Catalysts

21 pages, 2481 KiB

Open AccessFeature PaperArticle

Unlocking Catalytic Efficiency: How Preparation Strategies and Copper Loading Enhance Hydroxyapatite Catalysts for NH₃ Oxidation

by Sebastiano Campisi, Melissa Greta Galloni and Antonella Gervasini

Catalysts 2025, 15(4), 405; https://doi.org/10.3390/catal15040405 - 21 Apr 2025

Abstract

The selective catalytic oxidation of ammonia (NH₃-SCO) is gaining attention due to the hazardous nature of NH₃ and its inclusion in emission reduction frameworks such as the National Emission Ceilings Directive and the Gothenburg Protocol (1999). Copper-based hydroxyapatite (Cu/HAP) catalysts [...] Read more.

The selective catalytic oxidation of ammonia (NH₃-SCO) is gaining attention due to the hazardous nature of NH₃ and its inclusion in emission reduction frameworks such as the National Emission Ceilings Directive and the Gothenburg Protocol (1999). Copper-based hydroxyapatite (Cu/HAP) catalysts have emerged as a promising solution, offering high activity and cost-effectiveness. This study evaluated two preparation methods: a one-pot co-precipitation technique and post-synthesis copper deposition, varying both the contact time and copper concentration. The influence of copper loading and preparation method on catalyst performance in NH₃-SCO was investigated in a continuous flow reactor over a temperature range of 200–500 °C, with a fixed gas hourly space velocity (GHSV) of 120,000 h⁻¹ and an NH₃/O₂ ratio of 0.03. X-ray diffraction and DR-UV spectroscopy confirmed the high crystallinity of HAP and provided insights into copper speciation. X-ray photoelectron spectroscopy revealed that Cu/HAP catalysts prepared via one-pot co-precipitation predominantly contained isolated Cu²⁺ species, which were associated with high catalytic activity in selective NH₃-SCO. Conversely, a higher degree of copper structuring was observed in catalysts prepared by post-synthesis deposition, particularly at higher Cu loadings. These findings highlight the potential to tailor Cu structuring on HAP to enhance performance in NH₃-SCO through optimized preparation strategies. Full article

(This article belongs to the Special Issue New Trends in Catalysis: ELITECAT 2024)

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12 pages, 2819 KiB

Open AccessArticle

Hydrogenation of Dodecanoic Acid over Iridium-Based Catalysts

by Heny Puspita Dewi and Shun Nishimura

Catalysts 2025, 15(4), 404; https://doi.org/10.3390/catal15040404 - 21 Apr 2025

Abstract

This study develops iridium (Ir)-based catalysts for the hydrogenation of dodecanoic acid, a medium-chain fatty acid abundant in palm kernel and coconut oils, for producing fatty alcohols and alkanes. Among various supports such as AlOOH, SiO₂, TiO₂, Nb₂ [...] Read more.

This study develops iridium (Ir)-based catalysts for the hydrogenation of dodecanoic acid, a medium-chain fatty acid abundant in palm kernel and coconut oils, for producing fatty alcohols and alkanes. Among various supports such as AlOOH, SiO₂, TiO₂, Nb₂O₅, MoO₃, Ta₂O₅, ZrO₂, and WO₃ for 7.5 wt% Ir loading, an Ir-impregnated Nb₂O₅ (Ir/Nb₂O₅) catalyst demonstrated remarkable performance with 100% conversion and a high dodecanol yield (89.1%) under mild conditions (170 °C, 4.0 MPa H₂), while at higher temperatures and pressures (200 °C, 8.0 MPa H₂), Ir-impregnated MoO₃ (Ir/MoO₃) produced dodecane as the main product with a yield of 90.7%. These findings can tailor product selectivity toward desired bio-based chemicals and fuels, offering sustainable pathways for fatty acid hydrogenation by optimizing catalyst supports and reaction conditions in the Ir-based catalyst. Full article

(This article belongs to the Special Issue Biomass Catalytic Conversion to Value-Added Chemicals)

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20 pages, 10507 KiB

Open AccessArticle

Preparation of Oxygen Reduction Catalyst Electrodes by an Efficient Electrodeposition Method on HNO₃-Activated Carbon Paper

by Yongjian Guo, Liheng Zhou, Wenwen Zhang and Qi Zhang

Catalysts 2025, 15(4), 403; https://doi.org/10.3390/catal15040403 - 21 Apr 2025

Abstract

The proton exchange membrane fuel cell (PEMFC) is a promising energy conversion technology. The synthesis route of the cathode oxygen reduction catalyst electrode is an important factor affecting the development of the battery. In traditional technology, Pt shows low utilization of oxygen reduction [...] Read more.

The proton exchange membrane fuel cell (PEMFC) is a promising energy conversion technology. The synthesis route of the cathode oxygen reduction catalyst electrode is an important factor affecting the development of the battery. In traditional technology, Pt shows low utilization of oxygen reduction activity due to poor contact between catalyst nanoparticles (NP), the electrolyte, and oxygen. In this work, an effective electrochemical method for the preparation of a Pt/C catalyst electrode was proposed. The carbon paper (CP) substrate was electrochemically activated by HNO₃, and then, Pt nanoparticles were prepared on CP by one-step electrodeposition. Secondly, a Density Functional Theory (DFT) investigation was carried out to elucidate that the N-doped catalyst facilitates the desorption of intermediates from the catalyst surface and promotes the oxygen reduction reaction. Thirdly, the effects of acid activation voltage were discussed. The result shows that increasing the voltage significantly increases the concentration of C–N groups and decreases the particle size of Pt. The effects of acidification concentration were investigated at an optimal activation voltage of 1.6 V. When the activation concentration was 0.1 mol, Pt⁰ reached an optimal value, and therefore obtained an equilibrium between the adsorption of oxygen on Pt and the desorption of the intermediates. Pt/0.1CP_1.6 exhibits better performance than commercial catalysts in oxygen reduction reactions. After 5000 testing cycles, the catalyst showed a constant durability with only a 3.0 mV·dec⁻¹ increase of the Tafel slope and just a 6.7 m²·g_Pt⁻¹ decline of the ECSA. Full article

(This article belongs to the Section Industrial Catalysis)

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17 pages, 13979 KiB

Open AccessArticle

Waste Incineration Fly Ash-Based Bifunctional Catalyst for Upgrading Glucose to Levulinic Acid

by Rui Zhang, Han Wu, Jiantao Li, Dezhi Chen, Shimin Li, Jiale Chen, Xiaoyun Li, Jian Xiong, Zhihao Yu and Xuebin Lu

Catalysts 2025, 15(4), 402; https://doi.org/10.3390/catal15040402 - 19 Apr 2025

Viewed by 111

Abstract

The safe and resource-efficient utilization of waste incineration fly ash (WIFA) has emerged as a pressing challenge in solid waste management. In this work, WIFA was used to prepare a bifunctional catalyst (Metals_x/4@WIFA-S) for the production of levulinic acid (LA) from [...] Read more.

The safe and resource-efficient utilization of waste incineration fly ash (WIFA) has emerged as a pressing challenge in solid waste management. In this work, WIFA was used to prepare a bifunctional catalyst (Metals_x/4@WIFA-S) for the production of levulinic acid (LA) from glucose. The yield of LA was 42.3% with water as the solvent. Moreover, adding 20% γ-valerolactone (GVL) to the system increased the yield to 50.7%. Reaction kinetics and molecular dynamics simulations were applied to elucidate the mechanism by which the solvent system enhanced the catalytic performance of the Metals_x/4@WIFA-S catalyst. Additionally, the environmental risks of WIFA in the preparation of catalysts were evaluated. The dioxin decomposition rate in the catalyst was calculated to be 99.87%, effectively achieving the detoxification of the catalyst. The concentration of heavy metals in the hydrolysate complied with emission standards, thereby reducing environmental risk. This study confirms that waste incineration fly ash-based bifunctional catalysts are effective and safe catalysts with great potential for application in biomass catalysis. Full article

(This article belongs to the Section Biomass Catalysis)

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75 pages, 20332 KiB

Open AccessFeature PaperReview

A Review on the Research Progress of Zeolite Catalysts for Heavy Oil Cracking

by Lisha Wei, Hui Wang, Qi Dong, Yongwang Li and Hongwei Xiang

Catalysts 2025, 15(4), 401; https://doi.org/10.3390/catal15040401 - 19 Apr 2025

Viewed by 57

Abstract

The efficient utilization of heavy oil is of great significance to alleviating the global energy crisis. How to efficiently convert heavy oil into high-value-added light fuel oil has become a hot issue in the field of petrochemicals. As the residual part of crude [...] Read more.

The efficient utilization of heavy oil is of great significance to alleviating the global energy crisis. How to efficiently convert heavy oil into high-value-added light fuel oil has become a hot issue in the field of petrochemicals. As the residual part of crude oil processing, heavy oil has a complex composition and contains polycyclic aromatic hydrocarbons, long-chain alkanes, and heteroatom compounds, which makes it difficult to process directly. Zeolite, as an important type of solid acid catalyst, has a unique pore structure, adjustable acidity, and good thermal stability. It can promote the efficient cracking and conversion of heavy oil molecules, reduce coke formation, and improve the yield and quality of light oil products. This paper systematically reviews the development status of heavy oil cracking technology, focusing on the structural characteristics, acidity regulation of zeolite catalysts, and their applications in heavy oil cracking and hydrocracking. The mechanism of the cracking reaction of polycyclic aromatic hydrocarbons and long-chain alkanes is analyzed in detail, and the catalytic characteristics and modification methods of zeolite in the reaction process are explained. In addition, this paper summarizes the main challenges faced by zeolite catalysts in practical applications, including uneven acidity distribution, limited pore diffusion, and easy catalyst deactivation, and proposes targeted development strategies. Finally, this paper looks forward to the future development direction of zeolite catalysts in the field of heavy oil cracking and upgrading reactions, emphasizes the importance of structural optimization and multi-scale characterization, and provides theoretical support and practical reference for the design and industrial application of efficient zeolite catalysts. Full article

(This article belongs to the Section Catalytic Materials)

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19 pages, 3763 KiB

Open AccessFeature PaperArticle

Synthesis of Nitrogen-Doped Biomass-Based Activated-Carbon-Supported Nickel Nanoparticles for Hydrazine Oxidation

by Virginija Ulevičienė, Aldona Balčiūnaitė, Daina Upskuvienė, Ance Plavniece, Aleksandrs Volperts, Galina Dobele, Aivars Zhurinsh, Gediminas Niaura, Loreta Tamašauskaitė-Tamašiūnaitė and Eugenijus Norkus

Catalysts 2025, 15(4), 400; https://doi.org/10.3390/catal15040400 - 19 Apr 2025

Viewed by 139

Abstract

In this study we present an application of wood biomass—alder wood char—as the carbon precursor for the synthesis of novel and sustainable nitrogen-doped activated-carbon-supported nickel nanoparticle catalyst (AWC-Ni-N) for hydrazine oxidation. For comparison, the wood-based carbon material doped with nitrogen only (AWC-N) was [...] Read more.

In this study we present an application of wood biomass—alder wood char—as the carbon precursor for the synthesis of novel and sustainable nitrogen-doped activated-carbon-supported nickel nanoparticle catalyst (AWC-Ni-N) for hydrazine oxidation. For comparison, the wood-based carbon material doped with nitrogen only (AWC-N) was also synthesized. Extensive characterization, including SEM, Raman spectroscopy, XPS, and XRD revealed the catalysts’ microstructure and properties. Electrochemical testing demonstrated that the AWC-Ni-N catalyst significantly enhanced the efficiency of the hydrazine oxidation reaction. In addition, direct N₂H₄-H₂O₂ single-fuel-cell tests were conducted using the prepared AWC-N and AWC-Ni-N catalysts as the anodes and cathodes. Peak power densities of up to 10.8 mW cm⁻² were achieved at 25 °C, corresponding to a current density of 27 mA cm⁻² and a cell voltage of 0.4 V when the AWC-Ni-N catalyst was used as both the anode and cathode. Furthermore, the peak power density increased by approximately 1.6 and 2.9 times, respectively, when the operating temperature was raised from 25 °C to 55 °C for the AWC-N and AWC-Ni-N catalysts. Overall, the AWC-N and AWC-Ni-N catalysts demonstrated significant potential as anode and cathode materials in direct N₂H₄-H₂O₂ fuel cells. Full article

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

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20 pages, 17600 KiB

Open AccessArticle

Effects of the Intrinsic Structures of Graphite Felt and Carbon Cloth on the Working Condition of Iron-Chromium Redox Flow Batteries

by Jun Tian, Chuanyu Sun, Bowen Qu, Huan Zhang, Shuqi Liu, Meiqi Fei and Shuang Yan

Catalysts 2025, 15(4), 399; https://doi.org/10.3390/catal15040399 - 19 Apr 2025

Viewed by 44

Abstract

The design parameters of large-scale iron-chromium redox flow batteries (ICRFB) encompass a wide range of internal and external operational conditions, including electrodes, membranes, flow rate, and temperature, among others. Among these factors, the intrinsic structures of graphite felt (GF) and carbon cloth (CC) [...] Read more.

The design parameters of large-scale iron-chromium redox flow batteries (ICRFB) encompass a wide range of internal and external operational conditions, including electrodes, membranes, flow rate, and temperature, among others. Among these factors, the intrinsic structures of graphite felt (GF) and carbon cloth (CC) play a pivotal role in determining the overall working conditions of ICRFBs. This study systematically investigates the multifaceted relationship between the intrinsic structure of the GF and CC and their impact on the operational performance of ICRFBs. The fundamental difference between the two types of electrodes lies in the intrinsic structure space available in them for electrolyte penetration. A systematic analysis of the structure–activity relation between the electrodes and the initial internal resistance, as well as the operating temperature of the cell, was performed. Additionally, the influence of the electrode structure on critical parameters, including the flow rate, membrane selection (Nafion 212 and Nafion 115), and performance of electrodeposition catalysts (bismuth and indium), is examined in detail. Under varying operating conditions, the intrinsic structures of GF and CC turn out to be a crucial factor, providing a robust basis for electrode selection and performance optimization in large-scale ICRFB systems. Full article

(This article belongs to the Section Catalytic Materials)

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16 pages, 3197 KiB

Open AccessArticle

Construction of Moiré-like Structure to Efficiently Enhance the H₂ Photogeneration

by Guanglu Yang, Meng Yuan, Yuexi Hao, Yizhe Wang, Haochen Jiao, Yudong Li, Desheng Zhou, Xing Liu, Haiyue Yang and Chengyu Wang

Catalysts 2025, 15(4), 398; https://doi.org/10.3390/catal15040398 - 19 Apr 2025

Viewed by 146

Abstract

Photocatalytic hydrogen production could sustainably and efficiently convert solar energy. However, a low light utilization ratio limits the wide application. Herein, a Moiré-like structure was constructed in the TiO₂ body to improve the light absorption by multiple reflections and suitable light dispersion [...] Read more.

Photocatalytic hydrogen production could sustainably and efficiently convert solar energy. However, a low light utilization ratio limits the wide application. Herein, a Moiré-like structure was constructed in the TiO₂ body to improve the light absorption by multiple reflections and suitable light dispersion and diffraction based on similar wavelength and nick. Furthermore, the Moiré-like structure slightly reduces the band gap and accelerates the separation of the photogenerated electrons and holes, and the mass transfer was enhanced by the regular nano-channels and Bernoulli phenomenon. After calcination at 500 °C (M-T500), compared with pure TiO₂, M-T500 achieved a 20% increase in RhB degradation efficiency and a double increase in hydrogen production rate, thus providing a novel design for catalysts and a high catalytic strategy. Moreover, the nearly 100% recovery rate supported environmental protection and sustainable development. Full article

(This article belongs to the Collection Photocatalytic Water Splitting)

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26 pages, 4247 KiB

Open AccessFeature PaperReview

Precious Metals Catalyze the Saturated Hydrogenation of Polycyclic Aromatic Hydrocarbons in Coal Tar

by Xiaoyu Qiao, Xinru Wang, Changrui Tan, Liang Ma, Bofeng Zhang, Jingpei Cao and Hongyan Wang

Catalysts 2025, 15(4), 397; https://doi.org/10.3390/catal15040397 - 19 Apr 2025

Viewed by 161

Abstract

As a significant by-product of coal pyrolysis processes, coal tar is rich in polycyclic aromatic hydrocarbons (PAHs), garnering considerable attention for their potential conversion into high-value products through saturation hydrogenation. This paper presents a comprehensive review of recent advancements in two key areas: [...] Read more.

As a significant by-product of coal pyrolysis processes, coal tar is rich in polycyclic aromatic hydrocarbons (PAHs), garnering considerable attention for their potential conversion into high-value products through saturation hydrogenation. This paper presents a comprehensive review of recent advancements in two key areas: progress in high-activity saturated hydrogenation of PAHs catalyzed by precious metals and the regulation of cis–trans isomeric configuration of their hydrogenation products. Furthermore, the investigation addresses two critical challenges involved in the field: the susceptibility of precious metal catalysts to sulfur poisoning during the coal tar’s hydrogenation and the difficulty in controlling the stereo-isomerization of hydrogenation products. This review will advance fundamental understanding of PAHs hydrogenation mechanisms and provide critical technical guidance in coal tar utilization, supporting the sustainable development of clean energy technologies and high-value chemical production from coal by-products. Full article

(This article belongs to the Special Issue Latest Advances and Prospects of Catalytic Dehydrogenation and Hydrogenation)

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20 pages, 8283 KiB

Open AccessReview

Heterogeneous Acid Catalysts for Biodiesel Production: Effect of Physicochemical Properties on Their Activity and Reusability

by Jingfeng Hua, Mimi Ji, Ping Jiao, Zhixian Yin, Qineng Xia, Lingchang Jiang, Jing Zhang and Hu Pan

Catalysts 2025, 15(4), 396; https://doi.org/10.3390/catal15040396 - 18 Apr 2025

Viewed by 197

Abstract

Replacing homogeneous acids with heterogeneous acids provides an appealing approach for biodiesel production due to their reusability and easy recycling. The physicochemical properties of heterogeneous acids have a significant influence on catalytic activity and reusability. Herein, the influence of physicochemical properties (i.e., acid [...] Read more.

Replacing homogeneous acids with heterogeneous acids provides an appealing approach for biodiesel production due to their reusability and easy recycling. The physicochemical properties of heterogeneous acids have a significant influence on catalytic activity and reusability. Herein, the influence of physicochemical properties (i.e., acid density, acid strength, acid type, wettability, thermal sensitivity, and magnetism) on catalytic activity and recyclability is elaborately discussed. Characterization techniques for identifying physicochemical properties are elaborated. Methods for regulating physicochemical properties are summarized. Finally, the opportunities and challenges of heterogeneous acid use for biodiesel production are discussed. This review provides theoretical guidance for developing efficient and stable heterogeneous acid catalysts for biodiesel production by adjusting their physicochemical properties. Full article

(This article belongs to the Special Issue Advances in Catalysis for Sustainable Energy and Environmental Remediation)

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28 pages, 6502 KiB

Open AccessReview

Recent Advances in Enantioselective Transition Metal Catalysis Mediated by Ligand–Substrate Noncovalent Interactions

by Zhen Cao, Dongyang He, Lin Luo and Wenjun Tang

Catalysts 2025, 15(4), 395; https://doi.org/10.3390/catal15040395 - 18 Apr 2025

Viewed by 71

Abstract

Enantioselective transition metal catalysis is undoubtedly a cornerstone at the frontier of chemistry, attracting intense interest from both academia and the pharmaceutical industry. Central to this field is the strategic utilization of noncovalent interactions (NCIs), including hydrogen bonding, ion pairing, and π-system engagements, [...] Read more.

Enantioselective transition metal catalysis is undoubtedly a cornerstone at the frontier of chemistry, attracting intense interest from both academia and the pharmaceutical industry. Central to this field is the strategic utilization of noncovalent interactions (NCIs), including hydrogen bonding, ion pairing, and π-system engagements, which not only drive asymmetric synthesis but also enable precise stereochemical control in transition metal-catalyzed transformations. Recent breakthroughs have unveiled a new generation of rationally designed ligands that exploit ligand–substrate noncovalent interactions, emerging as indispensable tools for stereocontrolled synthesis and setting new paradigms in ligand engineering. These advancements establish a transformative framework for ligand engineering, bridging fundamental mechanistic insights with practical synthetic utility. In this review, the judicious design concepts and syntheses of novel ligands from the past five years were highlighted and their synthetic applications in asymmetric catalysis were detailed. Full article

(This article belongs to the Special Issue Recent Catalysts for Organic Synthesis)

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20 pages, 3281 KiB

Open AccessArticle

Effective and High-Performance MgFe₂O₄/Mg-MOF Composite for Direct Methanol Fuel Cells

by M. R. Hussein, Amna A. Kotp, E. M. Elsayed, A. M. Elseman and Mohamed Sh. Abdel-wahab

Catalysts 2025, 15(4), 394; https://doi.org/10.3390/catal15040394 - 18 Apr 2025

Viewed by 207

Abstract

The development of efficient and sustainable electrocatalysts for optimizing methanol oxidation reactions (MORs) in direct methanol fuel cells (DMFCs) is crucial for the innovation of clean electrode energy technologies. This study highlights the synthesis and characterization of magnesium ferrite (MgFe₂O₄ [...] Read more.

The development of efficient and sustainable electrocatalysts for optimizing methanol oxidation reactions (MORs) in direct methanol fuel cells (DMFCs) is crucial for the innovation of clean electrode energy technologies. This study highlights the synthesis and characterization of magnesium ferrite (MgFe₂O₄) and magnesium-based metal–organic framework (Mg-MOF) composites, utilizing cost-effective and scalable methods such as co-precipitation and ultrasound-assisted synthesis. The composite material, prepared in a 1:1 ratio, demonstrated enhanced catalytic performance due to the synergistic integration of MgFe₂O₄ and Mg-MOF. Comprehensive structural and morphological analyses, including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), the Brunauer–Emmett–Teller (BET) technique, and X-ray photoelectron spectroscopy (XPS), confirmed the successful formation of the composite. Also, the modification of magnetic properties, particularly the values of coercive force (Hc), led to a significant enhancement in electrical and catalytic performance. The material exhibited mesoporous characteristics and an improved surface area. Electrochemical evaluations revealed superior MOR activity for the composite electrode, achieving a current density of 31.5 mA∙cm⁻² at 1 M methanol with an onset potential of 0.34 V versus Ag/AgCl, measured at a scan rate of 100 mV/s. Remarkably, the composite electrode showed a 75% improvement in current density compared to its components. Additionally, the composite exhibited a low overpotential of 350 mV and favorable Tafel slopes of 22.54 and 4.27 mV∙dec⁻¹ at high and low potentials, respectively, confirming rapid methanol oxidation kinetics on this electrode. It also demonstrated excellent stability, retaining 97.4% of its current density after 1 h. Electrochemical impedance spectroscopy (EIS) further revealed a reduced charge transfer resistance of 9.26 Ω, indicating enhanced conductivity and catalytic efficiency. These findings underscore the potential of MgFe₂O₄/Mg-MOF composites as cost-effective and high-performance anode materials for DMFCs, paving the way for sustainable energy solutions. Full article

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14 pages, 4222 KiB

Open AccessFeature PaperArticle

Squaramide-Catalyzed Three-Component Asymmetric [2 + 2 + 1] Cycloaddition Reaction Between 3-Hydroxy-1H-pyrrole-2,5-diones with Nitrosobenzene and Ethyl Diazoacetate

by Dong-Hua Xie, Yang Du and Da-Ming Du

Catalysts 2025, 15(4), 393; https://doi.org/10.3390/catal15040393 - 17 Apr 2025

Viewed by 133

Abstract

An asymmetric [2 + 2 + 1] cycloaddition reaction between three-component 3-hydroxy-1H-pyrrole-2,5-diones, ethyl diazoacetate, and nitrosobenzene was successfully developed. A new series of chiral polysubstituted chiral isoxazolidinopyrrolidinediones with three consecutive stereocentres were obtained in up to 87% yield with up to [...] Read more.

An asymmetric [2 + 2 + 1] cycloaddition reaction between three-component 3-hydroxy-1H-pyrrole-2,5-diones, ethyl diazoacetate, and nitrosobenzene was successfully developed. A new series of chiral polysubstituted chiral isoxazolidinopyrrolidinediones with three consecutive stereocentres were obtained in up to 87% yield with up to >20:1 dr and 78% ee. In addition, a scaled-up synthesis was carried out, and a possible reaction mechanism was also proposed. Full article

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

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21 pages, 6034 KiB

Open AccessArticle

Silver-Modified Biochar: Investigating NO₂ Adsorption and Reduction Efficiency at Different Temperatures

by Flavia Tavares, Fernanda F. Camilo, Mohamed Zbair, Lionel Limousy and Jocelyne Brendle

Catalysts 2025, 15(4), 392; https://doi.org/10.3390/catal15040392 - 17 Apr 2025

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Abstract

This study investigates the adsorption and reduction of NO₂ on biochar (BCC) and silver-modified biochar (Ag-BCC) in a continuous flow. Ag-BCC showed a higher NO₂ adsorption capacity (11.78 mg/g) than BCC (11.04 mg/g) at 200 °C, despite its lower surface area [...] Read more.

This study investigates the adsorption and reduction of NO₂ on biochar (BCC) and silver-modified biochar (Ag-BCC) in a continuous flow. Ag-BCC showed a higher NO₂ adsorption capacity (11.78 mg/g) than BCC (11.04 mg/g) at 200 °C, despite its lower surface area (345 vs. 402 m²/g). While neither material decomposed NO₂ at 22 °C, Ag-BCC achieved a NO/NO₂ ratio of 20% (vs. 9% for BCC) at 200 °C, highlighting the catalytic role of silver in NO₂ conversion. Breakthrough curve modeling identified the Dose–Response model as optimal, accurately describing adsorption kinetics at all temperatures (22–200 °C). Adsorption rate constants decreased with increasing temperature, confirming exothermicity. Overall, the results highlight the enhanced performance of Ag-BCC for NO₂ capture and conversion, underlining the potential of surface-modified biochars in the sustainable mitigation of air pollution. Full article

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

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32 pages, 16925 KiB

Open AccessReview

Recent Advances in Iron Oxide-Based Heterojunction Photo-Fenton Catalysts for the Elimination of Organic Pollutants

by Yiqian Wu, Cong Wang, Lan Wang and Chen Hou

Catalysts 2025, 15(4), 391; https://doi.org/10.3390/catal15040391 - 17 Apr 2025

Viewed by 109

Abstract

Organic pollutants released into water bodies have posed a serious threat to aquatic ecosystems. The elimination of organic pollutants from water through the photo-Fenton process has attracted extensive attention. Among various photo-Fenton catalysts, iron oxides have been intensively studied due to their environmentally [...] Read more.

Organic pollutants released into water bodies have posed a serious threat to aquatic ecosystems. The elimination of organic pollutants from water through the photo-Fenton process has attracted extensive attention. Among various photo-Fenton catalysts, iron oxides have been intensively studied due to their environmentally benign characteristics and abundance. However, the rapid recombination of photogenerated charge carriers (e⁻–h⁺) and slow Fe(III)/Fe(II) cycling of iron oxides restrict their catalytic performance. Thus, this state-of-the-art review focuses on the recent research development regarding iron oxide-based heterojunctions with enhanced catalytic performance to eliminate organic pollutants. This review provides a fundamental understanding of the iron-based heterogeneous photo-Fenton reaction. In addition, various heterojunctions for photocatalytic applications are comprehensively summarized. A thorough discussion is held on the material design for iron oxide-based heterojunctions with improved photo-Fenton catalytic performance. Ultimately, the challenges and prospects of iron oxide-based heterojunction catalysts for photo-Fenton water decontamination are outlined. Full article

(This article belongs to the Special Issue Recent Advances in Photocatalytic Wastewater Treatment)

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18 pages, 3977 KiB

Open AccessFeature PaperArticle

The Improved Cooperation of Metal–Acid Catalysis Using Encapsulation and P Doping Enhances the Preparation of 3-Acetyl-1-Propanol

by Zezheng Bing, Yuanyuan Gao, Zhongyi Liu and Qiaoyun Liu

Catalysts 2025, 15(4), 390; https://doi.org/10.3390/catal15040390 - 17 Apr 2025

Viewed by 114

Abstract

Biomass, as a renewable carbon resource, holds broad application prospects. Among various bio-based platform molecules, furan derivatives play a significant role in green chemical production. Notably, the conversion of 2-methylfuran (2-MF) to 3-acetyl-1-propanol (3-AP) over bifunctional catalysts has attracted considerable interest. In this [...] Read more.

Biomass, as a renewable carbon resource, holds broad application prospects. Among various bio-based platform molecules, furan derivatives play a significant role in green chemical production. Notably, the conversion of 2-methylfuran (2-MF) to 3-acetyl-1-propanol (3-AP) over bifunctional catalysts has attracted considerable interest. In this study, a Pd@PHZSM-5 catalyst was prepared by encapsulating Pd nanoparticles within P-doped HZSM-5 for 2-MF conversion. The encapsulation improved Pd dispersion and metal–acid synergy, enhancing both catalytic activity and 3-AP selectivity. Additionally, phosphorus doping increased HZSM-5 crystallinity, resulting in excellent stability. This work provides a feasible strategy for optimizing metal–acid cooperation, offering theoretical guidance for bifunctional catalysis and biomass valorization. Full article

(This article belongs to the Special Issue Industrial Applications of High-Value Added Biomass Conversion)

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10 pages, 4795 KiB

Open AccessArticle

Highly Efficient and Sustainable HT@NC/Pd Catalysts for Suzuki Coupling and Their Application in Elacestrant Synthesis

by Jiajun He, Muwei Liu, Chao Chen, Guozhang Li, Kai Zheng and Chao Shen

Catalysts 2025, 15(4), 389; https://doi.org/10.3390/catal15040389 - 17 Apr 2025

Viewed by 112

Abstract

Mg-Al hydrotalcite (HT), comprising Mg²⁺ and Al³⁺ as layered hydroxide cations, was synthesized via a hydrothermal process at 200 °C. The HT was evaluated as a carrier, and subsequently, palladium was immobilized on the surface of the hydrotalcite (HT/NC), resulting in [...] Read more.

Mg-Al hydrotalcite (HT), comprising Mg²⁺ and Al³⁺ as layered hydroxide cations, was synthesized via a hydrothermal process at 200 °C. The HT was evaluated as a carrier, and subsequently, palladium was immobilized on the surface of the hydrotalcite (HT/NC), resulting in the development of an innovative biomass-based palladium catalyst. The catalyst underwent analysis by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). It exhibited remarkable catalytic efficiency and superior activity as a catalyst in the Suzuki–Miyaura coupling reaction in water. The catalyst was recyclable without a decline in activity and could be utilized more than 10 times, with exceptional yield. Furthermore, the commercially accessible anticancer drug Elacestrant can be readily produced using this protocol. Full article

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

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30 pages, 3225 KiB

Open AccessArticle

Obtention and Products Distribution of Bioliquid from Catalytic Pyrolysis of Tomato Plant Waste

by José L. Buitrago, Leticia J. Méndez, Juan J. Musci, Juan A. Cecilia, Daniel Ballesteros-Plata, Enrique Rodríguez-Castellón, Mónica L. Casella, Luis R. Pizzio and Ileana D. Lick

Catalysts 2025, 15(4), 388; https://doi.org/10.3390/catal15040388 - 17 Apr 2025

Viewed by 168

Abstract

The use of tomato plant residues (i.e., stems, leaves, etc.) as a substrate for catalytic pyrolysis of biomass was investigated. A comprehensive study was conducted to investigate the impact of catalysts on the performance of different pyrolysis fractions (i.e., gas, biosolid, waxes, and [...] Read more.

The use of tomato plant residues (i.e., stems, leaves, etc.) as a substrate for catalytic pyrolysis of biomass was investigated. A comprehensive study was conducted to investigate the impact of catalysts on the performance of different pyrolysis fractions (i.e., gas, biosolid, waxes, and bioliquid) as well as the distribution of products within the bioliquid. The catalysts employed in this study were derived from two distinct types of zirconia. The first type was synthesized by a conventional sol-gel method, while the second type was prepared with a modified method aimed at improving the presence of mesopores. This modification involved the incorporation of Pluronic 123. These materials were designated ZrO₂ and ZrO₂P25, respectively. Both types of zirconia were used as supports for tungstophosphoric acid (H₃PW₁₂O₄₀, TPA), a heteropolyacid with a Keggin structure, in the preparation of catalysts with strong acid sites. The results demonstrated that the bioliquid yield of the non-catalytic fast pyrolysis of tomato plant waste was approximately 23% and that the obtained bioliquid contained a wide variety of molecules, which were detected and quantified by GC-MS. In the presence of the catalysts, both the bioliquid yield and the distribution of bioliquid products were substantially modified. Furthermore, the possible sugar degradation pathways leading to the formation of the molecules present in the pyrolytic bioliquids were thoroughly examined. The results obtained from this study indicate that the physicochemical characteristics of the catalysts, specifically their pore size and acidity, have a significant impact on the selectivity of the catalytic processes towards valuable molecules, including anhydro-sugars and furanic derivatives such as furfural and furfuryl alcohol. Full article

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

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22 pages, 8217 KiB

Open AccessFeature PaperReview

Cellulosome Systems in the Digestive Tract: Underexplored Enzymatic Machine for Lignocellulose Bioconversion

by Jiajing Qi, Mengke Zhang, Chao Chen, Yingang Feng and Jinsong Xuan

Catalysts 2025, 15(4), 387; https://doi.org/10.3390/catal15040387 - 16 Apr 2025

Viewed by 220

Abstract

Cellulosomes are sophisticated multi-enzyme complexes synthesized and secreted by anaerobic microorganisms, characterized by intricate structural components and highly organized modular assembly mechanisms. These complexes play a pivotal role in the efficient degradation of lignocellulosic biomass, significantly enhancing its bioconversion efficiency, and are thus [...] Read more.

Cellulosomes are sophisticated multi-enzyme complexes synthesized and secreted by anaerobic microorganisms, characterized by intricate structural components and highly organized modular assembly mechanisms. These complexes play a pivotal role in the efficient degradation of lignocellulosic biomass, significantly enhancing its bioconversion efficiency, and are thus regarded as invaluable enzymatic molecular machines. Cellulosomes are not only prevalent in anaerobic bacteria from soil and compost environments but are also integral to the digestive systems of herbivorous animals, primates and termites. The cellulosomes produced by digestive tract microbiota exhibit unique properties, providing novel enzymes and protein modules that are instrumental in biomass conversion and synthetic biology, thereby showcasing substantial application potential. Despite their promise, the isolation and cultivation of digestive tract microorganisms that produce cellulosomes present significant challenges. Additionally, the lack of comprehensive genetic and biochemical studies has impeded a thorough understanding of these cellulosomes, leaving them largely underexplored. This paper provides a comprehensive overview of the digestive tract cellulosome system, with a particular focus on the structural and functional attributes of cellulosomes in various animal digestive tracts. It also discusses the application prospects of digestive tract cellulosomes, highlighting their potential as a treasure in diverse fields. Full article

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

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13 pages, 2419 KiB

Open AccessArticle

Enhancement of Enzyme Activity by Alternating Magnetic Field and Near-Infrared Irradiation

by Fang Wang, Yuchen Liu, Qikai Dong, Zihan Li, Senrong Liang, Tianyi Zhang, Liangtao Xu and Renjun Gao

Catalysts 2025, 15(4), 386; https://doi.org/10.3390/catal15040386 - 16 Apr 2025

Viewed by 173

Abstract

The enhancement of enzyme activity has garnered significant attention in biotransformation processes and applications. This enhancement is achieved through the use of specific nanomaterials (NMs) with unique physicochemical characteristics responsive to external stimuli. In this study, an enzyme–Fe₃O₄ nano-biocatalytic system [...] Read more.

The enhancement of enzyme activity has garnered significant attention in biotransformation processes and applications. This enhancement is achieved through the use of specific nanomaterials (NMs) with unique physicochemical characteristics responsive to external stimuli. In this study, an enzyme–Fe₃O₄ nano-biocatalytic system (NBS) was developed to enable real-time activation of enzymatic catalysis under alternating magnetic field (AMF) and near-infrared (NIR) irradiation using dual-functional Fe₃O₄ magnetic nanoparticles (MNPs). When exposed to an AMF, Fe₃O₄ MNPs generate molecular vibrations through mechanisms such as Néel or Brown relaxation while acting as a photothermal agent in response to NIR irradiation. The synergistic effect of AMF and NIR irradiation significantly enhanced energy transfer between the enzyme and Fe₃O₄ MNPs, resulting in a maximum 4.3-fold increase in enzyme activity. Furthermore, the system reduced aldol reaction time by 66% (from 4 h to 1.5 h) while achieving 90% product yield. Additionally, factors such as nanoparticle size and NIR power were found to play a critical role in the efficiency of this real-time regulation strategy. The results also demonstrate that the enzyme–Fe₃O₄ nanocomposites (NCs) significantly enhanced catalytic efficiency and reduced the reaction time for aldol reactions. This study demonstrates an efficient NBS controlled via the synergistic effects of AMF and NIR irradiation, enabling spatiotemporal control of biochemical reactions. This work also provides a breakthrough strategy for dynamic biocatalysis, with potential applications in industrial biomanufacturing, on-demand drug synthesis, and precision nanomedicine. Full article

(This article belongs to the Special Issue Enzyme Catalysis and Enzyme Engineering)

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22 pages, 3114 KiB

Open AccessArticle

Nickel-Decorated Carbocatalysts for the UV-Driven Photodegradation of Rhodamine B

by Juan Matos, Rory A. Smith, Ruby Bello, Po S. Poon, Rodrigo Segura-del-Río, Néstor Escalona and Svetlana Bashkova

Catalysts 2025, 15(4), 385; https://doi.org/10.3390/catal15040385 - 16 Apr 2025

Viewed by 106

Abstract

Nickel-decorated carbocatalysts were synthesized by the evaporation-induced self-assembly (EISA) method. The influence of the metal content and pyrolysis temperature upon the photoactivity was assessed through rhodamine B degradation under UV irradiation. The characterization revealed a mesoporous framework with a granular morphology composed of [...] Read more.

Nickel-decorated carbocatalysts were synthesized by the evaporation-induced self-assembly (EISA) method. The influence of the metal content and pyrolysis temperature upon the photoactivity was assessed through rhodamine B degradation under UV irradiation. The characterization revealed a mesoporous framework with a granular morphology composed of amorphous carbon, where the pyrolysis temperature influenced the metal dispersion on the carbon surface. The primary metallic phases consisted of elemental nickel crystallites and nickel carbide phases. The kinetic parameters for adsorption and dye photodegradation under UV irradiation were determined and compared to TiO₂-P25. Correlations were found between the adsorption parameters, photocatalytic activity, and nickel content, the pyrolysis method (one-step vs. two-step pyrolysis), and the pyrolysis temperature. The sample with a 1:1:0.25 tannin/Pluronic^®F-127/Ni weight ratio pyrolyzed at 700 °C exhibited the highest photoactivity, achieving rhodamine B degradation rates up to 68 and 2.5 times greater than photolysis and TiO₂-P25. In terms of the normalized weight of the catalysts, it can be concluded that the present Ni-based catalysts are up to two orders of magnitude more photoactive than TiO₂-P25 under UV irradiation, opening a door for indoor UV-driven photoreactors. These findings demonstrate that the EISA method is an effective, low-cost, and ecofriendly approach for synthesizing Ni-decorated carbocatalysts. Full article

(This article belongs to the Special Issue Hybrid Materials, Semiconductors and Carbon Photocatalysis)

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15 pages, 2835 KiB

Open AccessArticle

Template–Free–Induced Synthesis of an Fe–N–C Electrocatalyst with Porous Yolk–Shell Structure Towards Oxygen Reduction Reaction

by Lili Wang, Li Chen, Zhiwen Li, Shaohua Zhang, Hezhen Wang, Ling Xu and Yan Xie

Catalysts 2025, 15(4), 384; https://doi.org/10.3390/catal15040384 - 16 Apr 2025

Viewed by 168

Abstract

Significant research has focused on cost–effective, highly active, and exceptionally stable non–noble metal electrocatalysts (NNMEs) to boost the performance of the oxygen reduction reaction (ORR). Of note, the development of design and synthesis of Fe–N–C electrocatalysts is essential but remains challenging. Herein, the [...] Read more.

Significant research has focused on cost–effective, highly active, and exceptionally stable non–noble metal electrocatalysts (NNMEs) to boost the performance of the oxygen reduction reaction (ORR). Of note, the development of design and synthesis of Fe–N–C electrocatalysts is essential but remains challenging. Herein, the Fe and N co–doped porous carbon material with a yolk–shell (YS) structure, termed SA–H₂TPyP@PDA–Fe (900), was fabricated by self–assembly of metal–free porphyrin as a yolk and polymerization of dopamine as a shell with an addition of iron salts, followed by the high–temperature pyrolysis and acid–leaching. As a result, active sites, like FeN₄ and N–doped C, within rich porous YS carbon structures, play an important role for ORR in an alkaline media. The SA–H₂TPyP@PDA–Fe (900) electrocatalyst shows positive ORR performances than those of SA–H₂TPyP (900) and SA–H₂TPyP@PDA (900), indicating the dominating function of the YS carbon structure decorated with Fe–based species. This efficient route of template–free–induced preparation of the YS structure discovers the design and synthesis of NNMEs for ORR. Full article

(This article belongs to the Special Issue Electrocatalytic Hydrogen and Oxygen Evolution Reaction)

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16 pages, 3060 KiB

Open AccessArticle

High-Pressure CO₂ Photoreduction, Flame Spray Pyrolysis and Type-II Heterojunctions: A Promising Synergy

by Matteo Tommasi, Alice Gramegna, Simge Naz Degerli, Federico Galli and Ilenia Rossetti

Catalysts 2025, 15(4), 383; https://doi.org/10.3390/catal15040383 - 16 Apr 2025

Viewed by 184

Abstract

In this work, three catalysts, TiO₂, WO₃ and TiO₂/WO₃, have been synthesized through flame spray pyrolysis synthesis (FSP) and have been tested for CO₂ photoreduction. The catalysts were fully characterized by XRD, DRS UV–Vis, N [...] Read more.

In this work, three catalysts, TiO₂, WO₃ and TiO₂/WO₃, have been synthesized through flame spray pyrolysis synthesis (FSP) and have been tested for CO₂ photoreduction. The catalysts were fully characterized by XRD, DRS UV–Vis, N₂ physisorption and SEM. Experimental tests were performed in a one-of-a-kind high-pressure reactor at 18 bar. TiO₂ P25 was used as a benchmark to compare the productivities of the newly synthetized catalysts. The two single oxides showed comparable productivities, both slightly lower than the P25 reference value (ca. 17 mol/kg_cat·h). The mixed oxide, TiO₂/WO₃, instead showed an impressive productivity of formic acid with 36 mol/kg_cat·h, which is around 2.5 times higher than both of the single oxides alone. The formation of a type-II heterojunction has been confirmed through DRS analysis. The remarkable productivity demonstrates how FSP synthesis can be a crucial tool to obtain highly active and stable photocatalysts. This approach has already been successfully scaled up for the industrial production of various catalysts, showcasing its versatility and efficiency. Full article

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

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15 pages, 2470 KiB

Open AccessFeature PaperArticle

Geometric Matching Effect Induced High Dispersion of Na₂WO₄ Nanocluster on Cristobalite Support for Efficient Methyl Chloride-to-Vinyl Chloride Conversion

by Nan Lu, Yifeng Shi, Yutao Ren, Yue Wang, Xinyi Sun, Zejing Wei, Xutao Chen and Jie Fan

Catalysts 2025, 15(4), 382; https://doi.org/10.3390/catal15040382 - 16 Apr 2025

Viewed by 184

Abstract

The oxidative coupling of methyl chloride (CH₃Cl) to vinyl chloride (C₂H₃Cl) (MCTV) represents a promising yet challenging direct conversion route for C₂H₃Cl production. In this study, a novel catalyst, cristobalite silica, supported Na [...] Read more.

The oxidative coupling of methyl chloride (CH₃Cl) to vinyl chloride (C₂H₃Cl) (MCTV) represents a promising yet challenging direct conversion route for C₂H₃Cl production. In this study, a novel catalyst, cristobalite silica, supported Na₂WO₄ nanoclusters, was fabricated by calcining an intermediate composite composed by β-zeolite and sodium tungstate (Na₂WO₄). The pore structure of this β-zeolite possesses a regular shape and suitable size distribution, providing an accurate geometric matching effect for Na₂WO₄ to homogeneously distribute in the entire β-zeolite matrix with high loading. Accordingly, the excellent dispersity of Na₂WO₄ nanocluster active sites is well maintained even after calcining at 750 °C, and the microporous β-zeolite matrix is completely converted to dense cristobalite phase silica after the calcination. The high-loading and well-dispersed Na₂WO₄ nanocluster leads to a superior performance in MCTV with a CH₃Cl conversion of 81.5%, a C₂H₃Cl selectivity of 42.4%, and a C₂H₃Cl yield of 34.6%. Notably, the catalyst exhibits remarkable stability during the catalytic process. Full article

(This article belongs to the Collection Highly Dispersed Nanocatalysts)

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30 pages, 2863 KiB

Open AccessReview

Occurrence, Ecotoxicity, and Photocatalytic Remediation of Antiretroviral Drugs in Global Surface Water Matrices

by Phephile Ngwenya, Lehlogonolo S. Tabana, Shepherd M. Tichapondwa and Evans M. N. Chirwa

Catalysts 2025, 15(4), 381; https://doi.org/10.3390/catal15040381 - 15 Apr 2025

Viewed by 441

Abstract

The increasing presence of pharmaceuticals, particularly antiretroviral drugs (ARVs), in wastewater has raised concerns regarding their environmental and health impacts. Photocatalysis, driven by advanced photocatalysts, such as coloured TiO₂, ZnO, and composites with carbon-based materials, has shown promise as an effective [...] Read more.

The increasing presence of pharmaceuticals, particularly antiretroviral drugs (ARVs), in wastewater has raised concerns regarding their environmental and health impacts. Photocatalysis, driven by advanced photocatalysts, such as coloured TiO₂, ZnO, and composites with carbon-based materials, has shown promise as an effective method for degrading these pollutants. Despite significant laboratory-scale success, challenges remain in scaling this technology for real-world applications, particularly in terms of photocatalyst stability, the formation of toxic degradation by-products, and economic feasibility. This paper explores the current state of photocatalytic degradation for ARVDs, emphasizing the need for further research into degradation pathways, the development of more efficient and cost-effective photocatalysts, and the integration of photocatalysis into hybrid treatment systems. The future of photocatalysis in wastewater treatment hinges on improving scalability, reactor design, and hybrid systems that combine photocatalysis with traditional treatment methods to ensure comprehensive pollutant removal. Innovations in catalyst design and reactor optimization are essential for advancing photocatalysis as a viable solution for large-scale wastewater treatment. Full article

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

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17 pages, 8294 KiB

Open AccessArticle

Aqueous Gel-Casting Synthesis and the Characterization of Cobalt Oxide as a Catalyst Precursor for Sodium Borohydride Hydrolysis

by Lan Zhang, Zhihua Deng, Bin Miao, Hongquan He, Chee Kok Poh, Lili Zhang and Siew Hwa Chan

Catalysts 2025, 15(4), 380; https://doi.org/10.3390/catal15040380 - 14 Apr 2025

Viewed by 241

Abstract

Aqueous gel-casting provides a cost-effective and scalable approach for synthesizing nano-spherical Co₃O₄ powders, enabling precise control over particle morphology. In this study, Co₃O₄ powders were prepared using this method and evaluated as a catalyst precursor for the [...] Read more.

Aqueous gel-casting provides a cost-effective and scalable approach for synthesizing nano-spherical Co₃O₄ powders, enabling precise control over particle morphology. In this study, Co₃O₄ powders were prepared using this method and evaluated as a catalyst precursor for the hydrolysis of sodium borohydride (NaBH₄). The effects of the monomer (acrylamide, AM)-to-metal molar ratio and initiator content (ammonium persulphate, APS) on particle size and catalytic performance were systematically explored. X-ray diffraction (XRD) analysis confirmed the formation of the Co₃O₄ phase at 400 °C, while transmission electron microscopy (TEM) images revealed particle sizes ranging from 16 to 85 nm, with higher AM and APS concentrations promoting finer particles. The optimized catalyst achieved a high hydrogen generation rate (HGR) of 28.13 L min⁻¹·cat.⁻¹, demonstrating excellent catalytic activity. Moreover, in situ-formed cobalt boride, derived from Co₃O₄ calcined at 600 °C for 2 h, exhibited an activation energy of 51.81 kJ mol⁻¹, comparable to Ru-based catalysts. This study underscores the aqueous gel-casting technique as a promising strategy for synthesizing efficient and low-cost hydrogen generation catalysts, offering an alternative to noble metal-based materials. Full article

(This article belongs to the Special Issue Catalytic Processes for Green Hydrogen Production)

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17 pages, 2664 KiB

Open AccessArticle

Optimization of Acid-Catalyzed Hydrolysis and Simultaneous Saccharification and Fermentation for Enhanced Ethanol Production from Sweet Stalk Sorghum

by Torpong Kreetachat, Nopparat Suriyachai, Punjarat Khongchamnan, Kowit Suwannahong, Surachai Wongcharee, Chainarong Sakulthaew, Chanat Chokejaroenrat and Saksit Imman

Catalysts 2025, 15(4), 379; https://doi.org/10.3390/catal15040379 - 13 Apr 2025

Viewed by 243

Abstract

This study aims to identify the best conditions for liquid hot water pretreatment (LHW) of sweet stalk sorghum and the optimization method using the response surface method (RSM) with varying parameters, including temperature, reaction time, and acid catalysts, to enhance the enzymatic hydrolysis [...] Read more.

This study aims to identify the best conditions for liquid hot water pretreatment (LHW) of sweet stalk sorghum and the optimization method using the response surface method (RSM) with varying parameters, including temperature, reaction time, and acid catalysts, to enhance the enzymatic hydrolysis of pretreated sweet stalk sorghum. This study presents a novel approach by optimizing LHW pretreatment using RSM to maximize the glucose yield and minimize sugar degradation, in contrast to the widely used method of sulfuric acid hydrolysis combined with SSF. The goal is to achieve the highest glucose yield for ethanol production under optimal conditions. The results show that after the LHW pretreatment under optimal conditions, the optimal actual values have the highest glucose yield of 91.09% in a solid fraction at a sulfuric acid catalyst concentration of 0.90% with a pretreatment temperature of 110 °C for 90 min. The results of the statistical analysis of the glucose yield show an R-squared value of 0.9964 or 99.64%, which is statistically significant. In addition, the optimized pretreatment conditions significantly improved the accessibility of the enzyme. Pretreatment for ethanol production in sweet stalk sorghum samples was carried out with an H₂SO₄ catalyst concentration of 0.90% using the SSF method with the yeast strain S. cerevisiae. The results show that during the fermentation period of 0–96 h, the maximum ethanol concentration of 23.1 g/L occurred at 72 h under 25 FPU/g substrate at pH 4.8 and decreased 72 h after fermentation. In conclusion, sweet stalk sorghum is a promising candidate for ethanol production due to its high glucose yield and efficient enzymatic hydrolysis, making it a viable alternative for biomass-based energy production. Full article

(This article belongs to the Special Issue Advanced Catalysts Design and Catalytic Conversion of Biomass to High-Value Products)

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30 pages, 6140 KiB

Open AccessArticle

Aggregated Catalyst Physicochemical Descriptor-Driven Machine Learning for Catalyst Optimization: Insights into Oxidative-Coupling-of-Methane Dynamics and C2 Yields

by Mohamed Ezz, Ayman Mohamed Mostafa, Alaa S. Alaerjan, Hisham Allahem, Bader Aldughayfiq, Hassan M. A. Hassan and Rasha M. K. Mohamed

Catalysts 2025, 15(4), 378; https://doi.org/10.3390/catal15040378 - 13 Apr 2025

Viewed by 279

Abstract

This study focuses on optimizing C2 yields in the oxidative coupling of methane (OCM), a pivotal process for sustainable chemical production. By harnessing advanced machine learning (ML) techniques, this research aimed to predict C2 yields and identify the factors that drive catalytic performance. [...] Read more.

This study focuses on optimizing C2 yields in the oxidative coupling of methane (OCM), a pivotal process for sustainable chemical production. By harnessing advanced machine learning (ML) techniques, this research aimed to predict C2 yields and identify the factors that drive catalytic performance. The Extra Trees Regressor emerged as the most effective model after a comprehensive evaluation across multiple datasets and methodologies. Key to the method was the use of an innovative Aggregated Catalyst Physicochemical Descriptor (ACPD) and stratified cross-validation, which effectively addressed feature complexity and target skewness. Hyperparameter optimization using Modified Sequential Model-Based Optimization (SMBO) further enhanced the model’s performance, achieving optimized R² values of 61.7%, 75.9%, and 92.0% for datasets A, B, and C, respectively, with corresponding reductions in the Mean Squared Error (MSE) and Root Mean Squared Error (RMSE). Additionally, SHAP (SHapley Additive exPlanations) analysis provided a detailed understanding of the model’s decision-making process, revealing the relative importance of individual features and their contributions to the predictive outcomes. This research not only achieved state-of-the-art predictive accuracy, but also deepened our understanding of the underlying chemical dynamics, offering practical guidance for catalyst design and operational optimization. These findings mark a significant advancement in catalysis, paving the way for future innovations in sustainable chemical manufacturing. Full article

(This article belongs to the Section Computational Catalysis)

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13 pages, 5748 KiB

Open AccessArticle

Theoretical Study of Ni- and Cu-Doped Molybdenum Ditelluride Electrocatalysts for Carbon Dioxide Reduction to Formic Acid and Carbon Monoxide

by Bin Zhao, Junyou Wang, Rui Wan and Zhongyao Li

Catalysts 2025, 15(4), 377; https://doi.org/10.3390/catal15040377 - 12 Apr 2025

Viewed by 283

Abstract

Under mild conditions, the effective conversion of carbon dioxide (CO₂) into formic acid (HCOOH) and carbon monoxide (CO) represents a promising avenue for mitigating greenhouse gas emissions and addressing energy crises. In this work, we analyzed the electro-catalytic activities of six [...] Read more.

Under mild conditions, the effective conversion of carbon dioxide (CO₂) into formic acid (HCOOH) and carbon monoxide (CO) represents a promising avenue for mitigating greenhouse gas emissions and addressing energy crises. In this work, we analyzed the electro-catalytic activities of six metals (Ti, Fe, Ni, Cu, Zn, and Cr) anchored on monolayer molybdenum telluride (TM@MoTe₂) for the CO₂ reduction reaction (CO₂RR) from CO₂ to HCOOH and CO. Compared to the reversible hydrogen electrode, the limiting potential for HCOOH production on Ni@MoTe₂ is only about −0.38 V, and it is only about −0.20 V for the CO production on Cu@MoTe₂. The limiting potential is concerned with the free energies of *OCHO and *COOH. Both the CO₂RRs suppress the competing hydrogen evolution reaction (HER) and exhibit good selectivity for the desired reaction products. These features enable the efficient conversion of CO₂ into HCOOH on Ni@MoTe₂ or CO on Cu@MoTe₂. Our calculations could provide valuable insights for the design and synthesis of high-performance catalysts based on MoTe₂. Full article

(This article belongs to the Section Electrocatalysis)

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20 pages, 7493 KiB

Open AccessArticle

Carbon-Coated Magnetic Catalysts for Enhanced Degradation of Nitrophenols: Stability and Efficiency in Catalytic Wet Peroxide Oxidation

by Arthur P. Baldo, Ana Júlia B. Bezerra, Adriano S. Silva, Ana Paula Ferreira, Fernanda F. Roman, Ihsan Çaha, Manuel Bañobre-López, Francis Leonard Deepak and Helder T. Gomes

Catalysts 2025, 15(4), 376; https://doi.org/10.3390/catal15040376 - 11 Apr 2025

Viewed by 256

Abstract

Nitrophenols are persistent organic pollutants that pose serious environmental and health risks due to their toxic and lipophilic nature. Their persistence arises from strong aromatic stability and resistance to biodegradation, while their lipophilicity facilitates bioaccumulation, exacerbating ecological and human health concerns. To address [...] Read more.

Nitrophenols are persistent organic pollutants that pose serious environmental and health risks due to their toxic and lipophilic nature. Their persistence arises from strong aromatic stability and resistance to biodegradation, while their lipophilicity facilitates bioaccumulation, exacerbating ecological and human health concerns. To address this challenge, this study focuses on the synthesis and characterization of two different types of hybrid multi-core magnetic catalysts: (i) cobalt ferrite (Co-Fe₂O₄), which exhibits ferrimagnetic properties, and (ii) magnetite (Fe₃O₄), which demonstrates close superparamagnetic behavior and is coated with a novel and less hazardous phloroglucinol–glyoxal-derived resin. This approach aims to enhance catalytic efficiency while reducing the environmental impact, offering a sustainable solution for the degradation of nitrophenols in aqueous matrices. Transmission electron microscopy (TEM) images revealed the formation of a multi-core shell structure, with carbon layer sizes of 6.6 ± 0.7 nm for cobalt ferrite and 4.2 ± 0.2 nm for magnetite. The catalysts were designed to enhance the stability and performance in catalytic wet peroxide oxidation (CWPO) processes using sol–gel and solution combustion synthesis methods, respectively. In experiments of single-component degradation, the carbon-coated cobalt ferrite (CoFe@C) catalyst achieved 90% removal of 2-nitrophenol (2-NP) and 96% of 4-nitrophenol (4-NP), while carbon-coated magnetite (Fe₃O₄@C) demonstrated similar efficiency, with 86% removal of 2-NP and 94% of 4-NP. In the multi-component system, CoFe@C exhibited the highest catalytic activity, reaching 96% removal of 2-NP, 99% of 4-NP, and 91% decomposition of H₂O₂. No leaching of iron was detected in the coated catalysts, whereas the uncoated materials exhibited similar and significant leaching (CoFe: 5.66 mg/L, Fe₃O₄: 12 mg/L) in the single- and multi-component system. This study underscores the potential of hybrid magnetic catalysts for sustainable environmental remediation, demonstrating a dual-function mechanism that enhances catalytic activity and structural stability. Full article

(This article belongs to the Special Issue Carbon-Based Catalysts to Address Environmental Challenges)

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