Catalysts

24 pages, 5850 KB

Open AccessFeature PaperArticle

Effect of Promoters on Co/Al₂O₃ Catalysts for Partial Oxidation of Methane: Structure–Activity Correlations

by Khaled M. Banabdwin, Abdulaziz A. M. Abahussain, Amal BaQais, Ahmed A. Bhran, Alaaddin M. M. Saeed, Nawaf N. Alotaibi, Mohammed Abdullh Al Sudairi, Ahmed A. Ibrahim, Sunit Kumar Singh and Ahmed S Al-Fatesh

Catalysts 2025, 15(12), 1176; https://doi.org/10.3390/catal15121176 - 18 Dec 2025

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Abstract

The development of cost-effective non-noble metal catalysts for the partial oxidation of methane (POM) remains a key strategy for producing hydrogen-rich syngas while mitigating greenhouse gas emissions. In this study, cobalt-supported alumina (Co/Al₂O₃) catalysts were prepared using 5 wt.% [...] Read more.

The development of cost-effective non-noble metal catalysts for the partial oxidation of methane (POM) remains a key strategy for producing hydrogen-rich syngas while mitigating greenhouse gas emissions. In this study, cobalt-supported alumina (Co/Al₂O₃) catalysts were prepared using 5 wt.% of Co and calcined at 600, 700, and 800 °C. Subsequently, Co/Al₂O₃ catalysts were promoted with 10 wt.% Mg, Si, Ti, and Zr at the optimized calcination temperature. The catalysts were systematically characterized by FT-IR, XRD, N₂ physisorption, H₂-TPR, and XPS analyses. Catalytic activity tests for POM of CH₄ were conducted at 600 °C (CH₄/O₂ = 2 and GHSV = 14,400 mL g⁻¹ h⁻¹). Catalysts calcined at 700 °C (5Co/Al_700) exhibited the highest activity among unpromoted samples, with CH₄ conversion of 43.9% and H₂ yield of 41.8%. The superior performance was attributed to its high surface area and the abundance of reducible Co³⁺ species, generating a greater number of Co⁰ active sites. XPS results confirmed the structural stability of γ-Al₂O₃ and preserved Co–Al interactions across calcination temperatures, while promoters mainly modulated Co dispersion and redox accessibility. Among the promoted catalysts, the activity order followed: 5Co/10ZrAl > 5Co/10MgAl> unpromoted-5Co/Al_700 > 5Co/10SiAl > 5Co/10TiAl. Si and Ti promoted catalysts acquired less concentration of active sites and less activity as well. The concentration of reducible species as well as initial activity towards POM are comparable over Zr and Mg-promoted catalysts. However, earlier one has a higher edge of reducibility and sustained constant activity over time in a stream study. The Zr-promoted catalyst exhibited superior reducibility and remarkable stability, achieving 47.3% CH₄ conversion and 44.4% H₂ yield sustained over 300 min time-on-stream. TEM analysis of spent 5Co/10ZrAl indicated that Zr promotion suppressed graphitic carbon formation. Full article

(This article belongs to the Special Issue Sustainable Catalysis for Green Chemistry and Energy Transition, 2nd Edition)

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15 pages, 1628 KB

Open AccessCommunication

Magnetic Catalyzed Fenton Oxidation by CuO/ns-Fe₃O₄ for Modification of Humic Acids

by Tianbo Li, Xudong Zheng, Xinyue Hu and Guangzhou Hu

Catalysts 2025, 15(12), 1175; https://doi.org/10.3390/catal15121175 - 18 Dec 2025

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Abstract

Humic acids (HAs) are widely used as adsorbents or carriers, yet they still lack oxygenic functional groups under certain conditions. Modification via catalytic oxidation under mild conditions is an ideal method to increase the oxygenic functional groups in HAs—if simple catalyst separation could [...] Read more.

Humic acids (HAs) are widely used as adsorbents or carriers, yet they still lack oxygenic functional groups under certain conditions. Modification via catalytic oxidation under mild conditions is an ideal method to increase the oxygenic functional groups in HAs—if simple catalyst separation could be realized. Here, we report the use of CuO nanoparticles supported by Fe₃O₄ magnetic nanospheres as magnetic catalytic systems (MCSs) that could catalyze HA modification via Fenton oxidation. These MCSs can be easily magnetically separated from the products. The content of carboxyl groups increased from 2.45% to 10.47% after reaction, while the yield of modified HAs remained approximately 100%. These results indicate that oxidation with MCSs could be a potential method for HA modification. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis in China: New Horizons and Recent Advances)

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20 pages, 1881 KB

Open AccessReview

Aspergillus spp. As an Expression System for Industrial Biocatalysis and Kinetic Resolution

by Pedro Henrique Dias Garcia, Júlia Regagnin Montico, Alexssander Pontes Barichello, Cristiane Pilissão, Fabiano Jares Contesini, Uffe Hasbro Mortensen and Patrícia de Oliveira Carvalho

Catalysts 2025, 15(12), 1174; https://doi.org/10.3390/catal15121174 - 18 Dec 2025

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Abstract

This review surveys literature from 2010 to 2025 on Aspergillus-derived enzymes for kinetic resolution (KR), using conventional databases and AI-assisted platforms. Among over 340 species, A. niger, A. oryzae, and A. terreus are widely recognized as safe and industrially relevant. [...] Read more.

This review surveys literature from 2010 to 2025 on Aspergillus-derived enzymes for kinetic resolution (KR), using conventional databases and AI-assisted platforms. Among over 340 species, A. niger, A. oryzae, and A. terreus are widely recognized as safe and industrially relevant. Lipases from these fungi exhibit high stability, broad substrate specificity, and enantioselectivity, enabling efficient resolution of racemic mixtures. Advances in enzyme immobilization, protein engineering, and reaction medium optimization have enhanced catalytic performance under diverse conditions. Complementary enzymes, including esterases and epoxide hydrolases, further expand biocatalytic applications. Despite increasing demand for enantiopure compounds, challenges in yield, scalability, and enzyme discovery call for integrated molecular and process strategies. Aspergillus spp. emerge as a promising system for high-level enzyme expression, offering robust secretion capacity, efficient post-translational processing, and strong adaptability for industrial biocatalysis. Full article

(This article belongs to the Special Issue Enzyme Engineering—the Core of Biocatalysis)

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16 pages, 2470 KB

Open AccessArticle

Amorphous Nano Zero-Valent Iron (A-nZVI) Modified by Ethylenediamine for Efficient Dechlorination of Trichloroethylene: Structure, Kinetics, and Mechanism

by Zhidong Zhao, Yuqi Qiu, Baoliang Lei, Chenyang Zhang, Zhanhe Liu, Wei Wang, Haitao Wang and Tielong Li

Catalysts 2025, 15(12), 1173; https://doi.org/10.3390/catal15121173 - 18 Dec 2025

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Abstract

Amorphous nano zero-valent iron (A-nZVI) was synthesized via liquid-phase reduction and ethylenediamine (EDA) modification to enhance trichloroethylene (TCE) dechlorination. A-nZVI showed a cauliflower-like morphology, where 20–50 nm primary particles formed 500–1000 nm secondary agglomerates with a high surface area. Compared with crystalline nZVI [...] Read more.

Amorphous nano zero-valent iron (A-nZVI) was synthesized via liquid-phase reduction and ethylenediamine (EDA) modification to enhance trichloroethylene (TCE) dechlorination. A-nZVI showed a cauliflower-like morphology, where 20–50 nm primary particles formed 500–1000 nm secondary agglomerates with a high surface area. Compared with crystalline nZVI (C-nZVI), A-nZVI exhibited higher electron transfer efficiency and stronger reducing capability (potentiodynamic polarization analysis). TCE removal followed a two-stage model: a rapid adsorption–reduction phase (pseudo-second-order; q_e = 9.48 mg/g, R² = 0.998) and a slower degradation phase (pseudo-first-order; k = 0.0125 h⁻¹, R² = 0.994). No toxic intermediates (e.g., dichloroethylene or vinyl chloride) were detected; products were mainly acetylene, ethylene, and ethane. The electron utilization efficiency increased from 8.47% (C-nZVI) to 15.32% (A-nZVI), while hydrogen evolution decreased by 32%. EDA formed Fe–N coordination bonds that facilitated electron transfer and stabilized the amorphous structure. A-nZVI retained 40% of its activity after four cycles under neutral to alkaline conditions. Full article

(This article belongs to the Section Environmental Catalysis)

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15 pages, 2482 KB

Open AccessArticle

Enhancement of the Peroxidase Activity of Metal–Organic Framework with Different Clay Minerals for Detecting Aspartic Acid

by Chen Tian, Lang Zhang, Yali Yu, Ting Liu, Jianwu Chen, Jie Peng, Chu Dai and Jinhua Gan

Catalysts 2025, 15(12), 1172; https://doi.org/10.3390/catal15121172 - 17 Dec 2025

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Abstract

The strategic engineering of metal–organic frameworks (MOFs) through integration with clay minerals offers a promising route to tailor their functional properties and expand their application scope. In this study, a series of clay-MOF composites was constructed by introducing MOFs onto the surfaces of [...] Read more.

The strategic engineering of metal–organic frameworks (MOFs) through integration with clay minerals offers a promising route to tailor their functional properties and expand their application scope. In this study, a series of clay-MOF composites was constructed by introducing MOFs onto the surfaces of different clay minerals. By varying the type of clay mineral, the nature and strength of surface-active sites could be effectively modulated. Notably, the Kaolinite-based MOFs (Ka-MOF) composite exhibited superior sensitivity for the detection of aspartic acid (AA), outperforming other composite nanozymes using o-phenylenediamine (OPD) and hydrogen peroxide (H₂O₂) as substrates, with a linear detection range of 0–37.56 μM and a low detection limit of 55.7 nM. The enhanced peroxidase-like activity is attributed to the substitution of silicon in the kaolinite structure by MOF components, which increases the density of Lewis acid–base sites. These sites facilitate H₂O₂ adsorption and promote its decomposition to generate singlet oxygen (¹O₂), thereby enhancing the catalytic oxidation process. Furthermore, the probe yielded satisfactory recoveries of aspartic acid (94.2% to 98.5%) in different real water samples through spiking recovery experiments. This work not only elucidates the influence of crystal surface engineering on the optical and catalytic properties of nanozymes but also provides a robust platform for tracing amino acids and studying their environmental chemical behaviors. Full article

(This article belongs to the Special Issue Advances in MOF/COF Catalysis: Tailored Structures for Enhanced Performance)

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19 pages, 3287 KB

Open AccessArticle

Effect of Solar Irradiation on the Electrooxidation of a Dye Present in Aqueous Solution and in Real River Water

by Anabel Ramos-García, Carlos E. Barrera-Díaz, Bernardo A. Frontana-Uribe, Jorge Vazquez-Arenas and Liliana I. Ávila-Córdoba

Catalysts 2025, 15(12), 1171; https://doi.org/10.3390/catal15121171 - 16 Dec 2025

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Abstract

This study investigates the performance of an electrooxidation (EO) process employing Sb₂O₅-doped RuO₂–ZrO₂|Ti anodes integrated into a concave-cover solar still for the degradation of Allura Red dye in aqueous solution and real river water. The [...] Read more.

This study investigates the performance of an electrooxidation (EO) process employing Sb₂O₅-doped RuO₂–ZrO₂|Ti anodes integrated into a concave-cover solar still for the degradation of Allura Red dye in aqueous solution and real river water. The anode was synthesized and characterized via scanning electron microscopy (SEM) and X-ray diffraction (XRD) to confirm its porous morphology and crystalline structure. Operational parameters—including supporting electrolyte concentration, initial solution pH, and current density—were systematically optimized. Under optimal conditions (pH 2–3 and 5 mA cm⁻²), the EO process was evaluated under natural solar irradiation. Sunlight exposure increased the solution temperature from approximately 20 °C to 50 °C, enhancing molecular diffusion and mass transport, thereby accelerating decolorization kinetics. Compared to EO performed under laboratory conditions, the solar-assisted system achieved an additional 20% increase in chemical oxygen demand (COD) removal and a fast reduction in color. When applied to real Lerma River water samples under these optimal conditions, the treatment achieved approximately 50% reduction in both COD and true color, demonstrating its applicability to complex environmental matrices. These results confirm that coupling electrooxidation with solar thermal input significantly improves pollutant degradation efficiency and energy performance, establishing this integrated approach as a promising and sustainable technology for advanced wastewater treatment. Full article

(This article belongs to the Special Issue Next-Generation Catalytic Solutions for Water Purification and Wastewater Remediation)

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20 pages, 5671 KB

Open AccessArticle

Influence of Basic/Acidic Treatment on *BEA Zeolite and WO₃ Impregnation in Alcohol Dehydration Reactions

by Deborah da Silva Valadares, Roberto Chaves Fernandes, Willian Henrique Ribeiro de Carvalho, José Alves Dias and Sílvia Cláudia Loureiro Dias

Catalysts 2025, 15(12), 1170; https://doi.org/10.3390/catal15121170 - 16 Dec 2025

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Abstract

This study investigated the hierarchical structuring of *BEA zeolite using 0.2 M sodium hydroxide followed by 0.5 M hydrochloric acid (T-NaOH-HCl). Tungsten trioxide (WO₃) was then impregnated at different loadings (5, 10, 15, and 20 wt.%) onto the hierarchized materials (BEA-T). [...] Read more.

This study investigated the hierarchical structuring of *BEA zeolite using 0.2 M sodium hydroxide followed by 0.5 M hydrochloric acid (T-NaOH-HCl). Tungsten trioxide (WO₃) was then impregnated at different loadings (5, 10, 15, and 20 wt.%) onto the hierarchized materials (BEA-T). The modified zeolites were subsequently used as catalysts for the dehydration of ethanol (230 and 250 °C) and 1-propanol (230 °C). The hierarchization treatment increased the Si/Al ratio (from 13 to 39), decreased relative crystallinity by 15%, and reduced the average crystal-domain size (from 18 to 10 nm). After the NaOH–HCl treatment (BEA-T), the mesopore area increased by 7%, the mesopore volume by 19%, and the total pore volume by 12%. Conversely, the BET specific surface area and micropore volume decreased, indicating effective hierarchization of the *BEA zeolite. XRD, FT-IR and Raman confirmed the presence of monoclinic WO₃ on the BEA-T surface. MAS NMR analyses of ²⁷Al and ²⁹Si indicated that the T-NaOH-HCl treatment slightly increased the population of tetrahedral Al environments. The high conversion and selectivity from the dehydration of ethanol and 1-propanol can be attributed to a moderate reduction in the acidity of *BEA zeolite and tunned mesoporosity. Based on TON, catalysts with 10% and 20% WO₃ stood out in dehydration tests. Full article

(This article belongs to the Section Catalytic Materials)

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15 pages, 2753 KB

Open AccessArticle

Boosting Photocatalysis: Cu-MOF Functionalized with g-C₃N₄ QDs for High-Efficiency Degradation of Congo Red

by Yuhao Wang, Yuan Yang, Xinyue Zhang, Yajie Shi, Qiang Liu and Keliang Wu

Catalysts 2025, 15(12), 1169; https://doi.org/10.3390/catal15121169 - 16 Dec 2025

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Abstract

In recent years, organic dye contamination has posed a significant threat to water safety. This study presents a novel composite photocatalyst comprising graphitic carbon nitride quantum dots (g-C3N4QDs) supported on a copper-based metal–organic framework (Cu-MOF) for efficient visible-light degradation of organic pollutants. The [...] Read more.

In recent years, organic dye contamination has posed a significant threat to water safety. This study presents a novel composite photocatalyst comprising graphitic carbon nitride quantum dots (g-C3N4QDs) supported on a copper-based metal–organic framework (Cu-MOF) for efficient visible-light degradation of organic pollutants. The g-C₃N₄QDs were synthesized via a facile strategy and subsequently immobilized onto the Cu-MOF support. Comprehensive characterization including SEM, TEM, XRD, BET, UV-Vis DRS, PL, and EIS confirmed the successful formation of a heterostructure, revealing that an optimized loading of g-C₃N₄QDs significantly enhanced light absorption, facilitated charge separation, and increased the specific surface area, with the optimal composite exhibiting 273 m²/g compared to 112 m²/g for the pristine Cu-MOF. Electrochemical analyses indicated a 2.38-fold enhancement in photocurrent density and a reduced interfacial charge transfer resistance, reflecting superior electron–hole pair separation. Crucially, the optimized g-C₃N₄QDs/Cu-MOF composite demonstrated exceptional photocatalytic performance, achieving 96.6% degradation of Congo red (100 mg/L) within 30 min under visible light irradiation, substantially outperforming the 77.6% degradation attained by the pristine Cu-MOF. This enhancement is attributed to the synergistic effects of improved light harvesting, efficient interfacial charge transfer across the heterojunction, and an enlarged active surface area. The composite exhibits considerable potential as a high-performance and stable photocatalyst for purifying dye-contaminated wastewater. Full article

(This article belongs to the Section Catalytic Materials)

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24 pages, 2759 KB

Open AccessReview

Harnessing High-Valent Metals for Catalytic Oxidation: Next-Gen Strategies in Water Remediation and Circular Chemistry

by Muhammad Qasim, Sidra Manzoor, Muhammad Ikram Nabeel, Sabir Hussain, Raja Waqas, Collin G. Joseph and Jonathan Suazo-Hernández

Catalysts 2025, 15(12), 1168; https://doi.org/10.3390/catal15121168 - 15 Dec 2025

Cited by 1 | Viewed by 628

Abstract

High-valent metal species (iron, manganese, cobalt, copper, and ruthenium) based advanced oxidation processes (AOPs) have emerged as sustainable technologies for water remediation. These processes offer high selectivity, electron transfer efficiency, and compatibility with circular chemistry principles compared to conventional systems. This comprehensive review [...] Read more.

High-valent metal species (iron, manganese, cobalt, copper, and ruthenium) based advanced oxidation processes (AOPs) have emerged as sustainable technologies for water remediation. These processes offer high selectivity, electron transfer efficiency, and compatibility with circular chemistry principles compared to conventional systems. This comprehensive review discusses recent advances in the synthesis, stabilization, and catalytic applications of high-valent metals in aqueous environments. This study highlights their dual functionality, not only as conventional oxidants but also as mechanistic mediators within redox cycles that underpin next-generation AOPs. In this review, the formation mechanisms of these species in various oxidant systems are critically evaluated, highlighting the significance of ligand design, supramolecular confinement, and single-atom engineering in enhancing their stability. The integration of high-valent metal-based AOPs into photocatalysis, sonocatalysis, and electrochemical regeneration is explored through a newly proposed classification framework, highlighting their potential in the development of energy efficient hybrid systems. In addition, this work addresses the critical yet underexplored area of environmental fate, elucidating the post-oxidation transformation pathways of high-valent species, with particular attention to their implications for metal recovery and nutrient valorization. This review highlights the potential of high-valent metal-based AOPs as a promising approach for zero wastewater treatment within circular economies. Future frontiers, including bioinspired catalyst design, machine learning-guided optimization, and closed loop reactor engineering, will bridge the gap between laboratory research and real-world applications. Full article

(This article belongs to the Topic Wastewater Treatment Based on AOPs, ARPs, and AORPs)

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4 pages, 155 KB

Open AccessEditorial

Editorial for the Special Issue “Design and Application of Combined Catalysis”

by Feng Wang

Catalysts 2025, 15(12), 1167; https://doi.org/10.3390/catal15121167 - 12 Dec 2025

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Abstract

The global community is currently confronting the dual challenges of energy shortages and environmental degradation, underscoring an urgent need for green and sustainable technological solutions [...] Full article

(This article belongs to the Special Issue Design and Application of Combined Catalysis)

26 pages, 9347 KB

Open AccessFeature PaperArticle

Micron Aluminum Concurrently Encapsulated with Metallic Copper, Cobalt, and Iron Nanoparticles and Its Catalysis on Thermolysis and Combustion of Ammonium Perchlorate and Hexogen

by Xiaolan Song, Hangchen Liu, Wenhu Yan and Yi Wang

Catalysts 2025, 15(12), 1166; https://doi.org/10.3390/catal15121166 - 12 Dec 2025

Viewed by 377

Abstract

In the realm of composite solid propellant research, the enhancement of energy performance without altering the underlying formulation holds paramount significance. This investigation employed an in situ displacement technique to establish a highly reactive interface, successfully synthesizing the [nCu+nCo+nFe]/μAl composite material, which considerably [...] Read more.

In the realm of composite solid propellant research, the enhancement of energy performance without altering the underlying formulation holds paramount significance. This investigation employed an in situ displacement technique to establish a highly reactive interface, successfully synthesizing the [nCu+nCo+nFe]/μAl composite material, which considerably augmented the energy performance of RDX/AP. The decomposition pathways of ammonium perchlorate (AP) and RDX were optimized, resulting in a reduction in their thermal decomposition temperatures by 1.3 °C and 22.4 °C, respectively. Simultaneously, the highly reactive interface promoted efficient oxygen transport, thereby facilitating more rapid and complete reactions of aluminum. Moreover, the distinct dual-catalyst efficacy of the composite significantly enhanced the combustion efficiency of the composite energy micro-unit. Consequently, the [nCu+nCo+nFe]/μAl+RDX/AP composite energetic micro-units exhibited a notable decrease in combustion duration (from 1.58 s to 1.07 s) and elevated combustion flame temperatures (ranging from 1712.8 °C to 2205.6 °C) alongside an expanded combustion area, thus underscoring its potential for advanced propulsion applications. Full article

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19 pages, 6887 KB

Open AccessArticle

Influence of Ag/CeO₂-Supported Catalysts Derived from Ce-MOFs on Low-Temperature Oxidation of Unregulated Methanol Emissions from Methanol Engines

by Zhongqiang Bao, Zhenguo Li, Hao Chen, Peng Zhang, Kaifeng Wang, Ding Luo, Limin Geng and Zhanming Chen

Catalysts 2025, 15(12), 1165; https://doi.org/10.3390/catal15121165 - 12 Dec 2025

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Abstract

Methanol fuel engines can effectively reduce emissions of carbon monoxide and particulate matter, but they cause a substantial increase in emissions of unregulated pollutants like methanol and formaldehyde. In this study, Ag/CeO₂ catalysts were prepared from metal–organic framework (MOF) and silver acetate [...] Read more.

Methanol fuel engines can effectively reduce emissions of carbon monoxide and particulate matter, but they cause a substantial increase in emissions of unregulated pollutants like methanol and formaldehyde. In this study, Ag/CeO₂ catalysts were prepared from metal–organic framework (MOF) and silver acetate precursors using different methods and applied to the deep oxidation of methanol. The influence of preparation conditions on the types of active oxygen, surface chemical state, and oxygen vacancies was revealed by changing the calcination conditions and compared with the Ag/CeO₂ catalyst prepared by traditional methods. At the same time, the low-temperature reaction pathway of methanol was explored. The results showed that calcination conditions greatly affected the structure of the catalyst. Among them, Ag/CeO₂-A500 obtained by calcining Ag/Ce BTC in air at 500 °C had the best catalytic performance for methanol oxidation. The surface chemical state, overall oxygen vacancies, and the proportion of metallic silver may be key factors for its superior catalytic performance. Full article

(This article belongs to the Section Environmental Catalysis)

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13 pages, 5771 KB

Open AccessArticle

Efficient Adsorptive Desulfurization of Dibenzothiophene Using Bimetallic Ni-Cr/ZSM-5 Zeolite Catalysts

by Safa Al-deen A. Juboori and Gholamreza Moradi

Catalysts 2025, 15(12), 1164; https://doi.org/10.3390/catal15121164 - 12 Dec 2025

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Abstract

Sulfur compounds in fossil fuels pose significant environmental and industrial challenges, creating a demand for efficient and sustainable desulfurization strategies. Among the available techniques, adsorptive desulfurization has emerged as a promising approach due to its operational simplicity and low energy requirements. In this [...] Read more.

Sulfur compounds in fossil fuels pose significant environmental and industrial challenges, creating a demand for efficient and sustainable desulfurization strategies. Among the available techniques, adsorptive desulfurization has emerged as a promising approach due to its operational simplicity and low energy requirements. In this study, a Ni–Cr modified ZSM-5 zeolite was synthesized to enhance the removal of dibenzothiophene (DBT) from model fuel. The catalyst was prepared by incorporating varying metal loadings and evaluated to identify optimal performance. Structural and chemical characterizations, including FESEM, XRD, NH₃-TPD, FTIR, EDS, and BET analyses, confirmed the successful integration of nickel and chromium within the zeolite framework and demonstrated improved acidity and surface features favorable for adsorption. The catalyst containing 3% chromium and 5% nickel exhibited the highest activity, removing approximately 76% of DBT. Moreover, the optimized material maintained its adsorption efficiency over three consecutive reuse cycles, indicating strong stability and regeneration capability. Overall, the results demonstrate that Ni–Cr/ZSM-5 is a promising and sustainable adsorbent for sulfur removal applications and offers valuable potential for cleaner fuel processing technologies. Full article

(This article belongs to the Section Environmental Catalysis)

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30 pages, 6128 KB

Open AccessArticle

Sustainable Synthesis of Copper Oxide Nanoparticles: Data-Driven Photocatalysis, Pt-Free Hydrogen Production, and Antibacterial Assessment

by Umar Farooq, Mohammad Ehtisham Khan, Akbar Mohammad, Nazim Hasan, Abdullah Ali Alamri and Mukul Sharma

Catalysts 2025, 15(12), 1163; https://doi.org/10.3390/catal15121163 - 11 Dec 2025

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Abstract

This study reports the green synthesis of copper oxide nanoparticles (CuO NPs) using Oxystelma esculentum extract as a reducing and stabilizing agent. The state-of-the-art analysis confirmed their spherical morphology, with an average particle size ranging from 20 to 25 nm, while XRD indicated [...] Read more.

This study reports the green synthesis of copper oxide nanoparticles (CuO NPs) using Oxystelma esculentum extract as a reducing and stabilizing agent. The state-of-the-art analysis confirmed their spherical morphology, with an average particle size ranging from 20 to 25 nm, while XRD indicated a crystalline structure consistent with the standard JCPDS card. The photocatalytic degradation of norfloxacin (NOR) was optimized using Response Surface Methodology (RSM), which identified the optimal conditions as a reaction time = 47.51 min, CuO-NPs dose = 48.46 mg, NOR dose = 35.90 ppm, and pH = 5.23. Under these optimized conditions, the CuO NPs achieved an initial degradation efficiency of 90%. In addition to photocatalytic degradation, the hydrogen (H₂) evolution performance of the CuO NPs was evaluated, yielding a H₂ production rate of 19.52 mmol g⁻¹ h⁻¹ under visible light. Moreover, the antimicrobial activity of the CuO NPs was assessed, showing significant antibacterial effects with inhibition zones of 8 mm and 9 mm against Klebsiella and Bacillus species. The CuO NPs also exhibited potent anticancer activity with an IC₅₀ value of 15.3 ± 1.40 μM against the HeLa cell line and notable antifungal activity with inhibition rates ranging from 70% to 90% against various fungal species. Full article

(This article belongs to the Special Issue Advanced Catalysis for Energy and a Sustainable Environment)

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18 pages, 1129 KB

Open AccessFeature PaperArticle

Controlled Sequential Oxygenation of Polyunsaturated Fatty Acids with a Recombinant Unspecific Peroxygenase from Aspergillus niger

by Carlos Renato Carrillo Avilés, Marina Schramm, Sebastian Petzold, Miguel Alcalde, Martin Hofrichter and Katrin Scheibner

Catalysts 2025, 15(12), 1162; https://doi.org/10.3390/catal15121162 - 11 Dec 2025

Viewed by 435

Abstract

The metabolism of polyunsaturated fatty acids (PUFAs) is a broad research field, and the products identified so far offer potential medical and industrial applications. Epoxy fatty acids (EpFAs) act as lipid mediators that modulate renal function, angiogenesis, vascular dilatation and inflammation; moreover, they [...] Read more.

The metabolism of polyunsaturated fatty acids (PUFAs) is a broad research field, and the products identified so far offer potential medical and industrial applications. Epoxy fatty acids (EpFAs) act as lipid mediators that modulate renal function, angiogenesis, vascular dilatation and inflammation; moreover, they regulate monocyte aggregation and are involved in cardiovascular and metabolic diseases. On the other hand, EpFAs are precursors of environmentally friendly products for the plastics industry, in which the grade of epoxidation of the compounds gives the polymeric material different advantageous characteristics. The controlled chemical synthesis of poly epoxidized PUFAs is challenging as the reactions are non-selective. In contrast, the biosynthetic route based on cytochrome P450 monooxygenases and lipoxygenases is highly selective but ineffective due to the instability of the enzymes in cell-free systems. Fungal unspecific peroxygenases (UPOs, EC 1.11.2.1) with P450-like activity offer a suitable alternative for the selective synthesis of EpFAs from PUFAs. Here we demonstrate that a recombinant unspecific peroxygenase from Aspergillus niger (rAniUPO) is able to sequentially epoxidize eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to 14,15-17,18 diepoxyeicosatrienoic acid (14,15-17,18 diEpETrE) and 16,17-19,20-diepoxydocosatetraenoic acid (16,17-19,20 diEpDTE), respectively, while arachidonic acid is transformed into 13-hydroxy-14,15-epoxyeicosatrienoic acid (14,15-hepoxilin B₃). Optimal production for these oxygenated derivatives (up to 15 mg) was achieved using 2 mM hydrogen peroxide as the co-substrate. The obtained molecules were identified using high-resolution mass spectrometry and their structure was verified by NMR. Our results demonstrate the suitability of UPOs for the synthesis of EpFAs that can be used in medical research and industrial applications. Full article

(This article belongs to the Special Issue 15th Anniversary of Catalysts: The Future of Enzyme Biocatalysis)

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14 pages, 2471 KB

Open AccessFeature PaperArticle

Esterification of Free Fatty Acids Under Heterogeneous Catalysis Using Ultrasound

by Olga Semenova, Zinabu Adhena Dargie, Lena Yadgarov, Faina Nakonechny and Marina Nisnevitch

Catalysts 2025, 15(12), 1161; https://doi.org/10.3390/catal15121161 - 11 Dec 2025

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Abstract

The efficient conversion of free fatty acids (FFAs) to fatty acid methyl esters via esterification is a crucial step in biodiesel production from low-cost high-FFA feedstocks, which supports global efforts toward renewable energy and reduced dependence on fossil fuels. However, this esterification process [...] Read more.

The efficient conversion of free fatty acids (FFAs) to fatty acid methyl esters via esterification is a crucial step in biodiesel production from low-cost high-FFA feedstocks, which supports global efforts toward renewable energy and reduced dependence on fossil fuels. However, this esterification process is hindered by slow reaction kinetics, high energy demand, and low catalyst efficiencies. This study investigates tungsten disulfide (WS₂) as a heterogeneous catalyst for the esterification of a mixture of oleic and linoleic acids with methanol under ultrasonic activation, aiming to improve catalytic performance, reaction efficiency, and enhance process sustainability. Four commercial WS₂ powders from various suppliers, varying in particle size (2 μm and 90 nm), were characterized using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Micron-sized WS₂ exhibited higher catalytic activity than nano-scaled WS₂ due to a higher density of edge defects and abundance of catalytically active edge sites. Variation in reaction parameters demonstrated that the ester yield increases from 7% to 53% as the catalyst loading rises from 2% to 32% and reaches a 95% yield at an FFAs-to-methanol molar ratio of 1:15 under ultrasonic activation at 75 °C for 1 h. Comparative experiments confirmed that ultrasound treatment increases the yield of esterification compared to thermal activation. The results suggest WS₂ as a heterogeneous catalyst appropriate for efficient sonochemical esterification in biodiesel production. These kinetic and catalytic data are valuable for future process design, scalability assessments, and techno-economic evaluations of sustainable biodiesel production. Full article

(This article belongs to the Special Issue Catalysis Accelerating Energy and Environmental Sustainability)

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Open AccessArticle

Construction of Modified Silica Gel Catalysts and Their Enhancement of Fructose Dehydration for 5-HMF Production

by Liya Zheng, Yongshui Qu, Yibing Li, Yuanxin Cao, Quanyuan Wei and Ming Fang

Catalysts 2025, 15(12), 1160; https://doi.org/10.3390/catal15121160 - 10 Dec 2025

Viewed by 469

Abstract

To address the challenges of difficult recovery, significant environmental hazards associated with homogeneous catalysts, and insufficient catalytic activity of heterogeneous supports in the catalytic dehydration of fructose to produce 5-hydroxymethylfurfural (5-HMF), this study employs a straightforward nitric acid modification method to prepare an [...] Read more.

To address the challenges of difficult recovery, significant environmental hazards associated with homogeneous catalysts, and insufficient catalytic activity of heterogeneous supports in the catalytic dehydration of fructose to produce 5-hydroxymethylfurfural (5-HMF), this study employs a straightforward nitric acid modification method to prepare an acid-activated silica gel catalyst for application in this reaction system. Through systematic investigation of the influence of modification conditions on catalyst performance and economic benefits, optimal reaction conditions were determined: DMSO as the solvent, nitric acid-modified silica gel as the catalyst, a reaction temperature of 120 °C, a solid–liquid ratio of 1:30 (g∙mL⁻¹), and a fructose-to-catalyst mass ratio of 1:1. Under these conditions, the maximum 5-HMF yield reached 91.6%. Characterization via specific surface area, pore size analysis, and acid/base site characterization (NH₃-TPD) revealed that nitric acid modification preserved the silica gel’s pore structure. Through oxidative cleaning, etching to expose silanol groups, and inducing surface defects, this process significantly increased the number of acid sites on the silica gel surface, thereby enhancing catalytic activity. This study presents a low-cost, easily recoverable, and environmentally friendly heterogeneous catalytic strategy for the efficient conversion of fructose into 5-HMF. It also provides experimental guidance for the targeted functionalization of silica-based catalytic materials, holding significant implications for advancing the high-value utilization of biomass resources. Full article

(This article belongs to the Special Issue 15th Anniversary of Catalysts—Catalysis for Biomass Conversion and Valorisation)

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27 pages, 3043 KB

Open AccessReview

Recent Advances and Techno-Economic Prospects of Silicon Carbide-Based Photoelectrodes for Solar-Driven Hydrogen Generation

by Dina Bakranova, Abay Serikkanov, Farida Kapsalamova, Murat Rakhimzhanov, Zhanar Mukash and Nurlan Bakranov

Catalysts 2025, 15(12), 1159; https://doi.org/10.3390/catal15121159 - 10 Dec 2025

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Abstract

Silicon carbide (SiC) has attracted increasing attention as a robust photoelectrode material for solar water splitting due to its exceptional chemical stability, mechanical strength, and resistance to photocorrosion. Recent advances in nanostructuring—particularly the development of nanoporous SiC architectures—have dramatically improved light absorption, charge [...] Read more.

Silicon carbide (SiC) has attracted increasing attention as a robust photoelectrode material for solar water splitting due to its exceptional chemical stability, mechanical strength, and resistance to photocorrosion. Recent advances in nanostructuring—particularly the development of nanoporous SiC architectures—have dramatically improved light absorption, charge separation, and charge transport in this material. This review summarizes current strategies to enhance the PEC performance of SiC, including hierarchical nanostructuring, defect engineering (e.g., doping to tailor band structure), heterojunction formation with co-catalysts, and incorporation of plasmonic nanoparticles. Remaining challenges are discussed, notably the wide band gap of common SiC polytypes (limiting visible-light utilization) and rapid charge-carrier recombination. In addition, we examine the techno-economic prospects for SiC-based PEC systems, outlining the efficiency and durability benchmarks required for commercial hydrogen production. Finally, we propose future research directions to achieve efficient, durable SiC photoelectrodes and to guide the development of scalable PEC water-splitting devices. This review uniquely integrates material design strategies with techno-economic evaluation, providing a roadmap for SiC-based PEC systems. Full article

(This article belongs to the Section Photocatalysis)

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13 pages, 2213 KB

Open AccessArticle

Performance and Mechanism of Fe₈₀P₁₃C₇ Metal Glass in Catalytic Degradation of Methylene Blue

by Li Ma, Kun Zhang, Feilong Guo and Tiejun Kuang

Catalysts 2025, 15(12), 1158; https://doi.org/10.3390/catal15121158 - 10 Dec 2025

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Abstract

This study systematically investigates the catalytic degradation performance and reaction mechanism of Fe₈₀P₁₃C₇ Metal Glass (MG) in a Fenton-like system for the removal of Methylene Blue (MB). Kinetic experiments on degradation reveal that under acidic conditions (pH = [...] Read more.

This study systematically investigates the catalytic degradation performance and reaction mechanism of Fe₈₀P₁₃C₇ Metal Glass (MG) in a Fenton-like system for the removal of Methylene Blue (MB). Kinetic experiments on degradation reveal that under acidic conditions (pH = 3), Fe₈₀P₁₃C₇ MG exhibits exceptional catalytic activity, achieving complete degradation of a 50 mg/L MB solution within 12 min. Its degradation rate significantly surpasses that of Fe₇₈Si₉B₁₃ MG and commercially available ZVI powder. Key parameters such as catalyst dosage, H₂O₂ concentration, solution pH, and initial dye concentration were systematically examined to determine the optimal reaction conditions. The characterization results indicate that Fe₈₀P₁₃C₇ MG maintains high activity even after multiple cycles of use, attributed to surface selective corrosion and crack formation during the reaction process. This “self-renewal” mechanism continuously exposes fresh active sites. Mechanistic studies confirm that the degradation process is driven by an efficient redox cycle between Fe²⁺/Fe³⁺ within the material, ensuring sustained and stable generation of •OH, which ultimately leads to the complete mineralization of MB molecules. This research provides solid experimental and theoretical foundations for the application of Fe₈₀P₁₃C₇ MG in dye wastewater treatment. Full article

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15 pages, 3441 KB

Open AccessArticle

Performance Optimization Studies of Thermal Annealing on Pd-Co/C Cathode Electrocatalyst for Anion Exchange Membrane Fuel Cells

by Prithiv Vengatasalapathy, Ping-Hsun Chan, Fa-Cheng Su, Muhammad Javed Iqbal, Paweena Prapainainar and Hsiharng Yang

Catalysts 2025, 15(12), 1157; https://doi.org/10.3390/catal15121157 - 9 Dec 2025

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Abstract

Anion exchange membrane fuel cells (AEMFCs) are the most feasible choice of catalyst due to their high efficiency and scale of commercialization. However, the challenge posed by the sluggish kinetics of AEMFCs can only be countered by an effective electrocatalyst that enhances the [...] Read more.

Anion exchange membrane fuel cells (AEMFCs) are the most feasible choice of catalyst due to their high efficiency and scale of commercialization. However, the challenge posed by the sluggish kinetics of AEMFCs can only be countered by an effective electrocatalyst that enhances the reaction kinetics and, thereby, the fuel cell performance. The Pd-Co/C cathode catalyst is a promising choice of electrocatalyst, with the phenomenon of alloying playing a key role at appropriate temperatures and residence time distributions of annealing due to the influence of the lattice parameter, electrochemically active surface area (ECSA), and particle size. After completing the synthesis of 20 wt.% Pd-Co/C, the catalyst was treated under various annealing and loading conditions. This was subsequently followed by a series of physicochemical and electrochemical characterizations that verified the successful synthesis of the catalyst material, paving a path to optimizing the annealing temperature, annealing residence time, and catalyst loading. Further, proceeding with the fuel cell test runs with multiple profiles of the above parameters resulted in the optimization of the annealing temperature, residence time of annealing, and catalyst loading, and it was subsequently concluded that the best performance of the fuel cell was achieved when the Pd-Co/C catalyst was annealed at 500 °C for a duration of 1 h and loaded at 0.25 mg/cm², which resulted in an impeccable power density of 724 mW/cm². Full article

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15 pages, 2424 KB

Open AccessFeature PaperArticle

Ionomer-Regulated Cu/Co Tandem Catalysis for Efficient Electrochemical Nitrate-to-Ammonia Conversion

by Quan Zhou, Lewa Zhang, Ziluo Wang, Qiutong Wang and Chenyuan Zhu

Catalysts 2025, 15(12), 1156; https://doi.org/10.3390/catal15121156 - 9 Dec 2025

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Abstract

Electrochemical nitrate reduction to ammonia offers a sustainable route for nitrogen fixation, yet achieving high efficiency and selectivity remains challenging. Here, a Sustainion-enabled Cu/Co tandem catalyst is developed to couple compositional synergy with ionomer-mediated interfacial regulation. The optimized Cu₆₀Co₄₀/Sus/C [...] Read more.

Electrochemical nitrate reduction to ammonia offers a sustainable route for nitrogen fixation, yet achieving high efficiency and selectivity remains challenging. Here, a Sustainion-enabled Cu/Co tandem catalyst is developed to couple compositional synergy with ionomer-mediated interfacial regulation. The optimized Cu₆₀Co₄₀/Sus/C electrode delivers a Faradaic efficiency of 91.3% and an NH₃ yield rate of 2.63 mmol g_cat.⁻¹ h⁻¹ at −0.3 V vs. RHE, surpassing Cu-Co/Nafion/C and Cu-Co/C counterparts. Structural analyses confirm that Sustainion prevents nanoparticle aggregation and maintains robust Cu/Co interfaces. Electrochemical and in situ spectroscopic studies reveal that the cationic quaternary ammonium groups of Sustainion electrostatically enrich NO₃⁻/NO₂⁻ intermediates, facilitating their adsorption and hydrogenation toward NH₃ formation. The combined structural stabilization and intermediate modulation enable efficient tandem catalysis between Cu-driven nitrate activation and Co-mediated hydrogenation. This work provides molecular-level insight into ionomer–catalyst interactions and highlights interfacial engineering as a powerful strategy for sustainable ammonia synthesis. Full article

(This article belongs to the Special Issue Designing the Future: Covalent Organic Frameworks Meet Single-Atom Catalysts)

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40 pages, 3986 KB

Open AccessReview

Electrochemical Synthesis of TiO₂ Nanotubes for Photocatalytic Water Splitting: Mechanisms, Challenges, and Improvement Strategies

by Hamed Namdar-Asl, Farzaneh Shiran-Jang, Leila Fathyunes, M. A. Mohtadi-Bonab and Sadegh Pour-Ali

Catalysts 2025, 15(12), 1155; https://doi.org/10.3390/catal15121155 - 5 Dec 2025

Viewed by 904

Abstract

Nowadays, due to strategic reasons such as the importance of energy and environmental protection, the demand for alternatives to fossil fuels has surged. Hydrogen is considered a suitable and potential alternative energy source, promoting the development of various production technologies. However, conventional technologies [...] Read more.

Nowadays, due to strategic reasons such as the importance of energy and environmental protection, the demand for alternatives to fossil fuels has surged. Hydrogen is considered a suitable and potential alternative energy source, promoting the development of various production technologies. However, conventional technologies for hydrogen production generate a large amount of CO₂ greenhouse gases, contributing to serious environmental issues. In recent decades, TiO₂ nanotubes have emerged as effective photocatalysts for electrode reactions involving water splitting, resulting in hydrogen production. These photocatalysts utilize readily available resources: water as the raw material and sunlight as the energy source. Despite their potential, TiO₂ nanotubes face substantial challenges, including a large energy gap resulting in very low electrical conductivity, along with the recombination of electrons and electron holes during the water splitting reaction. These issues present considerable obstacles to the integration of these materials into the industrial cycle of new energy production, particularly hydrogen generation. Currently, the challenges and potential solutions associated with TiO₂ have made it one of the most extensively researched materials worldwide. In this review, the status of photocatalysts based on TiO₂ nanotubes is examined, highlighting the main challenges in this field and the proposed solutions to address these obstacles. Full article

(This article belongs to the Special Issue Advanced Semiconductor Photocatalysts)

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20 pages, 4428 KB

Open AccessArticle

Polyethylene Terephthalate Hydrolysis Catalyzed by Deep Eutectic Solvents: COSMO-RS Screening and Experimental Validation

by Nurasyqin Abdul Fattah, Muhammad Zulhaziman Mat Salleh, Nor Yuliana Yuhana, Yusuf Suleiman Dambatta and Mohamed Kamel Hadj-Kali

Catalysts 2025, 15(12), 1154; https://doi.org/10.3390/catal15121154 - 5 Dec 2025

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Abstract

Chemical recycling is one of the most prominent techniques that enables monomer recovery for plastics like polyethylene terephthalate (PET), which ultimately reduces the dependency on virgin material inputs. In this study, 40 deep eutectic solvents (DESs) were pre-screened using COSMO-RS to identify the [...] Read more.

Chemical recycling is one of the most prominent techniques that enables monomer recovery for plastics like polyethylene terephthalate (PET), which ultimately reduces the dependency on virgin material inputs. In this study, 40 deep eutectic solvents (DESs) were pre-screened using COSMO-RS to identify the best solvent for chemical recycling of PET. Quantitative evaluation was performed based on activity coefficients (γ) to assess solute–solvent interactions. Qualitatively, the sigma profile and sigma potential were analyzed to understand the polarity and affinity of each DES component. This study experimentally validated the two top-performing DESs based on COSMO-RS output. The DES formed by combining thymol with phenol (Thy/Phe (1:2)) achieved 100% PET degradation and 94.5% terephthalic acid (TPA) recovery from post-consumer PET in just 25 min. The rapid dissolution of PET into molten state accelerated the hydrolysis reaction, leading to efficient monomer recovery. The second DES, tetrabutylammonium bromide/sulfolane (TBABr/Sulf (1:7)), attained 93.7% PET degradation and 94% TPA recovery. The PET-to-solvent ratio used in this study was 0.75, while the PET-to-DES ratio in the mixture was only 0.15, the lowest reported for DES-assisted hydrolysis to date. Characterization of the recycled TPA confirmed a purity level comparable to its virgin grade, as verified by FT−IR analysis. This study presents two important outcomes. First, the use of COSMO-RS for DES selection provides a strong rationale for solvent choice in targeted reactions and processes. Second, the use of appropriate DES in this study helps reduce key parameters associated with depolymerisation process, including reaction time, temperature, and catalyst consumption. Full article

(This article belongs to the Section Catalytic Materials)

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21 pages, 3015 KB

Open AccessArticle

A Comparative Electrochemical Study of Pt and Ni–Oxide Cathodes: Performance and Economic Viability for Scale-Up Microbial Fuel Cells

by Azim Khan, Kimia Rostami, Mehdi Sedighi, Sulaiman Khan and Mostafa Ghasemi

Catalysts 2025, 15(12), 1153; https://doi.org/10.3390/catal15121153 - 5 Dec 2025

Viewed by 618

Abstract

The expensive nature and limited availability of platinum (Pt) cathodes pose a significant challenge for the widespread adoption of microbial fuel cell (MFC) technology. Although many alternatives have been studied, very few reports provide a systematic head-to-head comparison of different Ni–oxide cathodes under [...] Read more.

The expensive nature and limited availability of platinum (Pt) cathodes pose a significant challenge for the widespread adoption of microbial fuel cell (MFC) technology. Although many alternatives have been studied, very few reports provide a systematic head-to-head comparison of different Ni–oxide cathodes under the same operational conditions. This research investigates cost-effective nickel-based metal oxide composites (Ni–TiO₂, Ni–Cr₂O₃, Ni–Al₂O₃) as catalysts for the oxygen reduction reaction (ORR), using Pt as a reference point. The performance of the MFC was thoroughly evaluated in terms of power output, chemical oxygen demand (COD) removal, and Coulombic efficiency (CE). The Pt cathode exhibited the highest performance (275 mW m⁻², 87% COD removal, 35% CE), confirming its catalytic advantages. Among the alternative materials, the Ni–TiO₂ composite yielded the best outcomes (224 mW m⁻², 79% COD removal, 17.7% CE), markedly surpassing the performances of Ni–Cr₂O₃ (162 mW m⁻², 72%, 24% CE) and Ni–Al₂O₃ (134 mW m⁻², 64%, 11.6% CE). Koutecký–Levich analysis clarified the mechanisms at play: Pt facilitated a direct 4-electron ORR process, while the composites operated through a 2-electron mechanism. Notably, the semiconductor properties of Ni–TiO₂ resulted in a higher electron transfer number (n = 2.8) compared to the other composites (n ≈ 2.3), which accounts for its increased efficiency. With its low production cost, Ni–TiO₂ presents an exceptional cost-to-performance ratio. By linking catalytic performance directly to the electronic nature of the oxide supports, this study offers clear design guidelines for selecting non-precious cathodes. The dual evaluation of electrochemical efficiency and cost-to-performance distinguishes this study from prior reports and underscores its practical significance and originality. This study highlights Ni–TiO₂ as a highly sustainable and economically viable catalyst, making it a strong candidate to replace Pt for practical MFC applications that focus on simultaneous power generation and wastewater treatment. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Environmentally Compatible Reactions and Processes, 2nd Edition)

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30 pages, 2987 KB

Open AccessReview

High-Entropy Materials for Photocatalysis: A Mini Review

by Wenhao Bai, Fei Chang, Kaiwen Li, Yujjie Kou and Wei Tian

Catalysts 2025, 15(12), 1152; https://doi.org/10.3390/catal15121152 - 5 Dec 2025

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Abstract

In recent years, high-entropy materials (HEMs) have emerged as a promising multifunctional material system, garnering significant interest in the field of photocatalysis due to their tunable microstructures, diverse compositions, and unique electronic properties. Owing to their multi-element synergistic effects and abundant active sites, [...] Read more.

In recent years, high-entropy materials (HEMs) have emerged as a promising multifunctional material system, garnering significant interest in the field of photocatalysis due to their tunable microstructures, diverse compositions, and unique electronic properties. Owing to their multi-element synergistic effects and abundant active sites, high-entropy photocatalysts enable precise regulation over the separation efficiency of photo-generated charge carriers and surface reaction pathways, thereby significantly enhancing photocatalytic activity and selectivity. The high configurational entropy of these materials also imparts exceptional structural stability, allowing the catalysts to maintain long-term durability under harsh conditions, such as intense light irradiation, extreme pH levels, or redox environments. This provides a potential alternative to common issues faced by traditional photocatalysts, such as rapid deactivation and short lifespans. This review highlights recent advancements in the preparations and applications of HEMs in various photocatalytic processes, including the degradation of organic pollutants, hydrogen production, CO₂ reduction and methanation, H₂O₂ production, and N₂ fixation. The emergence of high-entropy photocatalysts has paved the way for new opportunities in environmental remediation and energy conversion. Full article

(This article belongs to the Collection Catalysis in Advanced Oxidation Processes for Pollution Control)

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13 pages, 2949 KB

Open AccessFeature PaperArticle

Boosting Furaldehyde Hydrogenation to Furfuryl Alcohol: Role of Ni in Cu₅Ni_x/SiO₂ Bimetallic Catalysts

by Yuanyuan Gao, Jieqiong Wang, Zhongyi Liu, Shuaihui Li and Qiaoyun Liu

Catalysts 2025, 15(12), 1151; https://doi.org/10.3390/catal15121151 - 5 Dec 2025

Viewed by 468

Abstract

Furfural (FAL), an important biomass-derived platform molecule, plays a vital role in bridging biorefineries and the production of high-value chemicals through its selective hydrogenation to furfuryl alcohol (FOL). In this work, a series of Cu-based bimetallic catalysts (Cu₅Ni_x/SiO₂ [...] Read more.

Furfural (FAL), an important biomass-derived platform molecule, plays a vital role in bridging biorefineries and the production of high-value chemicals through its selective hydrogenation to furfuryl alcohol (FOL). In this work, a series of Cu-based bimetallic catalysts (Cu₅Ni_x/SiO₂) were prepared by a simple impregnation method and exhibited outstanding catalytic performance for the hydrogenation of furfural under the mild conditions. When the loading of Ni was 2 wt%, the optimal catalytic activity was obtained at 150 °C and 1 MPa H₂, achieving a furfural conversion of 97.3%. This catalyst also showed excellent stability, maintaining high activity and selectivity toward FOL after five consecutive reaction cycles. Structural characterizations using X-ray diffraction (XRD), Hydrogen temperature-programmed reduction (H₂-TPR), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) revealed strong electronic interactions between Cu and Ni species. The introduction of Ni promoted the reduction of Ni²⁺ and improved the dispersion of Cu, which in turn increased the number of accessible active sites and facilitated the hydrogenation process. This synergistic effect between Cu and Ni provides an efficient and low-cost strategy for the selective hydrogenation of biomass-derived furfural to high-valued chemicals. Full article

(This article belongs to the Special Issue Back to the Future: Advances in Porous and Nanoscale Catalysts for Biomass Conversion to Value-Added Products)

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14 pages, 3551 KB

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Enhancement of Cellulase Production by Penicillium oxalicum Using Traditional Chinese Medicine Residue and Its Application in Flavonoid Extraction

by Xiaoxi Zeng, Xuan Li, Wenjun Guan, Zilin Hu, Yuanke Zhang, Cheng Zhang, Song Ran and Liang Ma

Catalysts 2025, 15(12), 1150; https://doi.org/10.3390/catal15121150 - 5 Dec 2025

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Abstract

Cellulase is an inducible enzyme. By using traditional Chinese medicine residues (TCMRs) as inducer for microbial cellulase, the enzyme’s production yield can be improved. Additionally, this approach enables the resource utilization and harmless treatment of TCMRs. In this study, a fungus that can [...] Read more.

Cellulase is an inducible enzyme. By using traditional Chinese medicine residues (TCMRs) as inducer for microbial cellulase, the enzyme’s production yield can be improved. Additionally, this approach enables the resource utilization and harmless treatment of TCMRs. In this study, a fungus that can use TCMRs as a substrate was screened and identified as Penicillium oxalicum. The fungus grew well in the culture medium containing TCMRs, and the highest filter paper activity (FPA) reached 2.06 IU/mL in forsythia leaves residue (FR). After fermentation, the FR exhibited the highest weight loss rate, reaching 22.67%. Enzyme production conditions were optimized using the Plackett–Burman (PB) and Central –Composite Design (CCD) methods. The FPA could reach 2.75 IU/mL under the optimal conditions of FR concentration of 24.84 g/L, (NH₄)₂SO₄ concentration of 2 g/L, temperature of 34.44 °C, pH 6.20, rotational speed of 200 rpm, and inoculum size of 6%, which was 33.50% higher than that before optimization. The crude cellulase was used to extract total flavonoids from TCMRs, and the extraction rate of total flavonoids increased by 24.2–55.1%. The results demonstrated that TCMRs are effective for inducing substrates for cellulase production by Penicillium oxalicum Ti-11. Furthermore, the crude cellulase produced significantly promoted total flavonoids extraction from TCMRs. Full article

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17 pages, 4281 KB

Open AccessFeature PaperArticle

Development of Highly Active and Stable SmMnO₃ Perovskite Catalysts for Catalytic Combustion

by Dinghua Ruan, Shipeng Wu, Chenyi Yuan, Zhen Huang, Wei Shen and Hualong Xu

Catalysts 2025, 15(12), 1149; https://doi.org/10.3390/catal15121149 - 5 Dec 2025

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Abstract

The development of highly efficient and stable non-noble metal catalysts for volatile organic compound (VOCs) abatement remains a pressing challenge. Mn-based perovskites exhibit superior thermal stability as redox catalysts but suffer from limited activity in light alkane combustion. This study systematically investigates the [...] Read more.

The development of highly efficient and stable non-noble metal catalysts for volatile organic compound (VOCs) abatement remains a pressing challenge. Mn-based perovskites exhibit superior thermal stability as redox catalysts but suffer from limited activity in light alkane combustion. This study systematically investigates the performance of SmMnO₃ (SMO) perovskite catalysts for propane oxidation through selective etching of Sm species. By precisely controlling the etching process, the removal of surface Sm exposes more active sites and significantly increases the specific surface area from 22.05 m²·g⁻¹ for pristine SMO to 66.15 m²·g⁻¹. SEM and N₂ adsorption–desorption analysis revealed that prolonged etching induces surface roughening and pore channel expansion. XPS and XANES measurements confirmed that an increased Mn⁴⁺/Mn³⁺ ratio enhances reactant adsorption and accessibility to active sites. The etched catalysts exhibited markedly improved activity for propane oxidation, achieving a ~50 °C reduction in light-off temperature compared to the raw SMO. This performance enhancement is attributed to the synergistic effects of enhanced oxygen mobility, elevated Mn⁴⁺ content, and abundant oxygen vacancies. Further characterization via Raman spectroscopy and H₂-TPR revealed weakened Jahn–Teller distortion and lower reduction temperatures, reflecting optimized Mn–O interactions and superior redox properties. Among the samples, SMO-20 demonstrated exceptional stability. Moreover, the SMO-20/cordierite monolithic catalyst maintained outstanding catalytic performance over 1000 h of operation. This work offers a facile and effective approach to engineer perovskite catalysts and provides new insights into structure–activity relationships in VOC oxidation. Full article

(This article belongs to the Special Issue Advanced Catalysts for Energy Conversion and Environmental Protection)

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12 pages, 1547 KB

Open AccessArticle

Rational Designing and Stepwise Cascade for Efficient Biosynthesis of Raspberry Ketone

by Yang Yang, Kangkang Shang, Xiaorui Gao, Xingmiao Zhu, Mengying Ling, Pu Zheng, Shichao Xu and Pengcheng Chen

Catalysts 2025, 15(12), 1148; https://doi.org/10.3390/catal15121148 - 5 Dec 2025

Viewed by 495

Abstract

Raspberry ketone (RK) is the primary aromatic compound in raspberry fruit, which is widely utilized in perfume, cosmetics, and food additive industries. Currently, RK is predominantly produced chemically. RK biosynthesis through enzyme or whole cell has garnered significant attention due to the mild [...] Read more.

Raspberry ketone (RK) is the primary aromatic compound in raspberry fruit, which is widely utilized in perfume, cosmetics, and food additive industries. Currently, RK is predominantly produced chemically. RK biosynthesis through enzyme or whole cell has garnered significant attention due to the mild reaction conditions and the process being regarded as ‘natural’. This study proposed a ‘dual-microorganism, two-phase’ stepwise cascade strategy to produce RK from an economical precursor, 4-hydroxybenzaldehyde (4-HBD). An acetone-tolerant deoxyribose-phosphate aldolase DERA_Ec (S238D) mutant was obtained through a site-specific rigidification strategy for converting 4-HBD to 4-hydroxybenzylaceton (4-HBA). Then, an engineered E. coli co-expressing isocitrate dehydrogenase and raspberry ketone synthase RiRZS1 with a citrate-sodium citrate buffer to recycle nicotinamide adenine dinucleotide phosphate (NADPH) was constructed for the conversion of 4-HBA to RK. The final concentration of RK was 50.00 ± 1.92 mmol·L⁻¹ with a yield of 86.96%. This strategy provides a scalable coenzyme self-recycling and two-phase catalysis platform for high-value phenolic compounds. Full article

(This article belongs to the Section Biocatalysis)

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18 pages, 3492 KB

Open AccessFeature PaperArticle

Construction of a Visible Light-Driven LaFeO₃/Bi₄Ti₃O₁₂ Heterojunction Photocatalyst Towards Removal of Tetracycline in Aquatic Environment

by Weifang Chen, Na Zhao, Shuo Zhang and Qiaoqiao Ma

Catalysts 2025, 15(12), 1147; https://doi.org/10.3390/catal15121147 - 5 Dec 2025

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Abstract

A LaFeO₃/Bi₄Ti₃O₁₂ heterojunction photocatalyst composite was constructed for the removal of tetracycline (TC). The structure, morphology, and elemental composition of the composite were systematically characterized using tools such as XRD, SEM, and XPS. The results from [...] Read more.

A LaFeO₃/Bi₄Ti₃O₁₂ heterojunction photocatalyst composite was constructed for the removal of tetracycline (TC). The structure, morphology, and elemental composition of the composite were systematically characterized using tools such as XRD, SEM, and XPS. The results from characterization jointly verified the successful construction of a LaFeO₃/Bi₄Ti₃O₁₂ heterojunction. UV–vis DRS analysis further revealed a narrowing of the optical bandgap from 3.29 eV to 2.24 eV, which enhanced visible-light absorption. Characterization via XPS identified the presence of Fe²⁺/Fe³⁺ mixed valence states, while bismuth predominantly existed in the stable Bi³⁺ state. Under simulated sunlight (300 W xenon lamp) irradiation, the photocatalytic performance of LaFeO₃/Bi₄Ti₃O₁₂ was systematically evaluated. The results demonstrated that the LaFeO₃/Bi₄Ti₃O₁₂ composite achieved a removal efficiency of 95% for TC within 120 min, with a reaction rate constant of 0.023 min⁻¹. The construction of heterojunction greatly increased not only the removal efficiency but also the reaction rate. For instance, the first-order reaction rate constants of LaFeO₃/Bi₄Ti₃O₁₂ were 3.8 and 4.7 times higher than those of pure LaFeO₃ and Bi₄Ti₃O₁₂. TC removal by the composite was affected by dosage, initial TC concentration, and pH of the water. The composite exhibited the best performance at a dosage of 1.6 g/L with a pH around 7–8 and an initial TC concentration less than 20 mg/L. Anions such as Cl⁻ and NO₃⁻ had minimal impact on its photocatalytic activity, whereas H₂PO₄⁻, humic acid, showed inhibitory effects. Free radical trapping experiments further confirmed that holes (h⁺) and hydroxyl radicals (·OH) were the primary active species in the process. Full article

(This article belongs to the Special Issue Recent Advances in Photocatalytic Treatment of Pollutants in Water, 2nd Edition)

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