Catalysts

20 pages, 4861 KiB

Open AccessEditor’s ChoiceArticle

Improving the Catalytic Selectivity of Reverse Water–Gas Shift Reaction Catalyzed by Ru/CeO₂ Through the Addition of Yttrium Oxide

by Alfredo Solís-García, Karina Portillo-Cortez, David Domínguez, Sergio Fuentes-Moyado, Jorge N. Díaz de León, Trino A. Zepeda and Uriel Caudillo-Flores

Catalysts 2025, 15(4), 301; https://doi.org/10.3390/catal15040301 - 23 Mar 2025

Cited by 1 | Viewed by 916

Abstract

This study reports the synthesis, characterization, and catalytic performance of a series of catalysts of Ru supported on CeO₂-Y₂O₃ composites (Ru/CeYX; X = 0, 33, 66, and 100 wt.% Y₂O₃) for CO₂ hydrogenation. [...] Read more.

This study reports the synthesis, characterization, and catalytic performance of a series of catalysts of Ru supported on CeO₂-Y₂O₃ composites (Ru/CeYX; X = 0, 33, 66, and 100 wt.% Y₂O₃) for CO₂ hydrogenation. Supported material modification (Y₂O₃-CeO₂), by the Y₂O₃ incorporation, allowed a change in selectivity from methane to RWGS of the CO₂ hydrogenation reaction. This change in selectivity is correlated with the variation in the physicochemical properties caused by Y₂O₃ addition. X-ray diffraction (XRD) analysis confirmed the formation of crystalline fluorite-phase CeO₂ and α-Y₂O₃. High-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDS) elemental mapping revealed the formation of a homogeneous CeO₂-Y₂O₃ nanocomposite. As the Y₂O₃ content increased, the specific surface area, measured by BET, showed a decreasing trend from 106.3 to 51.7 m² g⁻¹. X-ray photoelectron spectroscopy (XPS) of Ce3d indicated a similar Ce³⁺/Ce⁴⁺ ratio across all CeO₂-containing materials, while the O1s spectra showed a reduction in oxygen vacancies with increasing Y₂O₃ content, which is attributed to the decreased surface area upon composite formation. Catalytically, the addition of Y₂O₃ influenced both conversion and selectivity. CO₂ conversion decreased with increasing Y₂O₃ content, with the lowest conversion observed for Ru/CeY100. Regarding selectivity, methane was the dominant product for Ru/CeY0 (pure CeO₂), while CO was the main product for Ru/CeY33, Ru/CeY66, and Ru/CeY100, indicating a shift towards the reverse water–gas shift (RWGS) reaction. The highest RWGS reaction rate was observed with the Ru/CeY33 catalyst under all tested conditions. The observed differences in conversion and selectivity are attributed to a reduction in active sites due to the decrease in surface area and oxygen vacancies, both of which are important for CO₂ adsorption. In order to verify the surface species catalytically active for RWGS, the samples were characterized by FTIR spectroscopy under reaction conditions. Full article

(This article belongs to the Special Issue Design and Synthesis of Nanostructured Catalysts, 2nd Edition)

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22 pages, 8771 KiB

Open AccessEditor’s ChoiceArticle

Controlled Synthesis of Nickel Phosphides in Hollow N, P Co-Doped Carbon: In Situ Transition to (Oxy)hydroxide Phases During Oxygen Evolution Reaction

by David Ríos-Ruiz, Pablo Arévalo-Cid, Jesús Cebollada, Verónica Celorrio, Miran Čeh, Sandra Drev and María Victoria Martínez-Huerta

Catalysts 2025, 15(3), 292; https://doi.org/10.3390/catal15030292 - 20 Mar 2025

Viewed by 985

Abstract

Developing sustainable and efficient electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing energy storage technologies. This study explored the dual role of phosphorus as a dopant in carbon matrices and a key component in nickel phosphides (Ni₂P and [...] Read more.

Developing sustainable and efficient electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing energy storage technologies. This study explored the dual role of phosphorus as a dopant in carbon matrices and a key component in nickel phosphides (Ni₂P and Ni₁₂P₅), synthesized using dopamine (PDA) and ammonium phosphate as eco-friendly precursors. The phase formation of nickel phosphides was found to be highly dependent on the P/PDA ratio (0.15, 0.3, 0.6, and 0.9), allowing for the selective synthesis of Ni₂P or Ni₁₂P₅. Operando Raman spectroscopy revealed that both phases undergo surface transformation into nickel (oxy)hydroxide species under OER conditions, yet Ni₂P-based catalysts demonstrated superior activity and long-term stability. This enhancement is attributed to efficient electron transfer at the dynamic Ni₂P/NiOOH interface. Additionally, hollow nanostructures formed at intermediate P/PDA ratios (≤0.3) via the Kirkendall effect and Ostwald ripening contributed to an increased specific surface area and micropore volume, further improving the catalytic performance. Electrochemical impedance spectroscopy confirmed reduced interfacial resistance and enhanced charge transport. These findings offer new insights into the rational design of high-performance electrocatalysts and propose a green, tunable synthesis approach for advanced energy conversion applications. Full article

(This article belongs to the Special Issue Recent Advances in Electrocatalysis and Future Perspective)

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23 pages, 5288 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Review on Green Hydrogen Production by Aqueous Phase Reforming of Lignocellulose and Derivatives

by Mengjie Li, Weilong Ji, Chunjie Huang, Xiaoqin Si, Qian Liu, Rui Lu and Tianliang Lu

Catalysts 2025, 15(3), 280; https://doi.org/10.3390/catal15030280 - 17 Mar 2025

Cited by 1 | Viewed by 1032

Abstract

With the intensification of the global energy crisis, hydrogen has attracted significant attention as a high-energy-density and zero-emission clean energy source. Traditional hydrogen production methods are dependent on fossil fuels and simultaneously contribute to environmental pollution. The aqueous phase reforming (APR) of renewable [...] Read more.

With the intensification of the global energy crisis, hydrogen has attracted significant attention as a high-energy-density and zero-emission clean energy source. Traditional hydrogen production methods are dependent on fossil fuels and simultaneously contribute to environmental pollution. The aqueous phase reforming (APR) of renewable biomass and its derivatives has emerged as a research hotspot in recent years due to its ability to produce green hydrogen in an environmentally friendly manner. This review provides an overview of the advancements in APR of lignocellulosic biomass as a sustainable and environmentally friendly method for hydrogen production. It focuses on the reaction pathways of various biomass feedstocks (such as glucose, cellulose, and lignin), as well as the types and performance of catalysts used in the APR process. Finally, the current challenges and future prospects in this field are briefly discussed. Full article

(This article belongs to the Special Issue Plant-Derived Biomass Catalytic and Biocatalytic Transformation into Biorefinery Products)

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22 pages, 3017 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Advances in the Enzymatic Synthesis of Nucleoside-5′-Triphosphates and Their Analogs

by Maryke Fehlau, Sarah Westarp, Peter Neubauer and Anke Kurreck

Catalysts 2025, 15(3), 270; https://doi.org/10.3390/catal15030270 - 13 Mar 2025

Cited by 2 | Viewed by 2072

Abstract

Nucleoside-5′-triphosphates (5′-NTPs) are essential building blocks of nucleic acids in nature and play an important role in molecular biology, diagnostics, and mRNA therapeutic synthesis. Chemical synthesis has long been the standard method for producing modified 5′-NTPs. However, chemical routes face limitations, including low [...] Read more.

Nucleoside-5′-triphosphates (5′-NTPs) are essential building blocks of nucleic acids in nature and play an important role in molecular biology, diagnostics, and mRNA therapeutic synthesis. Chemical synthesis has long been the standard method for producing modified 5′-NTPs. However, chemical routes face limitations, including low regio- and stereoselectivity, along with the need for protection/deprotection cycles, resulting in low yields, high costs, and lengthy processes. In contrast, enzymatic synthesis methods offer significant advantages, such as improved regio- and stereoselectivity and the use of mild reaction conditions, which often leads to higher product yields in “one-pot” reactions. Despite the extensive review of chemical synthesis routes for 5′-NTPs, there has not yet been any comprehensive analysis of enzymatic approaches. Initially, this review provides a brief overview of the enzymes involved in nucleotide metabolism, introducing valuable biocatalysts for 5’-NTP synthesis. Furthermore, the available enzymatic methods for efficient 5′-NTP synthesis using purified enzymes and starting from either nucleobases or nucleosides are examined, highlighting their respective advantages and disadvantages. Special attention is also given to the importance of ATP regeneration systems for 5′-NTP synthesis. We aim to demonstrate the remarkable potential of enzymatic in vitro cascade reactions, promoting their broader application in both basic research and industry. Full article

(This article belongs to the Special Issue Feature Papers in Catalysis for Pharmaceuticals)

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25 pages, 1912 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Review of Materials for Carbon Dioxide Capture

by Ashish Rana and Jean M. Andino

Catalysts 2025, 15(3), 273; https://doi.org/10.3390/catal15030273 - 13 Mar 2025

Cited by 3 | Viewed by 2341

Abstract

The increasing concentration of carbon dioxide (CO₂) in the atmosphere is a significant contributor to global warming and climate change. Effective CO₂ capture and storage technologies are critical to mitigating these impacts. This review explores various materials used for CO [...] Read more.

The increasing concentration of carbon dioxide (CO₂) in the atmosphere is a significant contributor to global warming and climate change. Effective CO₂ capture and storage technologies are critical to mitigating these impacts. This review explores various materials used for CO₂ capture, focusing on the latest advancements and their applications. The review categorizes these materials into chemical and physical absorbents, highlighting their unique properties, advantages, and limitations. Chemical absorbents, such as amine-based solutions and hydroxides, have been widely used due to their high CO₂ absorption capacities and established technological frameworks. However, they often suffer from high energy requirements for regeneration and potential degradation over time. Recent developments in ionic liquids (ILs) and polymeric ionic liquids (PILs) offer promising alternatives, providing tunable properties and lower regeneration energy. Physical absorbents, including advanced solvents like nanofluids and ionic liquids as well as industrial processes like selexol, rectisol, and purisol, demonstrate enhanced CO₂ capture efficiency under various conditions. Additionally, adsorbents like activated carbon, zeolites, metal-organic frameworks (MOFs), carbon nanotubes (CNTs), and layered double hydroxides (LDHs) play a crucial role by providing high surface areas and selective CO₂ capture through physical or chemical interactions. This paper summarizes the state of research on different materials and discusses their advantages and limitations while being used in CO₂ capture technologies. This review also discussed multiple studies examining the use of catalysts and absorption mechanisms in combination with different sorbents, focusing on how these approaches enhance the efficiency of absorption and desorption processes. Through a comprehensive analysis, this review aims to provide valuable insights into the type of materials that are most suitable for CO₂ capture and also provides directions for future research in this area. Full article

(This article belongs to the Special Issue Feature Review Papers in Catalysis for Sustainable Energy)

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17 pages, 28408 KiB

Open AccessEditor’s ChoiceArticle

Immobilization of Enzymes on Electrodes and Electrode Design in Biofuel Cells

by Chang Yen Chen, Adama A. Bojang, Damayanti Damayanti and Ho Shing Wu

Catalysts 2025, 15(3), 253; https://doi.org/10.3390/catal15030253 - 6 Mar 2025

Viewed by 1134

Abstract

In an enzyme-based fuel cell system, glucose oxidase and laccase were immobilized on carbon paper as the anode and cathode electrodes. A conductive polymer (polypyrrole) was added to improve conductivity. The mediator and enzymes were mixed in a phosphate-buffer solution for entrapment. A [...] Read more.

In an enzyme-based fuel cell system, glucose oxidase and laccase were immobilized on carbon paper as the anode and cathode electrodes. A conductive polymer (polypyrrole) was added to improve conductivity. The mediator and enzymes were mixed in a phosphate-buffer solution for entrapment. A Nafion 212 membrane separated the two half-cells. Power density measurements were taken at a glucose concentration of 10 mM across different operating voltages. Potassium hexacyanoferrate III was used as a redox mediator in the anode and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) in the cathode to boost power output. The biofuel cells, constructed from acrylic (40 × 50 × 50 mm) with a working volume of 20 × 30 × 40 mm, were assembled using a rubber gasket to secure the Nafion membrane. The use of micropore tape covering the electrodes extended the system’s operational lifespan. Without the micropore tape, the maximum power density was 57.6 μW/cm² at 0.24 V. With the micropore tape, the cell achieved a maximum power density of 324.9 μW/cm² at 0.57 V, sustaining performance for 20 days. Thus, micropore tape effectively enhances enzyme retention and biofuel cell performance. Full article

(This article belongs to the Special Issue Enzyme and Biocatalysis Application)

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14 pages, 6301 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Photocatalytic Cement Mortar with Durable Self-Cleaning Performance

by Zhuoying Jiang, Bin Zhang and Xiong Yu

Catalysts 2025, 15(3), 249; https://doi.org/10.3390/catal15030249 - 6 Mar 2025

Viewed by 955

Abstract

Nano-TiO₂-modified mortars are fabricated by introducing TiO₂ nanoparticles to the conventional mortar mix with designed mixing and curing procedures. It was found that additional TiO₂ nanoparticles can accelerate hydration and improve the air void distribution in the mortar matrix. [...] Read more.

Nano-TiO₂-modified mortars are fabricated by introducing TiO₂ nanoparticles to the conventional mortar mix with designed mixing and curing procedures. It was found that additional TiO₂ nanoparticles can accelerate hydration and improve the air void distribution in the mortar matrix. The experiments also showed that 0.5 wt.% and 1 wt.% TiO₂-modified mortar has a comparable mechanical strength to traditional cement mortar. The abrasion resistance is improved with nanoparticles at 0.5 wt.% TiO₂ concentration. The photocatalytic performance of photocatalytic mortar was confirmed by a methylene blue decomposition test. Finally, a multi-physics computational model was constructed to assess the effects of photocatalytic mortar coated on building in air quality improvements in the neighboring area. The benefits are affected by different nano-TiO₂ concentrations, as well as wind conditions in the neighborhood. Overall, this study shows that properly designed nano-TiO₂-modified mortar is promising to achieve multifunctional performance in terms of mechanical strength and durability as well as autogenous self-cleaning of surrounding environment. Full article

(This article belongs to the Special Issue TiO₂ Photocatalysts: Design, Optimization and Application)

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36 pages, 2131 KiB

Open AccessEditor’s ChoiceReview

Catalytic Properties and Structural Optimization of Solid Transesterification Catalysts to Enhance the Efficiency of Biodiesel Synthesis

by Xiangyang Li, Siwei Zhang, Xunxiang Jia, Weiji Li and Jiliang Song

Catalysts 2025, 15(3), 239; https://doi.org/10.3390/catal15030239 - 1 Mar 2025

Viewed by 2108

Abstract

The transition to sustainable energy has given biodiesel prominence as a renewable alternative to diesel. This review highlights the development and optimization of solid transesterification catalysts, contributing greatly to the efficiency of biodiesel synthesis. These heterogeneous catalysts are constituted of titanium-, zinc-, and [...] Read more.

The transition to sustainable energy has given biodiesel prominence as a renewable alternative to diesel. This review highlights the development and optimization of solid transesterification catalysts, contributing greatly to the efficiency of biodiesel synthesis. These heterogeneous catalysts are constituted of titanium-, zinc-, and bio-based systems and significant advantages such as reusability, thermal stability, and the ability to be synthesized from low-grade feedstocks. Recent advancements in structural optimization, with nano-structured titanium dioxide having the potential of yielding higher biodiesel production up to a yield of 96–98% within 5–7 cycles, render improved stability and catalytic performance. Several characterization techniques, such as the Brunauer–Emmett–Teller method, X-ray diffraction, and temperature-programmed desorption, are instrumental in the characterization of these catalysts and their effective design. However, despite their substantial promise, there are still problems to be dealt with in the large-scale production, regeneration, and service life stability of these catalysts. This account collates recent innovations, analytical mechanisms, and prospective directions which elucidate the potential of solid transesterification catalysts in furthering biodiesel technology and the sustainable production of chemicals. Full article

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14 pages, 2324 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Engineering Synergistic 2D/1D ReS₂-LaFeO₃ Nanohybrids for Enhanced Visible-Light-Driven Photocatalytic Performance

by Obed Graham Keelson, Rajeev Kumar, Amit Kumar Shringi, Hazel Achieng Ouma, Pooja D. Walimbe and Fei Yan

Catalysts 2025, 15(3), 224; https://doi.org/10.3390/catal15030224 - 27 Feb 2025

Cited by 1 | Viewed by 756

Abstract

This study investigates the synergistic properties of 2D/1D ReS₂-decorated LaFeO₃ nanohybrids, presenting a unique approach to photocatalytic dye degradation. Through facile hydrothermal synthesis, we fabricated these nanohybrids with varying ReS₂ loadings. Notably, the 5 wt% ReS₂-LaFeO₃ [...] Read more.

This study investigates the synergistic properties of 2D/1D ReS₂-decorated LaFeO₃ nanohybrids, presenting a unique approach to photocatalytic dye degradation. Through facile hydrothermal synthesis, we fabricated these nanohybrids with varying ReS₂ loadings. Notably, the 5 wt% ReS₂-LaFeO₃ nanohybrid exhibited highly efficient visible-light-driven photocatalytic degradation of Congo red (CR) dye, achieving 82% degradation within 180 min. This enhanced performance can be attributed to synergistic effects arising from the unique 2D/1D architecture and the modified charge-transfer properties within the 2D/1D ReS₂-LaFeO₃ heterostructure. These findings demonstrate the potential of these multifunctional nanohybrids for applications in environmental remediation. Full article

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27 pages, 4982 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Design and Synthesis of Self-Supported Water-Splitting Transition Metal-Based Electrocatalysts via Electrospinning

by Sai Che, Yu Jia and Yongfeng Li

Catalysts 2025, 15(3), 205; https://doi.org/10.3390/catal15030205 - 21 Feb 2025

Viewed by 1472

Abstract

Recent advances in transition metal-based electrocatalysts have significantly enhanced the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water electrocatalysis. Self-supported electrodes, where active sites are directly integrated with substrates, offer superior kinetics and stability compared to traditional powder-based electrocatalysts. The [...] Read more.

Recent advances in transition metal-based electrocatalysts have significantly enhanced the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water electrocatalysis. Self-supported electrodes, where active sites are directly integrated with substrates, offer superior kinetics and stability compared to traditional powder-based electrocatalysts. The electrospinning technique is particularly effective for fabricating self-supported electrocatalysts with high surface areas, porosity, and uniform distribution of active sites, leading to improved catalytic performance. Despite extensive research on self-supported electrocatalysts, a comprehensive review focusing on those developed via electrospinning remains scarce. This review provides a detailed overview of the electrospinning process, the fundamental principles of water electrocatalysis, and recent progress in the development of transition metal-based electrocatalysts fabricated through this approach. Full article

(This article belongs to the Special Issue Feature Review Papers in Electrocatalysis)

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10 pages, 2235 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Enhancing C-C Coupling in CO₂ Electroreduction by Engineering Pore Size of Porous Carbon-Supported Cu Catalysts

by Aiming Huang, Jiayue Yu, Junjun Zhang, Yifan Zhang, Yang Wu, Yong Wang and Wen Luo

Catalysts 2025, 15(3), 199; https://doi.org/10.3390/catal15030199 - 20 Feb 2025

Cited by 11 | Viewed by 1085

Abstract

The electroreduction of CO₂ (CO₂RR) is a promising and environmentally sustainable approach to closing the carbon cycle. However, achieving high activity and selectivity for multicarbon (C₂₊) products remains a significant challenge due to the complexity of reaction pathways. [...] Read more.

The electroreduction of CO₂ (CO₂RR) is a promising and environmentally sustainable approach to closing the carbon cycle. However, achieving high activity and selectivity for multicarbon (C₂₊) products remains a significant challenge due to the complexity of reaction pathways. In this study, porous carbon-supported copper catalysts (CuHCS) with pore sizes of 120 nm (CuHCS120) and 500 nm (CuHCS500) were synthesized to tailor the microenvironment at the electrode–electrolyte interface and enhance product selectivity. CuHCS120 achieved a maximum faradaic efficiency (FE) for C₂₊ products of 46%, double that of CuHCS500 (23%). In contrast, CuHCS500 showed a higher FE for CO (36%) compared to CuHCS120 (14%) at the same potential. In-depth ex situ and in situ investigations revealed that smaller pores promote the enrichment and adsorption of *CO intermediates, thereby enhancing C–C coupling and the formation of C₂₊ products. These findings underscore the critical role of structural confinement in modulating the catalytic microenvironment and provide valuable insights for the rational design of advanced catalysts for CO₂RR. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis and Electrocatalysis)

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20 pages, 3151 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Environmental Impacts on the Photocatalytic Activities of Anatase and Rutile

by Karolina Solymos, Áron Ágoston, Tamás Gyulavári, Lilla Szalma, Milica Todea, Ákos Kukovecz, Zoltán Kónya and Zsolt Pap

Catalysts 2025, 15(2), 190; https://doi.org/10.3390/catal15020190 - 18 Feb 2025

Cited by 1 | Viewed by 960

Abstract

Titanium dioxide (TiO₂) nanoparticles (NPs) are widely used in various industries and are increasingly found in environmental systems, especially in soil. However, the environmental behavior of TiO₂ NPs is still poorly understood. Hence, this study aims to fill this gap [...] Read more.

Titanium dioxide (TiO₂) nanoparticles (NPs) are widely used in various industries and are increasingly found in environmental systems, especially in soil. However, the environmental behavior of TiO₂ NPs is still poorly understood. Hence, this study aims to fill this gap by investigating the short- and long-term effects of soil solutions on anatase and rutile NPs. The experiments were carried out using two soil types, which have very different chemical properties, in order to obtain a more nuanced picture of how these factors affect the stability, surface chemistry, and photocatalytic activity of TiO₂ NPs. The results indicate that acidic soil solutions with lower ionic strength tend to enhance the stability of TiO₂ NPs by preventing aggregation, while alkaline solutions with higher ionic strength promote aggregation and reduce photocatalytic activity by blocking active sites. Additionally, the adsorption of organic matter and other soil components on the nanoparticle surface further complicates their behavior, potentially reducing their photocatalytic efficiency. The interaction time plays a crucial role in determining the long-term fate of TiO₂ NPs in soil environments. Extended exposure to soil solutions leads to changes in crystallite size, surface charge, and the adsorption of functional groups, which, in turn, affect the NPs’ photocatalytic properties. Full article

(This article belongs to the Special Issue Photocatalysis: Past, Present, and Future Outlook)

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20 pages, 4626 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Enzymatic Oxidation of Hydroxytyrosol in Deep Eutectic Solvents for Chitosan Functionalization and Preparation of Bioactive Nanogels

by Myrto G. Bellou, Anastasia Skonta, Alexandra V. Chatzikonstantinou, Angeliki C. Polydera, Petros Katapodis, Epaminondas Voutsas and Haralambos Stamatis

Catalysts 2025, 15(2), 180; https://doi.org/10.3390/catal15020180 - 14 Feb 2025

Viewed by 904

Abstract

Biocatalytic processes for the formation of bioactive compounds and biopolymer preparations that can be applied in pharmaceuticals and cosmetics are gaining increasing interest due to their safety and sustainability, relying on environmentally friendly approaches and biocompatible compounds. In this work, we investigate the [...] Read more.

Biocatalytic processes for the formation of bioactive compounds and biopolymer preparations that can be applied in pharmaceuticals and cosmetics are gaining increasing interest due to their safety and sustainability, relying on environmentally friendly approaches and biocompatible compounds. In this work, we investigate the implementation of various Deep Eutectic Solvents (DES) in the laccase-catalyzed oxidation of hydroxytyrosol (HT), aiming to produce its oligomer derivatives such as HT dimer and trimer. The composition of the reaction mixture in which the oligomers’ yield was the highest was 70% v/v Bet:PG (1:4 molar ratio). The oligomers formed were subsequently used for the non-enzymatic grafting of chitosan (CS) and the development of bioactive chitosan-based nanogels (NG). Grafted chitosan nanogels were prepared by ionic gelation using sodium tripolyphosphate (TPP) as a cross-linking agent. The functionalized chitosan was characterized using Fourier-Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy, while Scanning Electron Microscopy (SEM) was employed for nanogel characterization. Compared to unmodified chitosan nanogels, grafted chitosan nanogels exhibited almost ten-fold higher antioxidant activity and approximately 20% greater antibacterial activity. Full article

(This article belongs to the Special Issue Catalytic Procedures for the Synthesis of Pharmaceutical Active Compounds in Deep Eutectic Solvents)

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17 pages, 4382 KiB

Open AccessEditor’s ChoiceArticle

The Effect of the Pore Size of TiO₂ Aerogel on the Photocatalytic Decomposition of Formaldehyde

by Fenglei Sun, Xian Yue, Xianbo Yu, Yuqian Di, Hu Chen, Shuao Xie, Wei Han, Xiaoxue Xi, Wenjing Zhang, Hanyu Zou, Huaxin Li and Junhui Xiang

Catalysts 2025, 15(2), 171; https://doi.org/10.3390/catal15020171 - 12 Feb 2025

Cited by 1 | Viewed by 1122

Abstract

TiO₂ aerogels have been employed for the degradation of formaldehyde (HCHO) via the photocatalytic generation of reactive oxygen species (ROS) (O²⁻, ·OH), and its pore size plays a crucial role in affecting the decomposition efficiency. However, there remains a lack [...] Read more.

TiO₂ aerogels have been employed for the degradation of formaldehyde (HCHO) via the photocatalytic generation of reactive oxygen species (ROS) (O²⁻, ·OH), and its pore size plays a crucial role in affecting the decomposition efficiency. However, there remains a lack of a comprehensive understanding regarding the internal mechanisms underlying the influence of pore size on HCHO decomposition. In this study, we prepared TiO₂ aerogels by the sol–gel method, and added polyvinyl alcohol (PVA) to introduce flexible molecular chains for pore size regulation, and obtained anatase crystals after a heat treatment at 800 °C. The photocatalytic decomposition mechanism of HCHO was researched using TiO₂ aerogels with varying pore sizes as catalysts. The results indicated that the pore size of TiO₂ aerogels was one of the important factors for HCHO decomposition. We validated that the efficiency of HCHO decomposition was related to the oxygen pressure in the pores of the TiO₂ aerogel, and the oxygen pressure was inversely proportional to the pore size, then the pore size of the TiO₂ aerogel and the decomposition efficiency of HCHO were linked through the oxygen pressure. Finally, the optimal pore size of the TiO₂ aerogel for the photocatalytic HCHO decomposition was 2 nm–10 nm. The present study aims to establish the relationship and influence of the pore size of TiO₂ aerogels on the performance of photocatalytic decomposition and promoting further advancements in porous nanomaterials for catalysis. Full article

(This article belongs to the Special Issue Cutting-Edge Catalytic Strategies for Organic Pollutant Mitigation)

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24 pages, 3072 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Advances in Membrane Electrode Assembly Based Nitrate Reduction Electrolyzers for Sustainable Ammonia Synthesis

by Keon-Han Kim and Jeonghoon Lim

Catalysts 2025, 15(2), 172; https://doi.org/10.3390/catal15020172 - 12 Feb 2025

Cited by 1 | Viewed by 1756

Abstract

The electrochemical reduction from nitrate (NO₃RR) to ammonia (NH₃) provides a decentralized and environmentally friendly route for sustainable ammonia production while addressing the urgent issue of nitrate pollution in water bodies. Recent advancements in NO₃RR research have [...] Read more.

The electrochemical reduction from nitrate (NO₃RR) to ammonia (NH₃) provides a decentralized and environmentally friendly route for sustainable ammonia production while addressing the urgent issue of nitrate pollution in water bodies. Recent advancements in NO₃RR research have improved catalyst designs, mechanistic understanding, and electrolyzer technologies, enhancing selectivity, yield, and energy efficiency. This review explores cutting-edge developments, focusing on innovative designs for catalysts and electrolyzers, such as membrane electrode assemblies (MEA) and electrolyzer configurations, understanding the role of membranes in MEA designs, and various types of hybrid and membrane-free reactors. Furthermore, the integration of NO₃RR with anodic oxidation reactions has been demonstrated to improve overall efficiency by generating valuable co-products. However, challenges such as competitive hydrogen evolution, catalyst degradation, and scalability remain critical barriers to large-scale adoption. We provide a comprehensive overview of recent progress, evaluate current limitations, and identify future research directions for realizing the full potential of NO₃RR in sustainable nitrogen cycling and ammonia synthesis. Full article

(This article belongs to the Special Issue Electrocatalytic Nitrogen-Cycle)

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24 pages, 5999 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Unravelling Vacuum Gas Oil Catalytic Cracking: The Influence of the Catalyst-to-Oil Ratio on FCC Catalyst Performance

by Jansen Gabriel Acosta-López, José Luis Muñoz and Hugo de Lasa

Catalysts 2025, 15(2), 170; https://doi.org/10.3390/catal15020170 - 12 Feb 2025

Cited by 1 | Viewed by 1205

Abstract

This study evaluates the impact of the catalyst-to-oil (C/O) ratio in the 1 to 7 range on the catalytic cracking of vacuum gas oil (VGO). Experiments are conducted using fluid catalytic cracking (FCC)-type catalysts, in a mini-fluidized bench-scale Riser Simulator reactor invented at [...] Read more.

This study evaluates the impact of the catalyst-to-oil (C/O) ratio in the 1 to 7 range on the catalytic cracking of vacuum gas oil (VGO). Experiments are conducted using fluid catalytic cracking (FCC)-type catalysts, in a mini-fluidized bench-scale Riser Simulator reactor invented at the Chemical Reactor Engineering Centre (CREC), University of Western Ontario. The CREC Riser Simulator replicates FCC industrial operating conditions such as temperature, species partial pressure, and reaction times. The results indicate that increasing the C/O ratio above 5 slightly impacts VGO conversion, increases light gases yield, decreases light cycle oil (LCO) yield, and stabilizes gasoline yield. These findings align with temperature-programmed desorption (TPD) data, showing how the retention of a larger number of acid sites at a C/O of 7 boosts light gas production and reduces LCO selectivity. These elevated C/O ratios also lead to higher coke formation. The results reported together with future studies conducted by our research team on the impact of higher catalyst flows, larger potential catalyst attrition, higher catalyst loading in the cyclones, and excess heat generated in the catalyst regenerator unit, are of critical value for establishing the impact of C/O ratios in the overall FCC refinery operation. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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19 pages, 2934 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Advances in In Situ Investigations of Heterogeneous Catalytic Ammonia Synthesis

by Weiyi Su, Xi Cheng, Suokun Shang, Runze Pan, Miao Qi, Qinqin Sang, Zhen Xie, Honghua Zhang, Ke Wang and Yanrong Liu

Catalysts 2025, 15(2), 160; https://doi.org/10.3390/catal15020160 - 9 Feb 2025

Cited by 2 | Viewed by 1348

Abstract

Ammonia is a key “platform” raw chemical for fertilizers and nitrogen-containing chemicals, with a global annual production of ~180 million tons. Recently, ammonia has also come to be seen as an excellent hydrogen-containing liquid promising for long-term, large-scale hydrogen storage and transport. Therefore, [...] Read more.

Ammonia is a key “platform” raw chemical for fertilizers and nitrogen-containing chemicals, with a global annual production of ~180 million tons. Recently, ammonia has also come to be seen as an excellent hydrogen-containing liquid promising for long-term, large-scale hydrogen storage and transport. Therefore, artificial N₂ fixation, an ammonia synthesis reaction, will play a pivotal role influencing food and energy for human society. Till now, industrial ammonia synthesis has relied on high temperature and high pressure (420~500 °C, 10~15 MPa). Researchers are devoted to developing new catalysts as well as optimizing the traditional Fe-based catalysts continuously. However, the relation between the catalysts’ detailed structure and ammonia production efficiency are not yet fully understood, which is crucial to provide guidance on further improving the efficacy of this importance reaction. Recently, in situ characterization techniques have achieved significant improvements and new understandings have been achieved on the central topic of catalysis. In this review, recent advances in in situ investigations of heterogeneous catalytic ammonia synthesis are summarized and the key results are discussed. In the end, a concluding remark and perspective are proposed, with the hope of inspiring future investigations dedicated to unveiling the principles of designing catalysts for ammonia synthesis. Full article

(This article belongs to the Special Issue Applications of Heterogeneous Catalysts in Green Chemistry, 2nd Edition)

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25 pages, 18185 KiB

Open AccessEditor’s ChoiceArticle

On the Conceptualization of the Active Site in Selective Oxidation over a Multimetal Oxide Catalyst: From Atomistic to Black-Box Approximation

by José F. Durán-Pérez, José G. Rivera de la Cruz, Martín Purino, Julio C. García-Martínez and Carlos O. Castillo-Araiza

Catalysts 2025, 15(2), 144; https://doi.org/10.3390/catal15020144 - 4 Feb 2025

Viewed by 1094

Abstract

Catalytic reactor engineering bridges the active-site scale and the industrial-reactor scale, with kinetics as the primary bottleneck in scale-up. The main challenge in kinetics is conceptualizing the active site and formulating the reaction mechanism, leading to multiple approaches without clear guidance on their [...] Read more.

Catalytic reactor engineering bridges the active-site scale and the industrial-reactor scale, with kinetics as the primary bottleneck in scale-up. The main challenge in kinetics is conceptualizing the active site and formulating the reaction mechanism, leading to multiple approaches without clear guidance on their reliability for industrial-reactor design. This work assesses different approaches to active-site conceptualization and reaction-mechanism formulation for selective oxidation over a complex multi-metal catalyst. It integrates atomistic-scale insights from periodic Density Functional Theory (DFT) calculations into kinetic-model development. This approach contrasts with the macroscopic classical method, which treats the catalyst as a black box, as well as with alternative atomistic methods that conceptualize the active site as a single metal atom on different catalytic-surface regions. As a case study, this work examines ethane oxidative dehydrogenation to ethylene over the multi-metal oxide catalyst MoVTeNbO, which has a complex structure. This analysis provides insights into the ability of DFT to accurately describe reactions on such materials. Additionally, it compares DFT predictions to experimental data obtained from a non-idealized MoVTeNbO catalyst synthesized and assessed under kinetic control at the laboratory scale. The findings indicate that while the black-box active-site conceptualization best describes observed trends, its reaction mechanism and parameters lack reliability compared to DFT calculations. Furthermore, atomistic active-site conceptualizations lead to different parameter sets depending on how the active site and reaction mechanism are defined. Unlike previous studies, our approach determines activation-energy profiles within the range predicted by DFT. The resulting kinetic model describes experimental trends while maintaining phenomenological and statistical reliability. The corrections required for primary parameters remain below 20 kJ mol

^{- 1}

, consistent with the inherent uncertainties in DFT calculations. In summary, this work demonstrates the feasibility of integrating atomistic insights into kinetic modeling, offering different perspectives on active-site conceptualization and reaction-mechanism formulation, paving the way for future studies on rational catalyst and industrial-reactor design. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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36 pages, 6968 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Protein Engineering for Industrial Biocatalysis: Principles, Approaches, and Lessons from Engineered PETases

by Konstantinos Grigorakis, Christina Ferousi and Evangelos Topakas

Catalysts 2025, 15(2), 147; https://doi.org/10.3390/catal15020147 - 4 Feb 2025

Cited by 4 | Viewed by 4016

Abstract

Protein engineering has emerged as a transformative field in industrial biotechnology, enabling the optimization of enzymes to meet stringent industrial demands for stability, specificity, and efficiency. This review explores the principles and methodologies of protein engineering, emphasizing rational design, directed evolution, semi-rational approaches, [...] Read more.

Protein engineering has emerged as a transformative field in industrial biotechnology, enabling the optimization of enzymes to meet stringent industrial demands for stability, specificity, and efficiency. This review explores the principles and methodologies of protein engineering, emphasizing rational design, directed evolution, semi-rational approaches, and the recent integration of machine learning. These strategies have significantly enhanced enzyme performance, even rendering engineered PETase industrially relevant. Insights from engineered PETases underscore the potential of protein engineering to tackle environmental challenges, such as advancing sustainable plastic recycling, paving the way for innovative solutions in industrial biocatalysis. Future directions point to interdisciplinary collaborations and the integration of emerging machine learning technologies to revolutionize enzyme design. Full article

(This article belongs to the Special Issue Feature Review Papers in Biocatalysis and Enzyme Engineering)

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34 pages, 6093 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Cobalt Decarbonization Catalysts Turning Methane to Clean Hydrogen and Valuable Carbon Nanostructures: A Review

by Elpida Zeza, Eleni Pachatouridou, Angelos A. Lappas and Eleni F. Iliopoulou

Catalysts 2025, 15(2), 145; https://doi.org/10.3390/catal15020145 - 4 Feb 2025

Viewed by 2050

Abstract

The continuous growth in world energy demands along with the urgent need for decarbonization are strong motivations for the development and usage of sustainable fuels. Hydrogen is highly anticipated to replace fossil fuels in energy production, as it is one of the cleanest [...] Read more.

The continuous growth in world energy demands along with the urgent need for decarbonization are strong motivations for the development and usage of sustainable fuels. Hydrogen is highly anticipated to replace fossil fuels in energy production, as it is one of the cleanest energy sources with high energy density per weight. Among the hydrogen production methods, catalytic methane pyrolysis (CMP) stands out as it can contribute to the decarbonization process, since the only co-products include valuable carbon structures and no greenhouse emissions. Cobalt has been shown to be a competent metallic catalytic material with high activity in relation to hydrogen production and selectivity towards valuable carbon nanotubes (CNTs), or carbon nanofibers (CNFs). This review article aims to offer insights relevant to future developments in CMP, by reporting the advantages of methane decomposition over cobalt catalysts. It provides a summary of the factors that influence both hydrogen yield and carbon growth. More specifically, the impacts of different metal loadings and the benefits of utilizing both support carriers and bimetallic systems are addressed. Last but not least, the findings on the most efficient preparation procedures and the optimum operating conditions are also revealed, as supported by published experimental data. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Catalytic Materials)

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20 pages, 5440 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Novel Ni/SBA-15 Catalyst Pellets for Tar Catalytic Cracking in a Dried Sewage Sludge Pyrolysis Pilot Plant

by Emmanuel Iro, Saeed Hajimirzaee, Takehiko Sasaki and Maria Olea

Catalysts 2025, 15(2), 142; https://doi.org/10.3390/catal15020142 - 3 Feb 2025

Viewed by 1087

Abstract

Novel Ni/SBA-15 catalysts were synthesised and their activity in the dry reforming of methane process was assessed. These materials were prepared into extrudates shaped like pellets and tested in a pyrolysis pilot plant fitted with a catalytic reactor for sewage sludge pyrolysis tar [...] Read more.

Novel Ni/SBA-15 catalysts were synthesised and their activity in the dry reforming of methane process was assessed. These materials were prepared into extrudates shaped like pellets and tested in a pyrolysis pilot plant fitted with a catalytic reactor for sewage sludge pyrolysis tar removal. The Ni/SBA-15 catalyst pellets remained highly active and stable throughout the test’s duration, converting 100% tar in the hot gas to smaller non-condensable gases, thereby increasing the pyrolysis gas fraction and eliminating the problematic tar in the vapour stream. Catalyst characterisation with Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray (EDX) analysis, Transmission Electron Microscopy (TEM), and Thermogravimetric Analysis (TGA) confirmed that both the Ni/SBA-15-powered catalyst and the pellets were resistant to sintering and carbon deposition and remained highly active even with relatively high-level sulphur in the feed stream. The Ni/SBA-15 catalyst extrudates were prepared by mixing the powdered catalyst with varied amounts of colloidal silica binder and fixed amounts of methyl cellulose and water. The highest mechanical strength of the extrudates was determined to be of those obtained with 36% of the inorganic binder. The physical properties and catalytic activity of Ni/SBA-15 pellets with 36% colloidal silica were compared with the original powdered Ni/SBA-15 catalyst to assess the binder inhibitory effect, if any. The results confirmed that colloidal silica binder did not inhibit the desired catalyst properties and performance in the reaction. Instead, enhanced catalytic performance was observed. Full article

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

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15 pages, 2440 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Synergistic Effects of Photocatalysis, Ozone Treatment, and Metal Catalysts on the Decomposition of Acetaldehyde

by Tsuyoshi Ochiai, Kengo Hamada and Michifumi Okui

Catalysts 2025, 15(2), 141; https://doi.org/10.3390/catal15020141 - 3 Feb 2025

Viewed by 1800

Abstract

This study explores the synergistic interactions between photocatalysis, ozone treatment, and metal catalysts in the decomposition of acetaldehyde, a representative volatile organic compound (VOC). The study addresses the growing need for efficient air purification technologies by integrating advanced oxidation processes. Metal catalysts, particularly [...] Read more.

This study explores the synergistic interactions between photocatalysis, ozone treatment, and metal catalysts in the decomposition of acetaldehyde, a representative volatile organic compound (VOC). The study addresses the growing need for efficient air purification technologies by integrating advanced oxidation processes. Metal catalysts, particularly manganese oxide-based materials, were combined with photocatalysis and ozonation to investigate their impact on acetaldehyde removal efficiency. Experimental results revealed that the treatment integrating these methods significantly outperformed conventional single-process treatments. Metal catalysts facilitated the initial oxidation of acetaldehyde, while photocatalysis accelerated subsequent stages, including the mineralisation of intermediates. Ozone contributed additional reactive oxidative species, further enhancing decomposition rates. These findings provide valuable insights into the design of efficient VOC removal systems, demonstrating that integrating metal catalysts with photocatalytic and ozonation processes offers a promising strategy for improving air purification technologies. This approach has potential applications in environmental remediation and indoor air quality management. Full article

(This article belongs to the Special Issue TiO₂ Photocatalysts: Design, Optimization and Application)

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17 pages, 1528 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Innovative Production of 3D-Printed Ceramic Monolithic Catalysts for Oxidation of VOCs by Using Fused Filament Fabrication

by Filip Car, Nikolina Zekić, Domagoj Vrsaljko and Vesna Tomašić

Catalysts 2025, 15(2), 125; https://doi.org/10.3390/catal15020125 - 27 Jan 2025

Viewed by 1717

Abstract

In this work, ceramic monolithic catalyst carriers based on zirconium dioxide (ZrO₂) were produced using fused filament fabrication (FFF). The active catalyst components were deposited on the resulting carriers using the wet impregnation method. The activity of the prepared monolithic catalysts [...] Read more.

In this work, ceramic monolithic catalyst carriers based on zirconium dioxide (ZrO₂) were produced using fused filament fabrication (FFF). The active catalyst components were deposited on the resulting carriers using the wet impregnation method. The activity of the prepared monolithic catalysts was evaluated by catalytic oxidation of a mixture of aromatic volatile organic compounds: benzene, toluene, ethylbenzene, and o-xylene (BTEX). The efficiency of the prepared monolithic catalysts was investigated as a function of the geometry of the monolithic carrier (ZDP, Z, and M) and the chemical composition of the catalytically active component (MnFeO_x, MnCuO_x, and MnNiO_x) during the catalytic oxidation of BTEX compounds. The mechanical stability of the catalyst layer and the dimensional stability of the 3D-printed monolithic catalyst carriers were investigated prior to the kinetic measurements. In addition, thorough characterization of the commercial ZrO₂-based filament was carried out. The results of the efficiency of the prepared monolithic catalysts for the catalytic oxidation of BTEX showed that the 3D-printed model M, which contained MnFeO_x as the catalytically active component, was the most successful catalyst for the oxidation of BTEX compounds. The mentioned catalyst enables the catalytic oxidation of all components of the BTEX mixture (>99% efficiency) at a temperature of 177 °C. Full article

(This article belongs to the Special Issue Advances in Catalysis for a Sustainable Future)

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20 pages, 6022 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Nitrogen/Sulfur Co-Doped Biochar for Peroxymonosulfate Activation in Paracetamol Degradation: Mechanism Insight and Toxicity Evaluation

by Jiaqi Cui, Hong Meng, Yu Chen, Yongqing Zhang, Waseem Hayat and Charles Q. Jia

Catalysts 2025, 15(2), 121; https://doi.org/10.3390/catal15020121 - 26 Jan 2025

Cited by 1 | Viewed by 1203

Abstract

Advanced oxidation processes based on either peroxydisulfate (PDS) or peroxymonosulfate (PMS), collectively termed persulfate-based advanced oxidation processes (PS-AOPs), show potential in wastewater treatment applications. In this work, the nitrogen (N) and sulfur (S) co-doped biochar (NSBC) was prepared via a one-step pyrolysis of [...] Read more.

Advanced oxidation processes based on either peroxydisulfate (PDS) or peroxymonosulfate (PMS), collectively termed persulfate-based advanced oxidation processes (PS-AOPs), show potential in wastewater treatment applications. In this work, the nitrogen (N) and sulfur (S) co-doped biochar (NSBC) was prepared via a one-step pyrolysis of coffee grounds at 400 to 800 °C as a PMS activator for degrading paracetamol (PCT). The non-metallic NSBC demonstrated exceptional catalytic activity in activating PMS. In the NSBC-800/PMS system, 100% of PCT was completely degraded within 20 min, with a high reaction rate constant (k_obs) of 0.2412 min⁻¹. The system’s versatility was highlighted by its degradation potential across a wide pH range (3–11) and in the presence of various background ions and humic acids. The results of various experiments and characterization techniques showed that the system relied on an NSBC-800-mediated electron transfer as the main mechanism for PCT degradation. Additionally, there was a minor involvement of ¹O₂ in a non-radical degradation pathway. The graphitic N and thiophene-S (C-S-C) moieties introduced by N/S co-doping, as well as the carbonyl (C=O) groups of the biochar, were considered active sites promoting ¹O₂ generation. The total organic carbon (TOC) removal rate reached 37% in 120 min, while the assessment of the toxicity of the degradation products also affirmed the system’s environmental safety. This research provides a novel method for preparing environmentally friendly and cost-effective carbon-based catalysts for environmental remediation. Full article

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20 pages, 6075 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Photocatalysis by Mixed Oxides Containing Niobium, Vanadium, Silica, or Tin

by Agnieszka Feliczak-Guzik, Agata Wawrzyńczak and Izabela Nowak

Catalysts 2025, 15(2), 118; https://doi.org/10.3390/catal15020118 - 26 Jan 2025

Viewed by 783

Abstract

Nb-Sn, V-Sn mixed-metal oxides and Nb-Si, V-Si metal oxide–silicas were successfully synthesized through a “soft” templating method, in which appropriate amounts of metal salts (either niobium(V) chloride, or vanadium(IV) oxide sulfate hydrate or tin(II) chloride dihydrate) or tetraethyl orthosilicate (TEOS) were mixed with [...] Read more.

Nb-Sn, V-Sn mixed-metal oxides and Nb-Si, V-Si metal oxide–silicas were successfully synthesized through a “soft” templating method, in which appropriate amounts of metal salts (either niobium(V) chloride, or vanadium(IV) oxide sulfate hydrate or tin(II) chloride dihydrate) or tetraethyl orthosilicate (TEOS) were mixed with hexadecyltrimethylammonium chloride (HDTA) or sodium dodecyl sulfate (SDS) solutions to obtain a new series of mesoporous oxides, followed by calcination at different temperatures. As-obtained samples were characterized by SEM, TEM, XRD, and UV-Vis spectra techniques. The photocatalytic activities of the samples were evaluated by degradation of methyl orange II (MO) under simulated sunlight irradiation. The effects of metal species and calcination temperature on the physicochemical characteristic and photocatalytic activity of the samples were investigated in detail. The results indicated that, compared to pure oxides, mixed-metal oxide showed superior photocatalytic performance for the degradation of MO. A maximum photocatalytic discoloration rate of 97.3% (with MO initial concentration of 0.6·10⁻⁴ mol/dm³) was achieved in 300 min with the NbSiOx material, which was much higher than that of Degussa P25 under the same conditions. Additionally, the samples were tested in the photochemical oxidation process, i.e., advanced oxidation processes (AOPs) to treat the commercial non-ionic surfactant: propylene oxide ethylene oxide polymer mono(nonylphenyl) ether (N8P7, PCC Rokita). A maximum of 99.9% photochemical degradation was achieved in 30 min with the NbSiOx material. Full article

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37 pages, 12778 KiB

Open AccessEditor’s ChoiceReview

A Review of the Application of Metal-Based Heterostructures in Lithium–Sulfur Batteries

by Yichao Luo, Zhen Zhang, Yaru Wang, Yalong Zheng, Xinyu Jiang, Yan Zhao, Yi Zhang, Xiang Liu, Zhoulu Wang and Baizeng Fang

Catalysts 2025, 15(2), 106; https://doi.org/10.3390/catal15020106 - 22 Jan 2025

Cited by 2 | Viewed by 1512

Abstract

Lithium–sulfur (Li-S) batteries are recognized as a promising alternative in the energy storage domain due to their high theoretical energy density, environmental friendliness, and cost-effectiveness. However, challenges such as polysulfide dissolution, the low conductivity of sulfur, and limited cycling stability hinder their widespread [...] Read more.

Lithium–sulfur (Li-S) batteries are recognized as a promising alternative in the energy storage domain due to their high theoretical energy density, environmental friendliness, and cost-effectiveness. However, challenges such as polysulfide dissolution, the low conductivity of sulfur, and limited cycling stability hinder their widespread application. To address these issues, the incorporation of heterostructured metallic substrates into Li-S batteries has emerged as a pivotal strategy, enhancing electrochemical performance by facilitating better adsorption and catalysis. This review delineates the modifications made to the cathode and separator of Li-S batteries through metallic heterostructures. We categorize the heterostructures into three classifications: single metals and metal compounds, MXene materials paired with metal compounds, and heterostructures formed entirely of metal compounds. Each category is systematically examined for its contributions to the electrochemical behavior and efficiency of Li-S batteries. The performance of these heterostructures is evaluated in both the cathode and separator contexts, revealing significant improvements in lithium-ion conductivity and polysulfide retention. Our findings suggest that the strategic design of metallic heterostructures can not only mitigate the inherent limitations of Li-S batteries but also pave the way for the development of high-performance energy storage systems. Full article

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

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34 pages, 2388 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Biocatalysis for Lignin Conversion and Valorization: Driving Sustainability in the Circular Economy

by Parushi Nargotra, Vishal Sharma, Hui-Min David Wang, Chwen-Jen Shieh, Yung-Chuan Liu and Chia-Hung Kuo

Catalysts 2025, 15(1), 91; https://doi.org/10.3390/catal15010091 - 20 Jan 2025

Cited by 5 | Viewed by 2556

Abstract

In recent years, lignin derived from lignocellulosic biomass has emerged as a critical component in modern biorefinery systems. The production yield and reactivity of lignin are critical factors for advancing the research and development of lignin-derived biochemicals. The recovery of high-purity lignin, along [...] Read more.

In recent years, lignin derived from lignocellulosic biomass has emerged as a critical component in modern biorefinery systems. The production yield and reactivity of lignin are critical factors for advancing the research and development of lignin-derived biochemicals. The recovery of high-purity lignin, along with carbohydrates, is accomplished through the application of various advanced pretreatment techniques. However, biological pretreatment using lignin-degrading enzymes to facilitate lignin depolymerization is an environmentally benign method for the sustainable production of valuable products that occurs under mild conditions with high substrate specificity. The current review presents the role of biocatalysis in lignin valorization, focusing on lignin-degrading enzymes that facilitate different bond cleavage in the lignocellulosic biomass. The review also highlights the recent advancements in enzyme engineering that have enabled the enhancement of enzyme stability and catalytic efficiency for improving lignin valorization processes. Furthermore, the integration of omics technologies that provide valuable insights into the microbial and enzymatic pathways involved in lignin degradation is presented. The challenges and future prospects in this emerging field of study for a biorefinery concept are also outlined for improving lignin depolymerization efficiency. Full article

(This article belongs to the Special Issue Enzyme and Biocatalysis Application)

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20 pages, 3426 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

IrO_x Supported on Submicron-Sized Anatase TiO₂ as a Catalyst for the Oxygen Evolution Reaction

by Josep Boter-Carbonell, Carlos Calabrés-Casellas, Maria Sarret, Teresa Andreu and Pere L. Cabot

Catalysts 2025, 15(1), 79; https://doi.org/10.3390/catal15010079 - 16 Jan 2025

Cited by 1 | Viewed by 1111

Abstract

Ir-based catalysts are the best in terms of activity and stability for oxygen evolution reactions (OERs) in proton exchange water electrolysis. Due to their cost, efforts have been made to decrease their load without a loss of activity. In this paper, Ir nanoparticles [...] Read more.

Ir-based catalysts are the best in terms of activity and stability for oxygen evolution reactions (OERs) in proton exchange water electrolysis. Due to their cost, efforts have been made to decrease their load without a loss of activity. In this paper, Ir nanoparticles measuring 2–3 nm were loaded on TiO₂ anatase supports of submicrometric size in different amounts using the microwave polyol method to optimize their mass activity. Using anatase particles with a diameter of about 100 nm and titania nanotubes (TNTs), Ir/TiO₂ catalysts with Ir contents of 5, 10, 20, and 40 wt.% were synthesized and characterized via structural and electrochemical techniques. It was shown that the amount of Ir must be regulated to obtain continuous coverage on titania with strong Ir–TiO₂ interactions which, for the 100 nm diameter anatase, is limited to about 20 wt.%. A higher percentage of Ir over 40 wt.% can be dispersed over the TNTs. Exceeding one layer of coverage leads to a decrease in the catalyst’s utilization. Ir/TiO₂(10:90), Ir/TiO₂(20:80), and Ir/TiO₂(40:60) presented the highest pseudocapacitive currents per unit of Ir mass. The electrochemical active areas and mass activities for these later catalysts were also the highest compared to Ir/TiO₂(05:95), Ir/TNT(40:60), and the unsupported catalysts and increased from 40 to 10 wt.% Ir. They also presented the lowest overpotentials of about 300 mV at 10 mA cm⁻² for the OER, with Ir/TiO₂(10:90) presenting the best specific activities and surface turnover frequencies, thus showing that the size of the support can be regulated to decrease the Ir content of the catalyst without a loss of activity. Full article

(This article belongs to the Special Issue Electrocatalytic Water Oxidation, 2nd Edition)

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23 pages, 5165 KiB

Open AccessEditor’s ChoiceReview

Research Progress in Photocatalytic-Coupled Microbial Electrochemical Technology in Wastewater Treatment

by Qianhao Zeng, Wenhui An, Dongxiao Peng, Qiting Liu, Xu Zhang, Haiyu Ge and Hongbo Liu

Catalysts 2025, 15(1), 81; https://doi.org/10.3390/catal15010081 - 16 Jan 2025

Cited by 3 | Viewed by 1523

Abstract

Photocatalytic-coupled microbial electrochemical systems (MESs) represent an emerging wastewater treatment technology which aims to address the limitations of traditional methods, such as the inadequate removal of refractory pollutants and excessive energy consumption. This technology realizes the simultaneous degradation of refractory pollutants in wastewater [...] Read more.

Photocatalytic-coupled microbial electrochemical systems (MESs) represent an emerging wastewater treatment technology which aims to address the limitations of traditional methods, such as the inadequate removal of refractory pollutants and excessive energy consumption. This technology realizes the simultaneous degradation of refractory pollutants in wastewater and bioenergy recovery, demonstrating significant potential for development. However, the practical application of this technology is currently hindered by challenges including insufficient electrical power output, poor stability of photoelectric electrodes, and the design of amplified application systems. This review comprehensively examines the common coupling methods and principles of photocatalytic-coupled microbial electrochemical systems. Compared to previous studies, it provides a detailed analysis of the optimal configurations for treating wastewater containing various components, such as recalcitrant organic compounds, heavy metals, and nitrates, to achieve maximum efficiency. Moreover, it summarizes the synergistic effects observed between photocatalysis and MES that enhance the degradation efficiency of pollutants through various pathways, including increasing the potential difference of cytochromes, promoting the formation of conductive nanowires, accelerating the electron transfer rates, and inhibiting electron–hole recombination. Finally, this review highlights the challenges in practical applications and proposes future research directions to facilitate the further development of this technology. Full article

(This article belongs to the Special Issue Environmental Catalysis: Special Topic on Microbial Fuel Cell and Wastewater Treatment)

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11 pages, 1397 KiB

Open AccessEditor’s ChoiceArticle

Effects of Enzymatic Disintegration on the Decomposition of Organic Compounds During Methane Fermentation of Sewage Sludge

by Bartłomiej Macherzyński

Catalysts 2025, 15(1), 75; https://doi.org/10.3390/catal15010075 - 15 Jan 2025

Cited by 1 | Viewed by 994

Abstract

This paper presents the results of a study on the effect of lipase on the methane fermentation of sewage sludge. The process was conducted at 37 °C for 20 days for five sludge mixtures. Excess sludge inoculated with digested sludge constituted the control [...] Read more.

This paper presents the results of a study on the effect of lipase on the methane fermentation of sewage sludge. The process was conducted at 37 °C for 20 days for five sludge mixtures. Excess sludge inoculated with digested sludge constituted the control sample. The other four samples are the aforementioned mixtures with the addition of lipase in amounts representing 0, 1, 2, 3, and 4% (w/w) with respect to sludge dry weight. The organic matter decomposition rate was 27.1% in the control sludge and from 33.5 to 46.7% in the disintegrated sludge. During the digestion of the control sludge, the total amount of biogas was 5802 mL·L⁻¹. In sewage sludge enzymatically disintegrated by lipase, there was an increase in biogas from 15 to 26%. In the disintegrated sludge, an almost complete (95–100%) reduction in E. coli and Salmonella spp. was achieved. Therefore, enzymatic disintegration can be an effective alternative to physical and chemical disintegration methods. Full article

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

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21 pages, 5975 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Palladium-Catalyzed Cascade Reactions for Synthesis of Heterocycles Initiated by C(sp³)–H Functionalization

by Dan Yuan, Ziting Xu, Yang Zhou, Faith Herington, Chong Liu, Ke Yang and Haibo Ge

Catalysts 2025, 15(1), 72; https://doi.org/10.3390/catal15010072 - 14 Jan 2025

Cited by 2 | Viewed by 1221

Abstract

Heterocycles are widely present in natural products, pharmaceuticals, and organic functional materials. In heterocycle synthesis, Pd-catalyzed cascade C–H functionalization has been regarded as one of the most powerful approaches due to its advantages in terms of high atom efficiency and readily available starting [...] Read more.

Heterocycles are widely present in natural products, pharmaceuticals, and organic functional materials. In heterocycle synthesis, Pd-catalyzed cascade C–H functionalization has been regarded as one of the most powerful approaches due to its advantages in terms of high atom efficiency and readily available starting materials. In this review, we will briefly introduce the major advances in palladium-catalyzed cascade C(sp³)–H activation and annulation for constructing different types of heterocycles through inter- and intramolecular pathways from 2010 to 2023. Full article

(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)

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13 pages, 5100 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Solid-State Reaction Synthesis of CoSb₂O₆-Based Electrodes Towards Oxygen Evolution Reaction in Acidic Electrolytes: Effects of Calcination Time and Temperature

by Francesco Vanzetti, Hilmar Guzmán and Simelys Hernández

Catalysts 2025, 15(1), 68; https://doi.org/10.3390/catal15010068 - 13 Jan 2025

Viewed by 1056

Abstract

Mitigating global warming necessitates transitioning from fossil fuels to alternative energy carriers like hydrogen. Efficient hydrogen production via electrocatalysis requires high-performance, stable anode materials for the oxygen evolution reaction (OER) to support the hydrogen evolution reaction (HER) at the cathode. Developing noble metal-free [...] Read more.

Mitigating global warming necessitates transitioning from fossil fuels to alternative energy carriers like hydrogen. Efficient hydrogen production via electrocatalysis requires high-performance, stable anode materials for the oxygen evolution reaction (OER) to support the hydrogen evolution reaction (HER) at the cathode. Developing noble metal-free electrocatalysts is therefore crucial, particularly for acidic electrolytes, to avoid reliance on scarce and expensive metals such as Ir and Ru. This study investigates a low-cost, solvent-free solid-state synthesis of CoSb₂O₆, focusing on the influence of calcination time and temperature. Six samples were prepared and characterized using powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) analysis, field-emission scanning electron microscopy (FESEM), and electrochemical techniques. A non-pure CoSb₂O₆ phase was observed across all samples. Electrochemical testing revealed good short-term stability; however, all samples exhibited Tafel slopes exceeding 200 mV dec⁻¹ and overpotentials greater than 1 V. The sample calcined at 600 °C for 6 h showed the best performance, with the lowest Tafel slope and overpotential, attributed to its high CoSb₂O₆ content and maximized {110} facet exposure. This work highlights the role of calcination protocols in developing Co-based OER catalysts and offers insights for enhancing their electrocatalytic properties. Full article

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

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20 pages, 1692 KiB

Open AccessEditor’s ChoiceReview

The Organic-Functionalized Silica Nanoparticles as Lipase Carriers for Biocatalytic Application: Future Perspective in Biodegradation

by Jelena Milovanović, Katarina Banjanac, Jasmina Nikolić, Jasmina Nikodinović-Runić and Nevena Ž. Prlainović

Catalysts 2025, 15(1), 54; https://doi.org/10.3390/catal15010054 - 9 Jan 2025

Cited by 2 | Viewed by 1536

Abstract

Over the past three decades, organic reactions catalyzed by lipase have been extensively studied. To overcome the drawbacks of free enzymes and develop new and sustainable biocatalysts, various insoluble forms of lipases were examined. Especially interesting are lipases immobilized on silica nanoparticles (SiNPs) [...] Read more.

Over the past three decades, organic reactions catalyzed by lipase have been extensively studied. To overcome the drawbacks of free enzymes and develop new and sustainable biocatalysts, various insoluble forms of lipases were examined. Especially interesting are lipases immobilized on silica nanoparticles (SiNPs) due to their promising unique and advantageous physicochemical properties. Therefore, the present paper presents an overview of different organic functionalization methods of SiNP surfaces to create a more favorable microenvironment for lipase molecules. Given the high commercial value of lipases in biotechnological applications, the second part of this paper highlights the key industrial sectors utilizing these nanobiocatalysts. This review discusses the key industrial applications of silica-based lipase nanobiocatalysts, including biodiesel production, flavor ester synthesis, and pharmaceutical applications such as racemization. Special attention is given to emerging technologies, particularly the use of immobilized lipases in polymer biodegradation and polymerization reactions. These advances have paved the way for innovative solutions, such as self-degrading bioplastics, which hold significant promise for sustainable materials and environmental protection. This comprehensive overview underscores the transformative potential of lipase–SiNP nanobiocatalysts in both industrial and environmental contexts. Full article

(This article belongs to the Special Issue Feature Review Papers in Biocatalysis and Enzyme Engineering)

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23 pages, 3935 KiB

Open AccessEditor’s ChoiceArticle

Metal Foam as Surface-Extended Catalyst Support Structure for Process Intensification in the Dehydrogenation of Perhydro-Dibenzyltoluene on a Pt/Al₂O₃ Catalyst

by Kyatsinge Cedric Musavuli, Phillimon Modisha, Raymond Cecil Everson, Alexander Malakhov and Dmitri Bessarabov

Catalysts 2025, 15(1), 44; https://doi.org/10.3390/catal15010044 - 6 Jan 2025

Cited by 2 | Viewed by 1024

Abstract

Dibenzyltoluene/perhydro-dibenzyltoluene (H₀DBT/H₁₈DBT) is considered a promising liquid organic hydrogen carrier (LOHC) pair for the storage and transportation of green hydrogen (H₂). However, at the point of use, the catalytic dehydrogenation of H₁₈DBT is still limited [...] Read more.

Dibenzyltoluene/perhydro-dibenzyltoluene (H₀DBT/H₁₈DBT) is considered a promising liquid organic hydrogen carrier (LOHC) pair for the storage and transportation of green hydrogen (H₂). However, at the point of use, the catalytic dehydrogenation of H₁₈DBT is still limited by mass transport limitations. To address this issue, the dehydrogenation of H₁₈DBT was successfully conducted on Pt/Al₂O₃-coated foams in both an unstirred tank reactor and a fixed-bed reactor (FBR). A performance comparison between coated foams and pellets in the tank reactor revealed that H₂ productivities were 12–59% higher in the foam-based reactor than in the pellet-based reactor. Since the textural properties of the foam-supported and pellet-based catalysts were similar, the higher degree of dehydrogenation (DoD) and H₂ productivity achieved by the former were attributed to the geometric properties of the foam structure. Long-term tests performed in the FBR demonstrated the ability of the coated foams to maintain steady activity for >16 h on stream. However, the single-pass DoDs achieved were 34–38%. By recycling the partially dehydrogenated products three times into the FBR, the DoD improved to 63%. The results of this study demonstrated the capabilities of the coated foams in the process intensification of LOHC dehydrogenation reactors. Full article

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

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14 pages, 6154 KiB

Open AccessEditor’s ChoiceArticle

Xanthan Gum and Microcrystalline Cellulose as Stabilizers in Emulsions Containing Catalytically Modified Animal and Vegetable Fat

by Małgorzata Kowalska, Magdalena Wozniak, Anna Zbikowska, Jakub Okolus and Artur Molik

Catalysts 2025, 15(1), 41; https://doi.org/10.3390/catal15010041 - 5 Jan 2025

Cited by 1 | Viewed by 1332

Abstract

The aim of this study was to design model emulsion systems based on enzymatic modification fats for shaping the quality of target products in the food, cosmetic, and pharmaceutical industries. In this study, a catalysis process carried out in the presence of immobilized [...] Read more.

The aim of this study was to design model emulsion systems based on enzymatic modification fats for shaping the quality of target products in the food, cosmetic, and pharmaceutical industries. In this study, a catalysis process carried out in the presence of immobilized lipase as a catalyst was used to obtain the fatty mixtures constituting the fat base of the emulsions. It was assumed to produce stable emulsion products containing modified fat with a sufficient amount of emulsifiers and a variable concentration of a viscosity modifier, which was a mixture of xanthan gum and microcrystalline cellulose (XGMCC). The following methods were used in the evaluation of emulsions: evaluation of the stability of systems using the Turbiscan test, evaluation of average particle size, microscopic evaluation of emulsions, and evaluation of texture and viscosity. Based on the results obtained for XGMCC-stabilized emulsion systems containing enzymatically modified fats, it was found that some of the systems had satisfactory stability. No correlation was observed between the applied concentration of a texture modifier and emulsion stability. However, the type of fatty phase used influenced the stability of the analyzed systems. Taking the above relationship into account, emulsion E67, which was characterized by a small degree of destabilization changes, was evaluated as the best system. This emulsion was characterized by the lowest droplet diameter of the dispersed phase at all measuring points during the storage process. This system can be used as a stable model system as a starting point in the development of a new food or cosmetic formulation. Full article

(This article belongs to the Section Biocatalysis)

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27 pages, 1438 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Metal-Based Catalysts in Biomass Transformation: From Plant Feedstocks to Renewable Fuels and Chemicals

by Muhammad Saeed Akhtar, Muhammad Tahir Naseem, Sajid Ali and Wajid Zaman

Catalysts 2025, 15(1), 40; https://doi.org/10.3390/catal15010040 - 4 Jan 2025

Cited by 6 | Viewed by 2605

Abstract

The transformation of biomass into renewable fuels and chemicals has gained remarkable attention as a sustainable alternative to fossil-based resources. Metal-based catalysts, encompassing transition and noble metals, are crucial in these transformations as they drive critical reactions, such as hydrodeoxygenation, hydrogenation, and reforming. [...] Read more.

The transformation of biomass into renewable fuels and chemicals has gained remarkable attention as a sustainable alternative to fossil-based resources. Metal-based catalysts, encompassing transition and noble metals, are crucial in these transformations as they drive critical reactions, such as hydrodeoxygenation, hydrogenation, and reforming. Transition metals, including nickel, cobalt, and iron, provide cost-effective solutions for large-scale processes, while noble metals, such as platinum and palladium, exhibit superior activity and selectivity for specific reactions. Catalytic advancements, including the development of hybrid and bimetallic systems, have further improved the efficiency, stability, and scalability of biomass transformation processes. This review highlights the catalytic upgrading of lignocellulosic, algal, and waste biomass into high-value platform chemicals, biofuels, and biopolymers, with a focus on processes, such as Fischer–Tropsch synthesis, aqueous-phase reforming, and catalytic cracking. Key challenges, including catalyst deactivation, economic feasibility, and environmental sustainability, are examined alongside emerging solutions, like AI-driven catalyst design and lifecycle analysis. By addressing these challenges and leveraging innovative technologies, metal-based catalysis can accelerate the transition to a circular bioeconomy, supporting global efforts to combat climate change and reduce fossil fuel dependence. Full article

(This article belongs to the Special Issue Catalytic Conversion of Biomass to Chemicals)

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19 pages, 3854 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

One-Step Ball Milling Synthesis of Zr-Based Mixed Oxides for the Catalytic Study of Methyl Levulinate Conversion into γ-Valerolactone Under Microwave Irradiation

by Noelia Lázaro, Marina Ronda-Leal, Carolina Vargas, Weiyi Ouyang and Antonio Pineda

Catalysts 2025, 15(1), 35; https://doi.org/10.3390/catal15010035 - 3 Jan 2025

Viewed by 1090

Abstract

Several mixed oxides composed of Fe₃O₄, ZrO₂, and Al₂O₃ with different molar ratios were synthesized through a direct and simple mechanochemical approach. Subsequently, their physicochemical properties were investigated using a wide range of techniques, [...] Read more.

Several mixed oxides composed of Fe₃O₄, ZrO₂, and Al₂O₃ with different molar ratios were synthesized through a direct and simple mechanochemical approach. Subsequently, their physicochemical properties were investigated using a wide range of techniques, including TEM (transmission electron microscopy), XPS (X-ray photoelectron spectroscopy), XRD (X-ray diffraction), and N₂ adsorption/desorption, among others. These materials showed high surface areas and increased acidity compared to their respective counterparts. The catalytic activity of the synthesized materials was evaluated in the conversion of methyl levulinate (MEL) to γ-valerolactone (GVL) under microwave irradiation conditions, employing different alcohols as H-donor solvents (ethanol, 2-propanol, and 2-butanol). Due to their improved physicochemical properties originating from the ball-milling method, the as-synthesized materials (ZrFeOx 1:1, AlZrFeOx (5), and AlZrFeOx (10)) exhibited conversion rates of up to 99%, with complete selectivity for GVL after a relatively short reaction time of 30 min. Full article

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

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35 pages, 4170 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Advances in Methanol Steam Reforming Catalysts for Hydrogen Production

by Mengyuan Zhang, Diru Liu, Yiying Wang, Lin Zhao, Guangyan Xu, Yunbo Yu and Hong He

Catalysts 2025, 15(1), 36; https://doi.org/10.3390/catal15010036 - 3 Jan 2025

Cited by 6 | Viewed by 2962

Abstract

The pursuit of carbon neutrality has accelerated advancements in sustainable hydrogen production and storage methods, increasing the importance of methanol steam reforming (MSR) technology. Catalysts are central to MSR technology and are primarily classified into copper-based and noble metal-based catalysts. This review begins [...] Read more.

The pursuit of carbon neutrality has accelerated advancements in sustainable hydrogen production and storage methods, increasing the importance of methanol steam reforming (MSR) technology. Catalysts are central to MSR technology and are primarily classified into copper-based and noble metal-based catalysts. This review begins with an examination of the active components of these catalysts, tracing the evolution of the understanding of active sites over the past four decades. It then explores the roles of various supports and promoters, along with mechanisms of catalyst deactivation. To address the diverse perspectives on the MSR reaction mechanism, the existing research is systematically organized and synthesized, providing a detailed account of the reaction mechanisms associated with both catalyst types. The discussion concludes with a forward-looking perspective on MSR catalyst development, emphasizing strategies such as anti-sintering methods for copper-based catalysts, approaches to reduce byproduct formation in palladium-based catalysts, comprehensive research methodologies for MSR mechanisms, and efforts to enhance atomic utilization efficiency. Full article

(This article belongs to the Special Issue Catalytic Reforming and Hydrogen Production: From the Past to the Future)

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25 pages, 1711 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Bimetallic and Trimetallic Catalysts Advancements in the Conventional and MW-Assisted Propane Dehydrogenation Process

by Olga Muccioli, Concetta Ruocco and Vincenzo Palma

Catalysts 2024, 14(12), 950; https://doi.org/10.3390/catal14120950 - 22 Dec 2024

Cited by 2 | Viewed by 1792

Abstract

A huge variety of chemical commodities are built from propylene molecules, and its conventional production technologies (naphtha steam cracking and fluid catalytic cracking) are unable to satisfy C₃H₆’s increasing requirements. In this scenario, Direct Propane Dehydrogenation (PDH) provides a [...] Read more.

A huge variety of chemical commodities are built from propylene molecules, and its conventional production technologies (naphtha steam cracking and fluid catalytic cracking) are unable to satisfy C₃H₆’s increasing requirements. In this scenario, Direct Propane Dehydrogenation (PDH) provides a practical and reliable route for supplying this short demand due to the economic availability of the raw material (C₃H₈) and the high propylene selectivities. The main challenges of propane dehydrogenation technology are related to the design of very active catalysts with negligible byproduct formation. In particular, the issue of catalyst deactivation by coke deposition still requires further development. In addition, PDH is a considerable endothermic reaction, and the efficiency of this technology is strictly related to heat transfer management. Thus, this current review specifically discusses the recent advances in highly dispersed bimetallic and trimetallic catalysts proposed for the PDH reaction in both conventional-heated and microwave-heated reactors. From the point of view of catalyst development, the recent research is mainly addressed to obtain nanometric and single-atom catalysts and core–shell alloys: atomically dispersed metal atoms promote the desorption of surface-bonded propylene and inhibit its further dehydrogenation. The discussion is focused on the alternative formulations proposed in the last few years, employing active species and supports different from the classical Pt-Sn/Al₂O₃ catalyst. Concerning the conventional route of energy-supply to the catalytic bed, the advantage of using a membrane as well as fluidized bed reactors is highlighted. Recent developments in alternative microwave-assisted dehydrogenation (PDH) employing innovative catalytic systems based on silicon carbide (SiC) facilitate selective heating of the catalyst. This advancement leads to improved catalytic activity and propylene selectivity while effectively reducing coke formation. Additionally, it promotes environmental sustainability in the ongoing electrification of chemical processes. Full article

(This article belongs to the Special Issue Current Status and Future Aspects of Bimetallic and Trimetallic Catalysts)

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31 pages, 4435 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Carbon Materials Application in Heterogeneous Catalysis for Water Treatment: A Pathway to Process Intensification

by Ana Sofia G. G. Santos, Carla A. Orge, Manuel Fernando R. Pereira and Olívia Salomé G. P. Soares

Catalysts 2024, 14(12), 947; https://doi.org/10.3390/catal14120947 - 21 Dec 2024

Viewed by 1386

Abstract

Over the past few years, heterogeneous catalysis has been recognized as a versatile and efficient approach for applications in environmental remediation systems. The water treatment field is one of the most prominent beneficiaries of these various catalytic processes due to the crucial need [...] Read more.

Over the past few years, heterogeneous catalysis has been recognized as a versatile and efficient approach for applications in environmental remediation systems. The water treatment field is one of the most prominent beneficiaries of these various catalytic processes due to the crucial need to promote water reuse. However, there are still shortcomings related to the efficiency of these processes when applied to increasingly complex water matrices composed of different classes of contaminants. The present review aims to address the advantages associated with the application of catalytic processes and the diverse catalysts for water treatment while exploring how to take advantage of process integration as a solution to address the challenges posed by the growing complexity of environmental matrices. Full article

(This article belongs to the Special Issue Featured Papers in “Environmental Catalysis” Section)

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56 pages, 24168 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Synthesis, Characteristics, and Application of Hierarchical Porous Materials in Carbon Dioxide Reduction Reactions

by Ze-Long Guan, Yi-Da Wang, Zhao Wang, Ying Hong, Shu-Lin Liu, Hao-Wen Luo, Xian-Lin Liu and Bao-Lian Su

Catalysts 2024, 14(12), 936; https://doi.org/10.3390/catal14120936 - 18 Dec 2024

Cited by 2 | Viewed by 2581

Abstract

The reduction of carbon dioxide to valuable chemical products could favor the establishment of a sustainable carbon cycle, which has attracted much attention in recent years. Developing efficient catalysts plays a vital role in the carbon dioxide reduction reaction (CO₂RR) process, [...] Read more.

The reduction of carbon dioxide to valuable chemical products could favor the establishment of a sustainable carbon cycle, which has attracted much attention in recent years. Developing efficient catalysts plays a vital role in the carbon dioxide reduction reaction (CO₂RR) process, but with great challenges in achieving a uniform distribution of catalytic active sites and rapid mass transfer properties. Hierarchical porous materials with a porous hierarchy show great promise for application in CO₂RRs owing to the high specific surface area and superior porous connection. Plenty of breakthroughs in recent CO₂RR studies have been recently achieved regarding hierarchical porous materials, indicating that a summary of hierarchical porous materials for carbon dioxide reduction reactions is highly desired and significant. In this paper, we summarize the recent breakthroughs of hierarchical porous materials in CO₂RRs, including classical synthesis methods, advanced characterization technologies, and novel CO₂RR strategies. Moreover, by highlighting several significant works, the advantages of hierarchical porous materials for CO₂RRs are analyzed and revealed. Additionally, a perspective on hierarchical porous materials for CO₂RRs (e.g., challenges, potential catalysts, promising strategies, etc.) for future study is also presented. It can be anticipated that this comprehensive review will provide valuable insights for further developing efficient alternative hierarchical porous catalysts for CO₂ reduction reactions. Full article

(This article belongs to the Special Issue Research Advances in Zeolites and Zeolite-Based Catalysts)

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15 pages, 4408 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Cu/MOF-808 Catalyst for Transfer Hydrogenation of 5-Hydroxymethylfurfural to 2, 5-Furandimethanol with Formic Acid Mediation

by Jingxin Tan, Mengqi Li, Lingtao Liu, Lijian Wang, Haocun Wang, Junjie Bian and Chunhu Li

Catalysts 2024, 14(12), 929; https://doi.org/10.3390/catal14120929 - 17 Dec 2024

Viewed by 1405

Abstract

Biomass platform compound 5-Hydroxymethylfurfural (HMF), with its low price and abundant source, can be used as a renewable resource to replace traditional petrochemicals. MOF-808(Zr) has tunable active sites and excellent stability under high temperatures and acidic as well as basic environments, and the [...] Read more.

Biomass platform compound 5-Hydroxymethylfurfural (HMF), with its low price and abundant source, can be used as a renewable resource to replace traditional petrochemicals. MOF-808(Zr) has tunable active sites and excellent stability under high temperatures and acidic as well as basic environments, and the unsaturated coordination of metal ions within its framework structure can exhibit Lewis acidity, facilitating catalytic transfer hydrogenation from HMF to 2, 5-Furandimethanol (BHMF). The hydrothermal–impregnation–reduction method was used to prepare Cu/MOF-808 catalysts with high catalytic performance. Formic acid was chosen as the hydrogen donor solvent. The selectivity and yield of BHMF were 75.65% and 71%, respectively, at 150 °C for 4 h. A reaction pathway for the catalytic hydrogen transfer of HMF to BHMF was proposed. The high activity and stability of the Cu/MOF-808 catalyst with dual active sites provide a viable method for feasible hydrogenation of HMF to high value-added compounds. Full article

(This article belongs to the Special Issue Zeolites as Catalysts: Applications in Chemical Engineering, Energy Sources and Environmental Protection, 2nd Edition)

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31 pages, 10015 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Enantiopure 1,2-Diphenylethylenediamine (DPEDA) Motif in the Development of Organocatalysts for Asymmetric Reactions: Advances in the Last 20 Years

by Shilashi Badasa Oljira, Martina De Angelis, Andrea Sorato, Giulia Mazzoccanti, Simone Manetto, Ilaria D’Acquarica and Alessia Ciogli

Catalysts 2024, 14(12), 915; https://doi.org/10.3390/catal14120915 - 12 Dec 2024

Viewed by 4671

Abstract

1,2-Diphenylethylenediamine (DPEDA) is a privileged chiral scaffold being used in the construction of a broad variety of organocatalysts and ligands for enantioselective organic reactions. This molecule gave a significant contribution in the synthesis of structurally different bi/multifunctional organocatalysts. DPEDA played an essential role [...] Read more.

1,2-Diphenylethylenediamine (DPEDA) is a privileged chiral scaffold being used in the construction of a broad variety of organocatalysts and ligands for enantioselective organic reactions. This molecule gave a significant contribution in the synthesis of structurally different bi/multifunctional organocatalysts. DPEDA played an essential role in the development of organocatalysts capable of yielding important information on the different reaction mechanisms, like enamine, iminium, hydrogen-bonding and anion-binding catalysis. The aim of the present review is to highlight and summarize the achievements reached in the last 20 years (2004–2024) in the chemistry of DPEDA-based organocatalysts for asymmetric synthesis. Full article

(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)

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15 pages, 4188 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Role of the Solvent and Ultrasound Irradiation in the Preparation of TiO₂ for the Photocatalytic Degradation of Sulfamethoxazole in Water

by Alessandro Di Michele, Paola Sassi, Riccardo Vivani, Alessandro Minguzzi, Laura Prati and Carlo Pirola

Catalysts 2024, 14(12), 910; https://doi.org/10.3390/catal14120910 - 11 Dec 2024

Viewed by 889

Abstract

The preparation of titania-based photocatalysts has been largely investigated in the literature. Nevertheless, the study of the influence of different solvents in the synthesis mixture requires further analysis. Addressing this issue, we explored the potential of heterogeneous photocatalysis with nano-sized titanium dioxide (TiO [...] Read more.

The preparation of titania-based photocatalysts has been largely investigated in the literature. Nevertheless, the study of the influence of different solvents in the synthesis mixture requires further analysis. Addressing this issue, we explored the potential of heterogeneous photocatalysis with nano-sized titanium dioxide (TiO₂) synthesized via the sol–gel method with and without ultrasound for the degradation of sulfamethoxazole (SMX) in water. Specifically, we engineered TiO₂ nanoparticles within the 20–30 nm range, in order to work in the same particle size range of Evonik P25. The synthesis was conducted in five distinct solvents, n-hexane, decane, isopropanol, ethanol, and 1-octanol, and it was evaluated with the presence and absence of ultrasound. Following synthesis, the powders were thoroughly characterized. When nonpolar solvents were used, the photocatalysts were characterized by the presence of both anatase and brookite phases, while with polar solvents, the only polymorph present was anatase. A different behavior was shown by 1-octanol, where the role of the solvent was so important that US did not affect the final sample features. The samples prepared in ethanol and isopropanol exhibited superior activity compared to those synthesized in other solvents in the SMX photodegradation (about 35% after 6 h), and the effect of US during preparation resulted positive for all solvents (an average increase of SMX photodegradation in the range of 5–10% for the different photocatalysts for each degradation time). Full article

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16 pages, 7075 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Synthesis of Bimetallic Pd/Pt Truncated Nanocubes and Their Catalytic Performance in Selective Hydrogenation of Acetophenone

by Jingjing Bai, Xinkai Yang, Jianyu Chen, Bin Yue, Xueying Chen and Heyong He

Catalysts 2024, 14(12), 900; https://doi.org/10.3390/catal14120900 - 8 Dec 2024

Viewed by 939

Abstract

A series of bimetallic Pd/Pt truncated nanocube catalysts with similar morphologies and particle sizes but different platinum contents were successfully synthesized using a colloidal method without using any capping agents. Their hydrogenation properties were systematically studied and compared with their monometallic Pd or [...] Read more.

A series of bimetallic Pd/Pt truncated nanocube catalysts with similar morphologies and particle sizes but different platinum contents were successfully synthesized using a colloidal method without using any capping agents. Their hydrogenation properties were systematically studied and compared with their monometallic Pd or Pt nanocrystal counterparts. The results of EDX-mapping and line scanning show that platinum was relatively uniformly distributed on the surface of the Pd/Pt bimetallic nanocrystals and was not selectively deposited at the corners of the nanocrystals. The results of the selective hydrogenation of acetophenone demonstrate that the hydrogenation rate and the carbonyl selectivity of bimetallic Pd/Pt truncated nanocube catalysts are generally much higher than those of their monometallic Pd or Pt nanocrystal counterparts. It was found that the electronic interaction between palladium and platinum in the bimetallic Pd/Pt truncated nanocube catalysts and the corresponding hydrogenation activity in the selective hydrogenation of acetophenone are closely related to the molar ratio between platinum and palladium and the thickness of the platinum layer in the bimetallic Pd/Pt truncated nanocube catalyst. With an increase in the Pt/Pd molar ratio in the bimetallic Pd/Pt truncated nanocube catalysts, the activity and carbonyl selectivity in the acetophenone hydrogenation reaction increase first, reach a maximum when the molar ratio of Pt/Pd is 0.02 and the theoretical thickness of Pt is 1.3 atomic layers, and then decrease with a further increase in the Pt/Pd ratio. The hydrogenation rate of acetophenone on the Pd/Pt_0.02 catalyst reaches 1.07 × 10³ mmol·h⁻¹·g_cat.⁻¹, which is 79 and 75 times larger than that of the monometallic Pd and Pt nanocrystal catalysts, respectively. The maximum yield of the target product 1-phenylethanol on the Pd/Pt_0.02 truncated nanocube catalyst reaches 97.2%, which is 6.6% and 16.7% higher than that of the monometallic Pd and Pt nanocrystal catalysts, respectively. Full article

(This article belongs to the Special Issue Design and Synthesis of Nanostructured Catalysts, 2nd Edition)

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21 pages, 2890 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Visible-Light-Activated TiO₂-Based Photocatalysts for the Inactivation of Pathogenic Bacteria

by Farhana Haque, Allison Blanchard, Baileigh Laipply and Xiuli Dong

Catalysts 2024, 14(12), 855; https://doi.org/10.3390/catal14120855 - 25 Nov 2024

Cited by 3 | Viewed by 2387

Abstract

Pathogenic bacteria in the environment pose a significant threat to public health. Titanium dioxide (TiO₂)-based photocatalysts have emerged as a promising solution due to their potent antimicrobial effects under visible light and their generally eco-friendly properties. This review focuses on the [...] Read more.

Pathogenic bacteria in the environment pose a significant threat to public health. Titanium dioxide (TiO₂)-based photocatalysts have emerged as a promising solution due to their potent antimicrobial effects under visible light and their generally eco-friendly properties. This review focuses on the antibacterial properties of visible-light-activated, TiO₂-based photocatalysts against pathogenic bacteria and explores the factors influencing their efficacy. Various TiO₂ modification strategies are discussed, including doping with non-metals, creating structure defects, combining narrow-banded semiconductors, etc., to extend the light absorption spectrum from the UV to the visible light region. The factors affecting bacterial inactivation, and the underlying mechanisms are elucidated. Although certain modified TiO₂ nanoparticles (NPs) show antibacterial activities in the dark, they exhibit much higher antibacterial efficacies under visible light, especially with higher light intensity. Doping TiO₂ with elements such as N, S, Ce, Bi, etc., or introducing surface defects in TiO₂ NPs without doping, can effectively inactivate various pathogenic bacteria, including multidrug-resistant bacteria, under visible light. These surface modifications are advantageous in their simplicity and cost-effectiveness in synthesis. Additionally, TiO₂ can be coupled with narrow-banded semiconductors, resulting in narrower band gaps and enhanced photocatalytic efficiency and antibacterial activities under visible light. This information aids in understanding the current technologies for developing visible-light-driven, TiO₂-based photocatalysts and their application in inactivating pathogenic bacteria in the environment. Full article

(This article belongs to the Special Issue Photocatalysis towards a Sustainable Future)

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15 pages, 1855 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Mechanistic and Kinetic Analysis of Complete Methane Oxidation on a Practical PtPd/Al₂O₃ Catalyst

by Min Wang, Hai-Ying Chen, Yuliana Lugo-Jose, Joseph M. Fedeyko, Todd J. Toops and Jacqueline Fidler

Catalysts 2024, 14(12), 847; https://doi.org/10.3390/catal14120847 - 23 Nov 2024

Cited by 1 | Viewed by 1411

Abstract

A PtPd/Al₂O₃ catalyst developed for the complete oxidation of methane from the ventilation air of underground coal mines is compared against a model PdO/Al₂O₃ catalyst. Although the PtPd/Al₂O₃ catalyst is substantially more active and [...] Read more.

A PtPd/Al₂O₃ catalyst developed for the complete oxidation of methane from the ventilation air of underground coal mines is compared against a model PdO/Al₂O₃ catalyst. Although the PtPd/Al₂O₃ catalyst is substantially more active and stable than the model catalyst, the nature of active sites between the two catalysts is deemed to be fundamentally the same based on their response to different feed gas compositions and the evolution of surface CO adsorption complexes during time-resolved CO adsorption DRIFTS experiment. For both catalysts, coordinatively unsaturated Pd sites are considered the active centers for methane activation and the subsequent oxidation reaction. H₂O competes with CH₄ for the same active sites, resulting in severe inhibition. Additionally, the CH₄ oxidation reaction also causes self-inhibition. Taking both inhibition effects into consideration, a relatively simple kinetic model is developed. The model provides a good fit of the 72 sets of kinetic data collected on the PtPd/Al₂O₃ catalyst under practically relevant reaction conditions with CH₄ concentration in the range of 0.05–0.4%, H₂O concentration of 1.0–5.0%, and reaction temperatures of 450–700 °C. Kinetic parameters based on the model suggest that the CH₄ activation energy on the PtPd/Al₂O₃ catalyst is 96.7 kJ/mol, and the H₂O adsorption energy is −31.0 kJ/mol. Both values are consistent with the parameters reported in the literature. The model can be used to develop catalyst sizing guidelines and be incorporated into the control algorithm of the catalytic system. Full article

(This article belongs to the Special Issue Catalysts for Water and Air Pollution Control: Present and Future, 2nd Edition)

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14 pages, 4037 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Hydrogen and Oxygen Evolution on Flexible Catalysts Based on Nickel–Iron Coatings

by Dmytro Shyshkin, Loreta Tamašauskaitė-Tamašiūnaitė, Dijana Šimkūnaitė, Aldona Balčiūnaitė, Zita Sukackienė, Jūratė Vaičiūnienė, Birutė Šimkūnaitė-Stanynienė, Antanas Nacys and Eugenijus Norkus

Catalysts 2024, 14(12), 843; https://doi.org/10.3390/catal14120843 - 22 Nov 2024

Cited by 1 | Viewed by 1206

Abstract

The electrolysis of water is one of low-cost green hydrogen production technologies. The main challenge regarding this technology is designing and developing low-cost and high-activity catalysts. Herein, we present a strategy to fabricate flexible electrocatalysts based on nickel–iron (NiFe) alloy coatings. NiFe coatings [...] Read more.

The electrolysis of water is one of low-cost green hydrogen production technologies. The main challenge regarding this technology is designing and developing low-cost and high-activity catalysts. Herein, we present a strategy to fabricate flexible electrocatalysts based on nickel–iron (NiFe) alloy coatings. NiFe coatings were plated on the flexible copper-coated polyimide surface (Cu/PI) using the low-cost and straightforward electroless metal-plating method, with morpholine borane as a reducing agent. It was found that Ni₉₀Fe₁₀, Ni₈₀Fe₂₀, Ni₆₀Fe₄₀, and Ni₃₀Fe₇₀ coatings were deposited on the Cu/PI surface; then, the concentration of Fe²⁺ in the plating solution was 0.5, 1, 5, and 10 mM, respectively. The morphology, structure, and composition of Ni_xFe_y/Cu/PI catalysts have been examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and inductively coupled plasma–optical emission spectroscopy (ICP-OES), whereas their activity has been investigated for hydrogen evolution (HER) and oxygen evolution (OER) reactions in 1 M KOH using linear sweep voltammetry (LSVs). It was found that the Ni₈₀Fe₂₀/Cu/PI catalyst exhibited the lowest overpotential value of −202.7 mV for the HER, obtaining a current density of 10 mA cm⁻² compared to Ni₉₀Fe₁₀/Cu/PI (−211.9 mV), Ni₆₀Fe₄₀/Cu/PI (−276.3 mV), Ni₃₀Fe₇₀/Cu/PI (−278.4 mV), and Ni (−303.4 mV). On the other hand, the lowest OER overpotential (344.7 mV) was observed for the Ni₆₀Fe₄₀/Cu/PI catalyst, obtaining a current density of 10 mA cm⁻² compared to the Ni₃₅Fe₆₅ (369.9 mV), Ni₈₀Fe₂₀ (450.2 mV), and Ni₉₀Fe₁₀ (454.2 mV) coatings, and Ni (532.1 mV). The developed Ni₆₀Fe₄₀/Cu/PI catalyst exhibit a cell potential of 1.85 V at 10 mA cm⁻². The obtained catalysts seem to be suitable flexible catalysts for HER and OER in alkaline media. Full article

(This article belongs to the Section Catalytic Materials)

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18 pages, 4983 KiB

Open AccessEditor’s ChoiceArticle

Understanding the Negative Apparent Activation Energy for Cu₂O and CoO Oxidation Kinetics at High Temperature near Equilibrium

by Yang Wang, Haiyang Liu, Qiwei Duan and Zhenshan Li

Catalysts 2024, 14(11), 832; https://doi.org/10.3390/catal14110832 - 19 Nov 2024

Viewed by 1595

Abstract

The pairs of Cu₂O/CuO and CoO/Co₃O₄ as the carriers of transferring oxygen and storing heat are essential for the recently emerged high-temperature thermochemical energy storage (TCES) system. Reported research results of Cu₂O and CoO oxidation kinetics [...] Read more.

The pairs of Cu₂O/CuO and CoO/Co₃O₄ as the carriers of transferring oxygen and storing heat are essential for the recently emerged high-temperature thermochemical energy storage (TCES) system. Reported research results of Cu₂O and CoO oxidation kinetics show that the reaction rate near equilibrium decreases with the temperature, which leads to the negative activation energy obtained using the Arrhenius equation and apparent kinetics models. This study develops a first-principle-based theoretical model to analyze the Cu₂O and CoO oxidation kinetics. In this model, the density functional theory (DFT) is adopted to determine the reaction pathways and to obtain the energy barriers of elementary reactions; then, the DFT results are introduced into the transition state theory (TST) to calculate the reaction rate constants; finally, a rate equation is developed to describe both the surface elemental reactions and the lattice oxygen concentration in a grain. The reaction mechanism obtained from DFT and kinetic rate constants obtained from TST are directly implemented into the rate equation to predict the oxidation kinetics of Cu₂O without fitting experimental data. The accuracy of the developed theory is validated by experimental data obtained from the thermogravimetric analyzer (TGA). Comparing the developed theory with the traditional apparent models, the reasons why the latter cannot appropriately predict the true oxidation characteristics are explained. The reaction rate is jointly controlled by thermodynamics (reaction driving force) and kinetics (reaction rate constant). Without considering the effect of the reaction driving force, the negative apparent activation energy of Cu₂O oxidation is obtained. However, for CoO oxidation, the negative apparent activation energy is still obtained although the effect of the reaction driving force is considered. According to the DFT results, the activation energy of the overall CoO oxidation reaction is negative, but the energy barriers of the elementary reactions are positive. Moreover, according to the first-principle-based rate equation theory, the pre-exponential factor in the kinetic model is dependent on the partition function ratio and decreases with the temperature for the Cu₂O and CoO oxidation near equilibrium, which results in the apparent activation energy being slightly lower than the actual value. Full article

(This article belongs to the Section Computational Catalysis)

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19 pages, 3816 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Optimizing Fe-N-C Electrocatalysts for PEMFCs: Influence of Constituents and Pyrolysis on Properties and Performance

by Ilias Maniatis, Georgios Charalampopoulos, Fotios Paloukis and Maria K. Daletou

Catalysts 2024, 14(11), 780; https://doi.org/10.3390/catal14110780 - 4 Nov 2024

Cited by 5 | Viewed by 1741

Abstract

Proton exchange membrane fuel cells (PEMFCs) are promising alternative technologies with applications in stationary power systems, vehicles, and portable electronics due to their low temperature operation, fast start-up, and environmental advantages. However, the high cost of platinum-based catalysts, in particular for the oxygen [...] Read more.

Proton exchange membrane fuel cells (PEMFCs) are promising alternative technologies with applications in stationary power systems, vehicles, and portable electronics due to their low temperature operation, fast start-up, and environmental advantages. However, the high cost of platinum-based catalysts, in particular for the oxygen reduction reaction (ORR) of the cathode side, prevents their widespread incorporation. Fe-N-C electrocatalysts have emerged as viable alternatives to platinum. In this study, different precursor components were investigated for the way that they affect the pyrolysis process, which is crucial for tailoring the final catalyst properties. In particular, carbon allotropes such as carbon Vulcan, Ketjenblack, and carbon nanotubes were selected for their unique structures and properties. In addition, various sources of iron (FeCl₂, FeCl₃, and K[Fe(SCN)₄]) were evaluated. The influence of the pyrolysis atmosphere on the resulting Fe-N-C catalyst structures was also assessed. Through an integrated structure and surface chemistry analyses, as well as electrochemical tests with rotating disk electrode experiments in acidic media, the ORR performance and stability of these catalysts were defined. By examining the relationships between carbon sources and iron precursors, this research provides valuable information for the optimization of Fe-N-C catalysts in fuel cell applications. Full article

(This article belongs to the Special Issue Advanced Catalysis for Energy and Environmental Applications)

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