Catalysts

19 pages, 2845 KiB

Open AccessReview

Nickel Selenides in Electrocatalysis: Coupled Formate and Hydrogen Production Through Methanol Oxidation Reaction

by Hong Tu, Yan Zhong, Zhihao Yang, Caihong Zhang, Yi Ma, Yong Zhang, Ning Jian, Huan Ge and Junshan Li

Catalysts 2025, 15(6), 516; https://doi.org/10.3390/catal15060516 - 23 May 2025

Abstract

The hydrogen economy, associated with electrochemical water splitting, represents a promising pathway to mitigate reliance on fossil fuels. However, the efficiency of this process is constrained by the sluggish oxygen evolution reaction (OER) at the anode, with low commercial interests of the produced [...] Read more.

The hydrogen economy, associated with electrochemical water splitting, represents a promising pathway to mitigate reliance on fossil fuels. However, the efficiency of this process is constrained by the sluggish oxygen evolution reaction (OER) at the anode, with low commercial interests of the produced oxygen. As a promising solution, OER can be replaced with the methanol oxidation reaction (MOR), which not only accelerates the hydrogen evolution reaction (HER) but also yields valuable formate as a product, depending on the nature of the anode electrocatalysts. In this context, nickel selenides have emerged as highly efficient and cost-effective electrocatalysts due to their rich compositional diversity, tunable electronic structures, and superior conductivity. Additionally, nickel selenides exist in multiple stoichiometric and nonstoichiometric phases, and also in the engineering versatility for optimizing catalytic MOR performance. This review comprehensively presents the design principles of electrocatalysts, provides a strategy for the optimization of performance, and discusses the mechanistic understanding of nickel selenide-based electrocatalysts for coupled HER and MOR systems, particularly focusing on the MOR. By bridging fundamental insights with practical applications, it additionally highlights the latest advancements in their catalytic MOR performance, offering insights into their potential for future energy and chemical applications. Full article

(This article belongs to the Special Issue Catalysis for Energy Storage and Batteries)

16 pages, 8392 KiB

Open AccessArticle

Ethanol Dehydration Pathways on NASICON-Type A_0.33M₂(PO₄)₃ ((A = Dy, Y, Yb); M = Ti, Zr) Catalysts: The Role of Hydroxyl Group Proton Mobility in Selectivity Control

by Anna I. Zhukova, Alina D. Sazonova, Andrey N. Kharlanov, Elena A. Asabina, Vladimir I. Pet’kov, Vladislav A. Sedov, Vasiliy D. Prokhin, Diana A. Osaulenko, Yuri A. Fionov, Irina I. Mikhalenko, Elena A. Fionova and Dmitry Yu. Zhukov

Catalysts 2025, 15(6), 515; https://doi.org/10.3390/catal15060515 - 23 May 2025

Abstract

NASICON-type titanium and zirconium phosphates doped with rare-earth cations, A_0.33M₂(PO₄)₃ (M = Ti, Zr; A = Dy, Y, Yb), were synthesized using the sol–gel method and investigated as catalysts for ethanol dehydration at 300–400 °C. The [...] Read more.

NASICON-type titanium and zirconium phosphates doped with rare-earth cations, A_0.33M₂(PO₄)₃ (M = Ti, Zr; A = Dy, Y, Yb), were synthesized using the sol–gel method and investigated as catalysts for ethanol dehydration at 300–400 °C. The catalysts were characterized via XRD, SEM, BET, and FTIR spectroscopy. The relationships between the catalyst composition, acidity and the dehydration activity were evaluated. Diethyl ether (DEE) formation is promoted by the presence of the zirconium phosphates (ZrP), while the presence of titanium phosphate (TiP) catalyzes the formation of both ethylene and diethyl ether (DEE). The application of Fourier-transform infrared (FTIR) spectroscopy to the analysis of adsorbed C₆H₆ has revealed the presence of hydroxyl groups exhibiting varying degrees of proton-donating mobility. This finding has enabled the correlation of the structure of the active sites with the process’s selectivity. The results underscore the key function of OH-group localization and framework geometry in the control of form-selective reactions. Full article

(This article belongs to the Section Catalysis for Sustainable Energy)

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11 pages, 1825 KiB

Open AccessFeature PaperArticle

Intracellular Lipases for Enzymatic Synthesis of Phenylalanine Butyramide in a Biphasic Reaction System

by Xinyu Fan, Pengcheng Chen, Dan Wu and Pu Zheng

Catalysts 2025, 15(6), 514; https://doi.org/10.3390/catal15060514 - 23 May 2025

Abstract

Phenylalanine butyramide (FBA) is a novel butyric acid derivative with favorable sensory properties, which has broad prospects in medicine and feed processing. However, there is currently limited research on the enzymatic synthesis of FBA. As is well known, lipase plays a crucial role [...] Read more.

Phenylalanine butyramide (FBA) is a novel butyric acid derivative with favorable sensory properties, which has broad prospects in medicine and feed processing. However, there is currently limited research on the enzymatic synthesis of FBA. As is well known, lipase plays a crucial role in amide bond synthesis, but it typically requires completely anhydrous conditions. The lipase from Sphingomonas sp. HXN-200 (SpL) is the only intracellular lipase identified to date, capable of catalyzing the ammonolysis of esters or acids in an aqueous phase. In this study, we developed a method for the synthesis of FBA catalyzed by SpL in a biphasic reaction system of water and n-hexane. SpL was successfully expressed in E. coli BL21, and the optimal induction conditions were 0.4 mM IPTG and 18 h. It was ascertained that the n-hexane system containing 2% water was conducive to the reaction. Under optimized reaction conditions, 0.89 mg/mL of FBA was obtained within 15 h at 30 °C. Additionally, we found that SpL also has the ability to hydrolyze amides in the reaction of SpL catalyzing the formation of amides, so we further analyzed its catalytic mechanism. Full article

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12 pages, 1482 KiB

Open AccessFeature PaperArticle

Design and Optimization of Chromium-Based Polymeric Catalysts for Selective Electrocatalytic Synthesis of Hydrogen Peroxide

by Huiying Meng, Wen Luo, Yang Wu and Yifan Zhang

Catalysts 2025, 15(6), 513; https://doi.org/10.3390/catal15060513 - 23 May 2025

Abstract

In this study, we designed and synthesized a series of chromium-based polymers (Cr-Ps) and their composites using oxidized carbon nanotubes (O-CNTs) through one-pot ligand engineering. The H₂O₂ production capacity of Cr-Ps increased with an increasing ratio of C–O and Cr–O [...] Read more.

In this study, we designed and synthesized a series of chromium-based polymers (Cr-Ps) and their composites using oxidized carbon nanotubes (O-CNTs) through one-pot ligand engineering. The H₂O₂ production capacity of Cr-Ps increased with an increasing ratio of C–O and Cr–O bonds, which is consistent with the trend observed in the Cr-Ps@O-CNT. The addition of O-CNTs during Cr-Ps synthesis led to a dense structure, which enhanced the electron donor effect and effectively improved the selectivity of the materials for the electrocatalytic production of H₂O₂. Furthermore, during the modulation of different ligands, we observed that the polymers and their complexes formed with terephthalic acid ligands containing para-carboxyl groups had the highest coordination activity and selectivity. The Cr-BDC@O-CNT, using terephthalic acid as the ligand, had the highest C–O and Cr–O densities, resulting in an H₂O₂ yield of 87% in an alkaline solution and an electron transfer number of about 2.2. Compared with Cr-BDC without O-CNTs, its selectivity increased by 32%, due to the higher number of C–O and Cr–O bonds in its dense structure. Moreover, the mass activity of the Cr-BDC@O-CNT reached 19.42 A g⁻¹ at 0.2 V and the Faraday efficiency reached up to 94%, demonstrating excellent electroreduction activity. Our work provides insight into the design of efficient H₂O₂ electrocatalysts through ligand engineering, opening up new ideas for future research. Full article

(This article belongs to the Special Issue Powering the Future: Advances of Catalysis in Batteries)

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17 pages, 2309 KiB

Open AccessArticle

Cerium-Doped Titanium Dioxide (CeT) Hybrid Material, Characterization and Spiramycin Antibiotic Photocatalytic Activity

by Hayat Khan

Catalysts 2025, 15(6), 512; https://doi.org/10.3390/catal15060512 - 23 May 2025

Abstract

Recently, aquatic life and human health are seriously threatened by the release of pharmaceutical drugs. For a sustainable ecosystem, emerging contaminants like antibiotics must be removed from drinking water and wastewater. To address this issue pure and cerium-doped titanium dioxide (CeT) nanoparticles were [...] Read more.

Recently, aquatic life and human health are seriously threatened by the release of pharmaceutical drugs. For a sustainable ecosystem, emerging contaminants like antibiotics must be removed from drinking water and wastewater. To address this issue pure and cerium-doped titanium dioxide (CeT) nanoparticles were produced with stable tetragonal (anatase) lattices by room temperature sol–gel method and employing the inorganic titanium oxysulfate (TiOSO₄) as titanium precursor. The structural analysis by X-ray diffraction (XRD) revealed that at calcination temperature of 600 °C all (un and doped) powders were composed of crystalline anatase TiO₂ with the crystallite sizes in the range of 13.5–11.3 nm. UV–vis DRS spectroscopy revealed that the most narrowed bandgap value of 2.75 eV was calculated for the 0.5CeT sample containing the optimum dopant content of 0.5 weight ratio. X-ray spectroscopy (XPS) confirmed the presence of the impurity level Ce³⁺/Ce⁴⁺, which became responsible for the decrease in bandgap as well as for the photoinduced carriers recombination rate. Photocatalytic tests showed that the maximum decomposition of the model spiramycin (SPR) antibiotic pollutant was 88.0% and 77.0%, under UV and visible light, respectively. According to the reaction kinetics, SPR decomposition adhered to the Langmuir–Hinshelwood (L–H) model and via ROS experiments mainly hydroxyl radicals (OH^•) followed by photogenerated holes (h⁺s) become responsible for the pollutant degradation. In summary, this study elaborates on the role of xCeT nanoparticles as an efficient photocatalyst for the elimination of organic contaminants in wastewater. Full article

(This article belongs to the Special Issue Efficient Catalytic Degradation of Organic Pollutants by Nanocomposites)

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3 pages, 348 KiB

Open AccessEditorial

Advancing Sustainable Catalysis: Catalytic Solutions for Green Chemistry and the Energy Transition

by Muhammad Saeed Akhtar and Wajid Zaman

Catalysts 2025, 15(6), 511; https://doi.org/10.3390/catal15060511 - 22 May 2025

Abstract

Sustainable catalysis is crucial in tackling some of the most pressing global challenges we face today, especially the serious threats of climate change, environmental degradation, and the depletion of our natural resources [...] Full article

(This article belongs to the Special Issue Sustainable Catalysis for Green Chemistry and Energy Transition)

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13 pages, 2374 KiB

Open AccessArticle

Preparation of Metal-Hybridized Magnetic Nanocellulose for ω-Transaminase Immobilization

by Jiayao Yang, Xingxing Wang, Hongpeng Wang and Jun Huang

Catalysts 2025, 15(6), 510; https://doi.org/10.3390/catal15060510 - 22 May 2025

Abstract

The enzyme ω-transaminase (ω-TA) has garnered significant attention due to its capacity to catalyze the synthesis of chiral amines with high efficiency. Nevertheless, the lack of stability of ω-TA and the difficulty of recycling and reuse are still challenges that limit its application. [...] Read more.

The enzyme ω-transaminase (ω-TA) has garnered significant attention due to its capacity to catalyze the synthesis of chiral amines with high efficiency. Nevertheless, the lack of stability of ω-TA and the difficulty of recycling and reuse are still challenges that limit its application. This study developed a novel magnetic nanocellulose composite carrier (NNC@Fe₃O₄@Ni), synthesized from microcrystalline cellulose via low-eutectic solvent treatment, amine modification, and metal hybridization. The NNC@Fe₃O₄@Ni was characterized by FTIR, XPS, XRD, BET, and VSM. Additionally, the performance and catalytic behavior of the immobilized enzyme were investigated. The results revealed that NNC@Fe₃O₄@Ni exhibited a high specific surface area, superparamagnetism, and dual-site functionality (amine/Ni²⁺). Response Surface Methodology (RSM) optimized the carrier-enzyme interaction parameters, yielding optimal immobilization conditions: a mass ratio of 50.8 mg g⁻¹, temperature of 12.5 °C, and duration of 58.6 min, achieving 82.91% enzyme activity recovery. Compared to free enzymes, the immobilized variant demonstrated enhanced catalytic stability, with expanded optimal pH (9.0) and temperature (30 °C). Thermal stability assessments showed 84.39% activity retention after 5 h at 30 °C and 90.30% residual activity post-120 h storage. The catalyst maintained >80% efficiency over 10 reuse cycles. These findings confirm the efficacy of magnetic nanocellulose carriers in enhancing ω-TA stability, reusability, and catalytic performance, offering a viable strategy for industrial biocatalytic processes. Full article

(This article belongs to the Special Issue Catalyst Immobilization)

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34 pages, 2339 KiB

Open AccessFeature PaperReview

Process Intensification for CO₂ Hydrogenation to Liquid Fuels

by Simona Renda and Miguel Menéndez

Catalysts 2025, 15(6), 509; https://doi.org/10.3390/catal15060509 - 22 May 2025

Abstract

Liquid fuels obtained from CO₂ and green hydrogen (i.e., e-fuels) are powerful tools for decarbonizing economy. Improvements provided by Process Intensification in the existing conventional reactors aim to decrease energy consumption, increase yield, and ensure more compact and safe processes. This review [...] Read more.

Liquid fuels obtained from CO₂ and green hydrogen (i.e., e-fuels) are powerful tools for decarbonizing economy. Improvements provided by Process Intensification in the existing conventional reactors aim to decrease energy consumption, increase yield, and ensure more compact and safe processes. This review describes the advances in the production of methanol, dimethyl ether, and hydrocarbons by Fischer–Tropsch using different Process Intensification tools, mainly membrane reactors, sorption-enhanced reactors, and structured reactors. Due to the environmental interest, this review article focused on discussing methanol and dimethyl ether synthesis from CO₂ + H₂, which also represented the most innovative approach. The use of syngas (CO + H₂) is generally preferred for the Fischer–Tropsch process; hence, studies examining this process were included in the present review. Both mathematical models and experimental results are discussed. Achievements in the improvement of catalytic reactor performance are described. Experimental results in membrane reactors show increased performance in e-fuels production compared to the conventional packed bed reactor. The combination of sorption and reaction also increases the single-pass conversion and yield, although this improvement is limited by the saturation capacity of the sorbent in most cases. Full article

(This article belongs to the Special Issue Fluidizable Catalysts for Novel Chemical Processes)

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20 pages, 5514 KiB

Open AccessArticle

The Tailored Surface Oxygen Vacancies and Reduced Optical Band Gap of NiO During the Development of NiO@Polyaniline Hybrid Materials for the Efficient Asymmetric and Oxygen Evolution Reaction Applications

by Fida Hussain, Wanhinyal Dars, Rabia Kanwal, Jethanand Parmar, Ghansham Das, Ahmed Raza, Haresh Kumar, Rameez Mangi, Masroor Ali Bhellar, Ambedker Meghwar, Kashif Ali, Aneela Tahira, Muhammad Ali Bhatti, Elmuez Dawi, Rafat M. Ibrahim, Brigitte Vigolo and Zafar Hussain Ibupoto

Catalysts 2025, 15(6), 508; https://doi.org/10.3390/catal15060508 - 22 May 2025

Abstract

This study employed a simple and cost-effective method for developing NiO with reduced optical band gaps that can be combined with nanostructured polyaniline (PANI). The composite systems were used as electrocatalytic and electrode materials in oxygen evolution reactions (OER) and in supercapacitor applications. [...] Read more.

This study employed a simple and cost-effective method for developing NiO with reduced optical band gaps that can be combined with nanostructured polyaniline (PANI). The composite systems were used as electrocatalytic and electrode materials in oxygen evolution reactions (OER) and in supercapacitor applications. We prepared the composite material in two stages: NiO was prepared with a reduced optical band gap by combining it with wheat peel extract. This was followed by the incorporation of PANI nanoparticles during the chemical oxidation polymerization process. A variety of structural characterization techniques were employed, including scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). A surface-modified NiO/PANI composite with enhanced surface area, fast charge transfer rate, and redox properties was produced. When NiO/PANI composites were tested in KOH electrolytic solution, 0.5 mL of wheat peel extract-mediated NiO/PANI demonstrated excellent electrochemical performance. It was found that the asymmetric supercapacitor (ASC) device had the highest specific capacitance of 404 Fg⁻¹ at a current density of 4 Ag⁻¹. In terms of energy density and power density, the ASC device was found to have 140 Whkg⁻¹ and 3160 Wkg⁻¹, respectively. The ASC device demonstrated excellent cycling stability and charge storage rates, with 97.9% capacitance retention and 86.9% columbic efficiency. For the OER process, an overpotential of 320 mV was observed at a current density of 10 mA/cm². It was found that the NiO/PANI composite was highly durable for a period of 30 h. A proposed hypothesis suggested that reducing the optical band gap of NiO and making its composites with PANI could be an appealing approach to developing next-generation electrode materials for supercapacitors, batteries, and fuel cells. Full article

(This article belongs to the Special Issue Advances in Biomass-Based Electrocatalysts)

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4 pages, 149 KiB

Open AccessEditorial

Study on Electrocatalytic Activity of Metal Oxides

by Xiaochao Wu and Zhao Cai

Catalysts 2025, 15(6), 507; https://doi.org/10.3390/catal15060507 - 22 May 2025

Abstract

Electrocatalysis represents a critical branch of catalysis research, characterized by its interdisciplinary nature and drawing interest from chemists, physicists, biochemists, surface scientists, materials scientists, and engineers [...] Full article

(This article belongs to the Special Issue Study on Electrocatalytic Activity of Metal Oxides)

20 pages, 1850 KiB

Open AccessArticle

Biosynthesis of Fe₃O₄ Nanoparticles Using Egg Albumin: Antifungal, Dielectric Analysis and Photocatalytic Activity

by Azam Raza, Sally Mostafa Khadrawy, Irfan Ahmad, Mohd Imran, Gulrana Khuwaja, Humaira Parveen, Sayeed Mukhtar, Bhagyashree R. Patil, Ahmed A. Allam, Hassan A. Rudayni, Syed Kashif Ali and Absar Ahmad

Catalysts 2025, 15(6), 505; https://doi.org/10.3390/catal15060505 - 22 May 2025

Abstract

The use of chemical pesticides has led to adverse effects on human health and the environment, prompting the exploration of alternative solutions. This study successfully biosynthesized iron oxide nanoparticles (Fe₃O₄ NPs) using chicken egg albumin, which served as reducing and [...] Read more.

The use of chemical pesticides has led to adverse effects on human health and the environment, prompting the exploration of alternative solutions. This study successfully biosynthesized iron oxide nanoparticles (Fe₃O₄ NPs) using chicken egg albumin, which served as reducing and capping agents, and evaluated their antifungal efficacy against Macrophomina phaseolina. The fungicidal potential of Fe₃O₄ NPs was assessed in vitro, demonstrating enhanced inhibition of M. phaseolina’s radial growth with increasing concentrations from 100 ppm to 300 ppm. Dielectric properties were also studied, revealing advantageous current conduction processes and conductive network development with temperature variation, which is particularly beneficial in the low-frequency range. At a fixed pH, dielectric studies showed increased mobile carrier movement and polarization with rising temperature at a fixed frequency. The photocatalytic activity of Fe₃O₄ NPs was assessed for the degradation of methylene blue (MB), an organic dye, under solar irradiation. In this study, Fe₃O₄ NPs photocatalysts achieved 89% (MB) degradation within 75 min. This research underscores the potential of using chicken egg albumin for the biosynthesis of Fe₃O₄ NPs. It offers a promising alternative for plant disease control and highlights their suitability for integration into eco-friendly plant protection strategies. Full article

(This article belongs to the Special Issue Catalytic Materials for Hazardous Wastewater Treatment)

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16 pages, 2543 KiB

Open AccessArticle

Enhancing Propane Dehydrogenation Performance on Cerium-Modified PtSnIn/Al Trimetallic Catalysts

by Jinbao Liu, Ke Xia and Fen Zhang

Catalysts 2025, 15(5), 506; https://doi.org/10.3390/catal15050506 - 21 May 2025

Abstract

The effects of Ce incorporation into trimetallic PtSnIn-supported catalysts were investigated for a propane dehydrogenation reaction with advanced characterization techniques. It was found that some Ce species exist in the form of CeAlO₃ on the reduced PtSnIn/xCe-Al catalyst, significantly enhancing [...] Read more.

The effects of Ce incorporation into trimetallic PtSnIn-supported catalysts were investigated for a propane dehydrogenation reaction with advanced characterization techniques. It was found that some Ce species exist in the form of CeAlO₃ on the reduced PtSnIn/xCe-Al catalyst, significantly enhancing the thermal stability of the alumina support. The NH₃-TPD measurements verified that the total acidity of the PtSnIn/xCe-Al catalysts decreases with the addition of Ce. The PtSnIn/1.5Ce-Al catalyst exhibits the optimal particle distribution with the smallest Pt particle size of 8.0 nm, which was revealed by TEM. The H₂-TPR and XPS results suggest that more oxidized-state Sn species form on catalyst surfaces, and the metal–support interaction can be strengthened when Ce is introduced. Furthermore, TG analysis demonstrates that Ce incorporation substantially reduces coke formation on the spent catalysts. The PtSnIn/1.5Ce-Al catalyst exhibits exceptional catalytic performance, achieving an initial propane conversion of 62.6% and maintaining a conversion of 57.2% after a 120 min reaction. In addition, the PtSnIn/1.5Ce-Al catalyst possesses high long-term stability. Over 40.0% propane conversion can be maintained after a 53 h continuous PDH reaction. These findings highlight the pivotal role of Ce in improving the structural properties and catalytic performance of PtSnIn-based catalysts for propane dehydrogenation, offering valuable insights for the design of highly efficient and stable dehydrogenation catalysts. Full article

(This article belongs to the Special Issue Catalytic Removal of Volatile Organic Compounds (VOCs))

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10 pages, 2488 KiB

Open AccessArticle

Photothermal-Assisted Photocatalytic Degradation of Antibiotic by Black g-C3N4 Materials Derived from C/N Precursors and Tetrachlorofluorescein

by Xiyuan Gao, Pengnian Shan, Weilong Shi and Feng Guo

Catalysts 2025, 15(5), 504; https://doi.org/10.3390/catal15050504 - 21 May 2025

Abstract

The development of photothermal-assisted photocatalytic systems with broad-spectrum solar utilization and high charge separation efficiency remains a critical challenge for antibiotic degradation. Herein, we report novel black g-C₃N₄ (BCN) materials synthesized via a one-step thermal copolymerization strategy using C/N precursors [...] Read more.

The development of photothermal-assisted photocatalytic systems with broad-spectrum solar utilization and high charge separation efficiency remains a critical challenge for antibiotic degradation. Herein, we report novel black g-C₃N₄ (BCN) materials synthesized via a one-step thermal copolymerization strategy using C/N precursors and tetrachlorofluorescein. After the introduction of tetrachlorofluorescein, the color of the sample changes, which gives BCN enhanced light absorption and a significant photothermal effect for poorly heating-assisted photocatalysis. The synergistic coupling of photothermal and photocatalytic processes enabled the optimal BCN-U sample to achieve exceptional degradation efficiency (89% within 120 min) for a typical antibiotic (e.g., tetracycline) under an LED lamp as the visible light source, outperforming conventional yellow g-C₃N₄ (YCN-U) by a factor of 1.37. Mechanistic studies revealed that the photothermal effect facilitates carrier separation via thermal-driven electron excitation while accelerating reactive oxygen species (•OH and •O₂⁻) generation. The synergistic interplay between photocatalysis and photothermal effects, which improved mass transfer, ensures robust stability, which provides new insights into designing dual-functional carbon nitride-based materials for sustainable environmental remediation. Full article

(This article belongs to the Special Issue Advances in Photocatalytic Degradation of Pollutants in Wastewater)

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14 pages, 5171 KiB

Open AccessArticle

Cobalt-Decorated Carbonized Wood as an Efficient Electrocatalyst for Water Splitting

by Zichen Cheng, Zekun Li, Shou Huang, Junfan Pan, Jiaxian Mei, Siqi Zhang, Xingyu Peng, Wen Lu and Lei Yan

Catalysts 2025, 15(5), 503; https://doi.org/10.3390/catal15050503 - 21 May 2025

Abstract

The efficient mass transport and enhanced accessibility of active sites are crucial for high-performance electrocatalysts in water splitting. Inspired by the hierarchical structure of natural wood, we engineered a monolithic electrocatalyst, cobalt nanoparticles encapsulated in nitrogen-doped carbon layers on carbonized wood (Co@NC/CW), by [...] Read more.

The efficient mass transport and enhanced accessibility of active sites are crucial for high-performance electrocatalysts in water splitting. Inspired by the hierarchical structure of natural wood, we engineered a monolithic electrocatalyst, cobalt nanoparticles encapsulated in nitrogen-doped carbon layers on carbonized wood (Co@NC/CW), by carbonizing wood to create a three-dimensional framework with vertically aligned macropores. The unique architecture encapsulates cobalt nanoparticles within in situ-grown nitrogen-doped graphene layers on wood-derived microchannels, facilitating ultrafast electrolyte infusion and anisotropic electron transport. As a result, the optimized freestanding Co@NC/CW electrode exhibits remarkable bifunctional activity, achieving overpotentials of 403 mV and 227 mV for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, at a current density of 50 mA cm⁻². Furthermore, the integrated hybrid electrolyzer combining the HER and the OER delivers an impressive 50 A cm⁻² at a cell voltage of 1.72 V while maintaining a Faradaic efficiency near 99.5% and sustaining long-term stability over 120 h of continuous operation. Co@NC/CW also demonstrates performance in the complete decomposition of alkaline seawater, underscoring its potential for scalable applications. This wood-derived catalyst design not only leverages the natural hierarchical porosity of wood but also offers a sustainable platform for advanced electrochemical systems. Full article

(This article belongs to the Special Issue Recent Progress on Electrocatalytic Hydrogen Evolution Reaction)

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18 pages, 1751 KiB

Open AccessArticle

Natural Pyrolusite-Catalyzed Ozonation for Nanoplastics Degradation

by Victor Mello, Julia Nieto-Sandoval, Márcia Dezotti and Carmen Sans

Catalysts 2025, 15(5), 502; https://doi.org/10.3390/catal15050502 - 21 May 2025

Abstract

The increasing prevalence of polystyrene nanoplastics (PSNPs) in aquatic environments poses significant risks due to their persistence and potential toxicity. Conventional water treatment methods have proven ineffective in removing these emerging pollutants, highlighting the urgent need for sustainable and efficient treatment. This study [...] Read more.

The increasing prevalence of polystyrene nanoplastics (PSNPs) in aquatic environments poses significant risks due to their persistence and potential toxicity. Conventional water treatment methods have proven ineffective in removing these emerging pollutants, highlighting the urgent need for sustainable and efficient treatment. This study investigates the application of catalytic ozonation using natural pyrolusite (n-MnO₂) and oxalic acid (OA) as a co-catalyst for the environmentally friendly degradation of PSNPs. Key operational parameters, including pH, applied ozone dose, pyrolusite dosage, and OA concentration, were systematically evaluated. Results demonstrate that the MnO₂ + OA + O₃ system enhances the generation of reactive oxygen species (ROS), leading to improved PSNP removal while maintaining the applied ozone dose compared to the single ozonation reaction. The highest TOC removal of 75% was achieved within 30 min of treatment under optimal conditions (pH = 4, [MnO₂] = 0.5 g L⁻¹, [OA] = 10 mg L⁻¹, and ozone dose of 37.5 mg min⁻¹), with significant turbidity reduction, indicating both chemical and physical degradation of PSNPs. Catalyst reusability after three consecutive cycles confirmed minimal loss in activity, reinforcing its potential as a sustainable catalytic system. These findings highlight natural MnO₂-driven catalytic ozonation as a green and effective strategy for nanoplastic removal in water treatment applications. Full article

(This article belongs to the Special Issue Environmentally Friendly Catalysts for Energy and Water Treatment Applications)

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22 pages, 6961 KiB

Open AccessArticle

Support Effects on Fe- or Cu-Promoted Ni Catalysts Used in the Catalytic Deoxygenation of Tristearin to Fuel-like Hydrocarbons

by Great C. Umenweke, Robert Pace, Thomas Récalt, Olivier Heintz, Gilles Caboche and Eduardo Santillan-Jimenez

Catalysts 2025, 15(5), 501; https://doi.org/10.3390/catal15050501 - 21 May 2025

Abstract

Previous studies have shown that fats, oils, and greases (FOG) can be deoxygenated to fuel-like hydrocarbons over inexpensive alumina-supported Ni catalysts promoted with Cu or Fe to afford excellent yields of renewable diesel (RD). In this study, supports other than alumina—namely, SiO₂ [...] Read more.

Previous studies have shown that fats, oils, and greases (FOG) can be deoxygenated to fuel-like hydrocarbons over inexpensive alumina-supported Ni catalysts promoted with Cu or Fe to afford excellent yields of renewable diesel (RD). In this study, supports other than alumina—namely, SiO₂-Al₂O₃, Ce_0.8Pr_0.2O₂, and ZrO₂—were investigated to develop catalysts showing improved RD yields and resistance to coke-induced deactivation relative to Al₂O₃-supported catalysts. Results showed that catalysts supported on Ce_0.8Pr_0.2O₂ and ZrO₂ outperformed SiO₂-Al₂O₃-supported formulations, with 20%Ni-5%Fe/ZrO₂ affording a quantitative yield of diesel-like hydrocarbons. Notably, the abundance of weak acid sites varied considerably across the different supports, and a moderate concentration of these sites corresponded with the best results. Additionally, temperature-programmed reduction measurements revealed that Ni reduction is greatly dependent on both the identity of the promoter and catalyst support, which can also be invoked to explain catalyst performance since metallic Ni is identified as the likely active site for the deoxygenation reaction. It was also observed that Ce_0.8Pr_0.2O₂ provides high oxygen storage capacity and oxygen mobility/accessibility, which also improves catalyst activity. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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23 pages, 3490 KiB

Open AccessReview

Rational Design Strategies for Covalent Organic Frameworks Toward Efficient Electrocatalytic Hydrogen Peroxide Production

by Yingjie Zheng, Yi Zhao, Wen Luo, Yifan Zhang, Yong Wang and Yang Wu

Catalysts 2025, 15(5), 500; https://doi.org/10.3390/catal15050500 - 21 May 2025

Abstract

Hydrogen peroxide (H₂O₂) is a versatile and environmentally friendly oxidant with broad applications in industry, energy, and environmental remediation. Electrocatalytic H₂O₂ production via the two-electron oxygen reduction reaction (2e⁻ ORR) has emerged as a sustainable [...] Read more.

Hydrogen peroxide (H₂O₂) is a versatile and environmentally friendly oxidant with broad applications in industry, energy, and environmental remediation. Electrocatalytic H₂O₂ production via the two-electron oxygen reduction reaction (2e⁻ ORR) has emerged as a sustainable alternative to traditional anthraquinone processes. Covalent organic frameworks (COFs), as a class of crystalline porous materials, exhibit high structural tunability, large surface areas, and chemical stability, making them promising electrocatalysts for 2e⁻ ORR. This review systematically summarizes recent advances in COF-based electrocatalysts for H₂O₂ production, including both metal-free and metal-containing systems. We discuss key strategies in COF design—such as dimensional modulation, linkage engineering, heteroatom doping, and post-synthetic modification—and highlight their effects on activity, selectivity, and stability. Fundamental insights into the 2e⁻ ORR mechanism and evaluation metrics are also provided. Finally, we offer perspectives on current challenges and future directions, emphasizing the integration of machine learning, conductivity enhancement, and scalable synthesis to advance COFs toward practical H₂O₂ electrosynthesis. Full article

(This article belongs to the Special Issue Powering the Future: Advances of Catalysis in Batteries)

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15 pages, 1749 KiB

Open AccessArticle

Optimizing Methane Oxidative Coupling over La₂O₃: Kinetic and Product Analysis

by Zhehao Qiu and Yulu Cai

Catalysts 2025, 15(5), 499; https://doi.org/10.3390/catal15050499 - 20 May 2025

Abstract

The oxidative coupling of methane (OCM) is a promising process for converting methane directly into more valuable ethane and ethylene. In this work, high time resolution online mass spectrometry was employed to track the OCM reaction over a commercial La₂O₃ [...] Read more.

The oxidative coupling of methane (OCM) is a promising process for converting methane directly into more valuable ethane and ethylene. In this work, high time resolution online mass spectrometry was employed to track the OCM reaction over a commercial La₂O₃ catalyst, focusing on the effects of methane to oxygen ratio, gas hourly space velocity (GHSV), and the presence of H₂O and CO in the feed gas on methane conversion and C₂ yield. The results demonstrated that an optimized GHSV (44,640 to 93,000 mL·g⁻¹·h⁻¹) and methane to oxygen ratio (CH₄/O₂ = 3) would achieve the highest methane conversion and C₂ yield at 740 °C. Furthermore, at a GHSV of 44,640 mL·g⁻¹·h⁻¹, the introduction of 1% H₂O into the reaction mixture resulted in a twofold increase in C₂ yield at 650 °C, while the addition of 1% CO led to a threefold increase in C₂ yield at 550 °C. A model in which only the front-end catalyst is active was also developed to show excellent agreement with the experimental data. The relationship between catalytic performance and the effective catalyst position in the catalyst bed provides important insights into optimizing reactor design and operating conditions to maximize C₂ yield and selectivity in the OCM reaction. Full article

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14 pages, 3084 KiB

Open AccessArticle

Catalytic Hydrodeoxygenation of Pyrolysis Volatiles from Pine Nut Shell over Ni-V Bimetallic Catalysts Supported on Zeolites

by Yujian Wu, Xiwei Xu, Xudong Fan, Yan Sun, Ren Tu, Enchen Jiang, Qing Xu and Chunbao Charles Xu

Catalysts 2025, 15(5), 498; https://doi.org/10.3390/catal15050498 - 20 May 2025

Abstract

Bio-oil is a potential source for the production of alternative fuels and chemicals. In this work, Ni-V bimetallic zeolite catalysts were synthesized and evaluated in in situ catalytic hydrodeoxygenation (HDO) of pyrolysis volatiles of pine nut shell for upgraded bio-oil products. The pH [...] Read more.

Bio-oil is a potential source for the production of alternative fuels and chemicals. In this work, Ni-V bimetallic zeolite catalysts were synthesized and evaluated in in situ catalytic hydrodeoxygenation (HDO) of pyrolysis volatiles of pine nut shell for upgraded bio-oil products. The pH and lower heating value (LHV) of the upgraded bio-oil products were improved by in situ catalytic HDO, while the moisture content and density of the oil decreased. The O/C ratio of the upgraded bio-oil products decreased significantly, and the oxygenated compounds in the pyrolysis volatiles were converted efficiently via deoxygenation over Ni-V zeolite catalysts. The highest HDO activity was obtained with NiV/MesoY, where the obtained bio-oil had the lowest O/C atomic ratio (0.27), a higher LHV (27.03 MJ/kg) and the highest selectivity (19.6%) towards target arenes. Owing to the more appropriate pore size distribution and better dispersion of metal active sites, NiV/MesoY enhanced the transformation of reacting intermediates, obtaining the dominant products of phenols and arenes. A higher HDO temperature improved the catalytic activity of pyrolysis volatiles to form more deoxygenated arenes. Higher Ni loading could generate more metal active sites, thus promoting the catalyst’s HDO activity for pyrolysis volatiles. This study contributes to the development of cost-efficient and eco-friendly HDO catalysts, which are required for producing high-quality biofuel products. Full article

(This article belongs to the Topic Advanced Bioenergy and Biofuel Technologies)

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