95% COD reduction within 50 min of irradiation. Additionally, maximum performance was observed at 40 °C, while higher temperatures reduced efficiency due to non-productive H2O2 decomposition. Kinetic analysis was performed, and the results indicated predominant second-order behavior. Thermodynamic evaluation confirmed an endothermic process with moderate activation energy (Eₐ = 21.8 kJ mol−1). Response surface methodology confirmed strong parameter interactions and high predictive accuracy. The integration of solar irradiation with iron sludge valorization provides a sustainable and decentralized solution for treating dye-loaded beauty salon wastewater.

Catalysts doi: 10.3390/catal16060512

Authors: Xinlu Xiong Donglin Song Qiang Ren Xu Xiang Jiongliang Yuan

The electrocatalytic reduction in N2 and CO2 into urea under ambient conditions provides a promising strategy for sustainable nitrogen fixation and carbon utilization. However, the low activity and poor selectivity toward urea limit its practical application. Herein, a dual-ligand Cu-based metal–organic framework (Cu-BTC/NH2BDC) was constructed via ligand engineering strategy. The introduction of 2-NH2BDC modulated the electronic structure of Cu sites, generating electron-enriched Cu centers that facilitate CO2 activation, while the hydrogen bonding interaction between the amino and carboxyl groups promotes the activation of N2. As a result, the optimized Cu-BTC/NH2BDC catalyst achieved a urea yield of 6.59 mmol g−1 h−1 with a Faradaic efficiency of 22.85% at −0.2 V versus reversible hydrogen electrode (vs. RHE), outperforming single-ligand counterparts. In situ Raman spectroscopy measurement revealed enhanced the formation of *CO, *NN, and C-N intermediates, indicating improved C-N coupling efficiency. This work provides a feasible strategy for regulating active sites in MOF-based catalysts toward efficient urea electrosynthesis.

Catalysts doi: 10.3390/catal16060511

Authors: Fan Zhang Xuejin Zhang Lezhao Liu Zhi Wang

The present work establishes a sustainable and environmentally benign biocatalytic strategy for the construction of multisubstituted cyanopyrazoles via [3+2] cycloaddition, employing lipase as a highly efficient and practical catalyst. Under the optimized mild reaction conditions, this protocol enables the preparation of structurally diverse cyanopyrazole derivatives with high to excellent isolated yields. The substrate used in this method is the in situ-generated diazoacetonitrile. The corresponding conversion was carried out under mild aqueous conditions, avoiding the flammable and explosive characteristics of diazoacetonitrile. The established protocol exhibits a representative substrate scope and good functional group compatibility. Molecular docking was employed to investigate the reaction, highlighting the significant impact of the active-site architecture of the lipase on this reaction. This biocatalytic approach not only enriches the synthetic toolbox for the preparation of valuable cyanopyrazole scaffolds but also highlights the potential of lipase-catalyzed promiscuous reactions in the green synthesis of pharmaceutically relevant heterocyclic compounds.

Catalysts doi: 10.3390/catal16060510

Authors: Ratheeshkumar Shanmugam Arul Chan Basha Vinod Kumar Saravanan Ramiah Shanmugam Malinee Sriariyanun Ponnusami Venkatachalam

Lignin is one of the most abundant biopolymers in nature. The major challenge in lignin depolymerization lies in the formation of complex mixtures that require extensive downstream separation. Selective depolymerization strategies aim to overcome this limitation by promoting controlled bond cleavage while suppressing undesired secondary reactions. In this work, a series of rare-earth-free, perovskite-type mixed metal oxides with general compositions ZnxNi1–xTiO3 and CuyNi1–yTiO3 were synthesized and evaluated as heterogeneous catalysts for the base-catalyzed depolymerization of lignin. Among the investigated materials, CuTiO3 exhibited superior catalytic performance, enabling the formation of vanillin as the dominant monomer with high selectivity. The selected catalyst was further characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) surface area analysis. The combined effects of key reaction parameters, including temperature, pressure, lignin-to-catalyst ratio, NaOH concentration, and reaction time, were systematically investigated using response surface methodology (RSM). Under the optimized conditions (154 °C, 0.3 MPa, lignin-to-catalyst ratio of 24.5:1, 10 mL of 0.5 M NaOH, and 12 h reaction time), a monomer yield of 11.5 ± 0.46% with ~81% GC-selectivity toward vanillin was achieved. These findings demonstrate that perovskite-type titanates can serve as robust and reusable catalysts.

Catalysts doi: 10.3390/catal16060509

Authors: Amel Ounnar Hicham Zeghioud Mohammod Hafizur Rahman Amine Aymen Assadi Abdelkrim Bouzaza Lotfi Mouni Fatiha Bentahar

This study investigates the TiO2 photocatalytic degradation of naproxen (NPX), a nonsteroidal anti-inflammatory drug, and spiramycin (SPM), a macrolide antibiotic, in aqueous solution. Experiments were conducted using a closed-loop falling thin-film photoreactor equipped with external UV lamps, with particular focus on the competitive degradation behavior when both pharmaceuticals are present simultaneously. Under optimized conditions such as natural pH, UV light intensity of 38 Wm−2, and a recirculation flow rate of 25 L h−1, the TiO2-UV process achieved near-complete degradation of the parent compound (≥99%) for both compounds, whether treated individually or in combination. The degradation kinetics followed a pseudo-first-order model, consistent with heterogeneous photocatalytic systems at low pollutant concentrations. The apparent pseudo-first-order rate constants (kapp) were 0.025 min−1 for NPX and 0.087 min−1 for SPM in single-component systems. In competitive degradation, kapp ranged from 0.005 to 0.007 min−1 for NPX and from 0.003 to 0.031 min−1 for SPM, highlighting the influence of competitive adsorption and reactive-site interaction during simultaneous treatment. Mineralization efficiency differed between the compounds, reaching up to 67% for SPM and 41% for NPX when treated individually, suggesting the formation of more persistent by-products during naproxen degradation. Under competitive conditions, total mineralization rates ranged from 51% to 67% depending on the SPM/NPX molar ratio.

Catalysts doi: 10.3390/catal16060508

Authors: Jian Gong Qian Dong Xiaomei Peng Yan He Xuemin Cui Leping Liu

Achieving efficient overall water splitting with non-precious metal catalysts remains a significant challenge due to the sluggish kinetics of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, we report a nickel–iron bimetallic doped geopolymer electrocatalyst (Ni0.9Fe0.1-GP) fabricated via a one-step alkali activation method on 316L stainless steel. Structural characterizations reveal that Fe3+ incorporation alters the distribution of Na+ and Ni2+ within the geopolymer network and modulates the Ni electronic structure. Electrochemical measurements show that Ni0.9Fe0.1-GP delivers an HER overpotential of 332.42 mV and an OER overpotential of 227.31 mV at 10 mA cm−2, outperforming Ni-GP and bare 316L SS. The practical operating voltage of Ni0.9Fe0.1-GP is 1.81 V, while the two-electrode electrolyzer delivers a comparable current density at 1.90 V (after accounting for uncompensated system resistances). Long-term stability tests demonstrate the superior durability of Ni0.9Fe0.1-GP during HER, OER, and overall water splitting. Mechanistic studies reveal the dual role of Fe3+: substantially increasing the electrochemical active surface area (ECSA) while modulating the Ni electronic structure, and improving structural stability through strong chemical anchoring within the geopolymer network. This work provides new insights into cost-effective bifunctional electrocatalysts and expands the application of geopolymers as functional catalytic supports for water splitting.

Catalysts doi: 10.3390/catal16060507

Authors: Pichai Soison Chamorn Chawengkijwanich Hugo de Lasa Siriluk Chiarakorn

This study explored the influence of high silver (Ag) loading (5–10 mol%) on the photocatalytic performance of zirconium (Zr) co-doped TiO2 (AZT) with a low Zr content. Although various Ag/Zr ratios have been reported, the effect of high Ag loading combined with low Zr content remains largely unrevealed, particularly in low-temperature synthesis where the role of Zr as a phase inhibitor is less critical. To address this gap, the AZT photocatalyst was fabricated via a solvothermal method combined with organic-free peroxy route. Characterization indicated Zr4+ incorporated into the TiO2 lattice, inducing structural distortions and promoting Ti3+ defect states. Simultaneously, silver existed as ternary Ag species, which functioned as visible light responsive co-catalysts that enhanced light absorption via Surface Plasmon Resonance (SPR) and facilitated efficient charge separation. Photocatalytic performance was evaluated through Methylene Blue (MB) decolorization under household LED lamp. The optimized 7% Ag loaded catalyst achieved 99.4% removal efficiency within 6 h, with a reaction rate ten times higher than the Zr-doped sample. This superior activity was attributed to a p-n heterojunction and the SPR effect, narrowing the optical band gap to 2.60 eV. Radical scavenger experiments confirmed that the process was primarily driven by photogenerated holes.

Catalysts doi: 10.3390/catal16060506

Authors: Zhen Wang Jiangtao Bi Zunmin Li Mengmeng Yu Wenli Ma Wei Zhai Jinsheng Lv Xiangjin Kong

This paper presents a numerical comparative study on the ignition characteristics of straight-channel and U-bend micro catalytic combustors, with particular focus on the role of inlet velocity. A two-dimensional computational fluid dynamics model with coupled gas-phase and surface catalytic reaction kinetics for propane combustion is developed using a fluid simulation program ANSYS Fluent. The catalyst coating (Pt/Al2O3) is modeled as a zero-thickness reaction surface, and the U-bend design features an uncoated recirculating channel to ensure identical catalyst loading between the two configurations. Simulations are conducted over an inlet velocity range of 0.25–8 m/s. Key ignition and combustion metrics including ignition temperature, ignition time, maximum combustion temperature, heterogeneous reaction contribution, and thermal/species field distributions are systematically compared. Results reveal a crossover in relative performance depending on flow regime. At low velocities (≤2 m/s), the straight-channel combustor exhibits lower ignition temperatures; at high velocities (≥4 m/s), the U-bend design achieves superior ignition performance with lower ignition temperatures (e.g., 526 K vs. 555 K at 8 m/s) and higher combustion temperatures (1726 K vs. 1474 K at 8 m/s). However, the straight-channel combustor consistently yields shorter ignition times across all velocities (25.9–108.6 s) compared to the U-bend (52.6–145.2 s). The heterogeneous reaction contribution decreases with increasing inlet velocity for both designs, with the straight-channel maintaining higher values than the U-bend. The U-bend achieves higher maximum temperatures due to enhanced heat recirculation, particularly at high flow rates. The findings suggest that the U-bend configuration is advantageous for high-flow-rate applications requiring low ignition temperatures and high combustion temperatures, whereas the straight-channel design is preferable for rapid cold-start scenarios.

Catalysts doi: 10.3390/catal16060505

Authors: Ruoxi Wu Yangwei Luo Jiahong Yang Peng Xu

A binder-free Co3O4 nanoneedle electrode grown directly on nickel foam (Co3O4@NF) was fabricated by hydrothermal synthesis followed by calcination and evaluated for electrocatalytic nitrate reduction to ammonium. The integrated three-dimensional architecture combines the catalytic activity of Co3O4 with the high conductivity and open porosity of nickel foam, thus exposing abundant active sites, shortening electron-transfer pathways, and facilitating mass transport. Among the electrodes prepared at different calcination temperatures, Co3O4@NF calcined at 400 °C delivered the best performance. Under the optimal conditions of −1.4 V vs. Ag/AgCl, pH 7, and an initial NO3−-N concentration of 50 mg L−1, the electrode achieved 83.4% nitrate removal within 480 min together with 98.7% ammonium selectivity. Electrochemical measurements revealed a markedly enlarged electrochemically active surface area and reduced charge-transfer resistance after Co3O4 loading. Mechanistic analyses via TBA quenching experiments and DFT calculations revealed that both the direct pathway and the hydrogen-assisted indirect pathway were operative, with the indirect pathway being dominant due to its lower free energy barrier while maintaining negligible nitrite accumulation. The electrode also showed good cycling stability and retained high ammonium selectivity in real water matrices. These results demonstrate that binder-free Co3O4 nanoneedles supported on nickel foam constitute a promising cathode architecture for coupling nitrate removal with ammonia recovery.

Catalysts doi: 10.3390/catal16060504

Authors: Lei Li Yanle Li Ziqi Tian

The electrochemical carbon dioxide reduction reaction (CO2RR) offers a promising route to mitigate excessive CO2 emissions while enabling the production of value-added chemicals. However, achieving high catalytic selectivity and activity toward specific products remains a critical challenge. Here, we engineer a confined interfacial environment formed between adjacent copper nanoparticles and systematically investigate its impact on CO2RR performance toward CO production. Our theoretical calculations reveal that the confined space effectively stabilizes the *COOH intermediate, a key species governing the CO2-to-CO conversion pathway. In contrast, this geometric confinement exerts a negligible influence on the adsorption energetics of *H, which is associated with the competing hydrogen evolution reaction (HER). As a consequence, the catalyst exhibits a markedly reduced onset potential for CO2RR, accompanied by enhanced selectivity and catalytic activity toward CO formation. These findings highlight the critical role of nanoscale confinement in modulating reaction energetics and provide a viable strategy for the rational design of highly efficient and selective catalysts for CO2RR.

Catalysts doi: 10.3390/catal16060503

Authors: Yudong Meng Xing Fan Zehui Yu Jianyu Cai

In this study, Pt/N-Mo/TiO2 and Pt/Mo/TiO2 catalysts were prepared by the two-step impregnation method for catalytic CO oxidation, with the obtained Mo/TiO2 pretreated or not with NH3 before Pt loading. The Pt/N-1Mo/TiO2 catalyst exhibited superior catalytic activity compared to Pt/1Mo/TiO2 and Pt/N-xMo/TiO2 (x = 0, 0.5, 2, 3, 5), indicating the essential role of N-modification of Mo/TiO2 with an optimal MoO3 loading. The T90 decreased from 133 °C for Pt/1Mo/TiO2 to 105 °C for Pt/N-1Mo/TiO2 under a feed gas consisting of 8000 ppm CO, 16% O2, 3% H2O and balanced N2. For both Pt/1Mo/TiO2 and Pt/N-1Mo/TiO2 catalysts, the H2O in the feed gas showed promotive effects on CO oxidation, while SO2 caused some deactivation at low temperatures. Under the same feed gas composition (8000 ppm CO, 16% O2, 10% H2O, 50 ppm SO2 and balanced N2) and temperature (185 °C), Pt/N-1Mo/TiO2 demonstrated superior SO2 resistance compared to Pt/1Mo/TiO2. CO conversion on Pt/N-1Mo/TiO2 remained above 99% during a 12-h SO2 resistance test, while that on Pt/1Mo/TiO2 gradually decreased to 26%. Characterization results show that NH3 pretreatment of 1Mo/TiO2 significantly improved the dispersion of Pt and enhanced the dissociation of adsorbed H2O into highly reactive hydroxyl (*OH) species, partially explaining the better activity of Pt/N-1Mo/TiO2 compared with Pt/1Mo/TiO2. H2O might promote CO oxidation by facilitating the formation of easily decomposable bicarbonate and formate intermediates. SO2 impeded the Pt reduction process on Pt/1Mo/TiO2 while it hardly affected that on Pt/N-1Mo/TiO2, explaining their difference in SO2 resistance.

Catalysts doi: 10.3390/catal16060502

Authors: Agnieszka A. Pilarska

This review presents a mechanistically focused overview of the role of conductive materials in promoting direct interspecies electron transfer (DIET) during anaerobic digestion. A central interpretative issue addressed in this review is whether the improved process performance observed after material addition reflects enhanced DIET or overlapping physicochemical and biological effects. The review systematises the current state of knowledge on the relationships between material properties, the structure of anaerobic consortia, process response, and the strength of evidence supporting DIET involvement. It discusses indirect and direct electron transfer and the criteria used to interpret the process, microbiological, electrochemical, structural, and molecular data. It also addresses functional interactions at the material–microorganism interface and non-DIET pathways of process improvement, including biomass immobilisation, inhibitor adsorption, buffering, micronutrient effects, and biofilm reorganisation. Conductive materials are also systematised into carbon-based, iron-based, composite and engineered, and organic conductive groups, with their roles related to process limitations, practical constraints, and their applicability in reactor-oriented systems. The distinctive contribution of this review lies in moving beyond simple cataloguing of materials and technological effects towards a framework for mechanistic evaluation, evidence grading, and process translation in conductive-material-assisted anaerobic digestion.

Catalysts doi: 10.3390/catal16060501

Authors: Zhengyu Li Chaoya Han Wenqian Dang Chao Yao Xiazhang Li

Volatile organic compounds (VOCs) represent a significant threat to both environmental quality and public health, driving the need for efficient abatement technologies. Herein, a series of PdCu dual single-atom catalysts supported on peroxide-modified attapulgite (ATP) were synthesized via a microwave-assisted solvothermal approach, and the effect of the Pd/Cu ratio on the catalytic oxidation of toluene was investigated. Results showed that the Pd1Cu1/ATP catalyst exhibited exceptional catalytic performance, achieving 99% toluene conversion at 240 °C under a high weight hourly space velocity of 20,000 mL·g−1·h−1. This high efficiency is attributed to the modification of ATP with hydrogen peroxide solution, which exposes abundant Si-OH, facilitating the immobilization of atomically dispersed atoms and enhancing the adsorption of toluene molecules. In addition, the strong metal–support interaction between the PdCu dual atoms and the ATP support significantly lowers the energy barrier of the reaction, thereby enhancing the low-temperature catalytic activity. In situ DRIFTS further elucidated the reaction pathway and intermediate evolution during toluene oxidation. This work offers an effective strategy for designing highly efficient dual single-atom catalysts for VOCs removal.

Catalysts doi: 10.3390/catal16060500

Authors: Zhishun Wei Yuqi Xu Fitri Rizki Amalia Xi Peng Jiajie Sun Sha Chen Guoqiang Yi Ying Chang Shuaizhi Zheng Ewa Kowalska

In this study, polyhedral self-assembled spherical titania (TS) photocatalyst was successfully synthesized via a one-step hydrothermal method from titanium chloride, sodium dodecyl sulfate and sulfuric acid. Titania modification with iron was carried out through the same procedure by the addition of different amounts of iron(III) chloride to the substrate mixture. Various methods were applied for sample characterization, e.g., XRD, SEM, TEM, XPS, UV-vis DRS, and photo-electrochemical measurements, such as EIS, CV, transient photocurrent, whereas photocatalytic activity was investigated for hydrogen evolution under UV/vis and oxidative decomposition of antibiotics under UV and/or vis, including also tests with scavengers. It has been found that iron was both incorporated in the titania structure (doping) and adsorbed on its surface. Although iron presence has hardly influenced the properties (slight changes in morphology, bandgap energy, and crystallite size), the photocatalytic activity has increased significantly. Therefore, it is proposed that iron might work as an electron sink, hindering the charge carriers’ recombination. Linear evolution of hydrogen, recycling experiments and characterization of samples after recycling have confirmed a good stability of iron-modified titania.

Catalysts doi: 10.3390/catal16060499

Authors: Somayeh Ostovar Daily Rodríguez-Padrón Farveh Saberi Alina M. Balu Rafael Luque

In the original publication [...]

Catalysts doi: 10.3390/catal16060498

Authors: Mengfan Niu Rongxin Lin Baiqing Li Qinqin Liu Guoting Xu Mengyao Xiong Mei Du Shuai Yuan Abdukader Abdukayum

Photocatalytic water splitting for hydrogen (H2) evolution is a critical sustainable energy strategy, and cadmium sulfide (CdS) is a promising visible-light photocatalyst due to its suitable band gap. However, the practical application of pure CdS is severely hindered by rapid charge-carrier recombination and significant photocorrosion. In this work, we constructed a CdS/vanadium carbide (VC) photocatalyst via a simple ultrasonic method. The structural, morphological, optical, and photoelectrochemical properties of the composites were systematically investigated. Under visible light (λ ≥ 420 nm) and with 0.35 M Na2S-0.25 M Na2SO3 as the sacrificial agent, the optimized composite featuring a CdS:VC mass ratio of 10:1 (denoted CV-10) achieved a remarkable hydrogen evolution rate of 3485.6 μmol g−1 h−1. This rate represents a 60-fold enhancement over pure-phase CdS and significantly surpasses that of a conventional Pt/CdS catalyst. Furthermore, the CV-10 composite demonstrated excellent stability, showing no activity decay after 16 h of cycling. Spectroscopic and electrochemical analyses revealed that the metallic VC can function as an efficient cocatalyst, accelerating charge separation and transfer while suppressing electron–hole recombination. This work demonstrates that noble-metal-free VC is a highly effective and low-cost cocatalyst, providing a new pathway for designing efficient and stable CdS-based photocatalysts in solar hydrogen production.

Catalysts doi: 10.3390/catal16060497

Authors: Jiaming Wang Honglan Li Junmiao Zhang Changchun Xu Beibei Xiao

Given its high energy density and environmentally benign nature, hydrogen has emerged as a sustainable alternative to conventional fossil fuels. Consequently, water electrolysis has attracted considerable attention as a hydrogen production method, with the design of efficient and durable catalytic materials representing a crucial research focus. Herein, we design a two-dimensional metal–organic framework (MOF) for hydrogen evolution electrocatalysis using density functional theory calculation. V3(C6O6)2, Cr3(C6O6)2 and Co3(C6O6)2 emerge as potentially viable, meeting dual criteria of thermodynamic stability and optimal catalytic activity. Notably, Cr3(C6O6)2 demonstrates unexpectedly high hydrogen evolution reaction (HER) activity comparable to Pt-based catalysts, owing to the moderate H-s/Cr-d-orbital hybridization that fine-tunes H binding. The findings provide substantial theoretical guidance for developing advanced electrocatalysts for sustainable hydrogen evolution.