Catalysts

12 pages, 1732 KiB

Open AccessArticle

MOF-Derived Electrocatalysts for High-Efficiency Hydrogen Production via Water Electrolysis

by Nan Zhang, Pengfei Cui, Jinrong Zhang and Yang Qiao

Catalysts 2025, 15(6), 579; https://doi.org/10.3390/catal15060579 - 10 Jun 2025

Water electrolysis for hydrogen production has garnered significant attention in the context of increasing global energy demands and the “dual-carbon” strategy. However, practical implementation is hindered by challenges such as high overpotentials, high catalysts costs, and insufficient catalytic activity. In this study, three [...] Read more.

Water electrolysis for hydrogen production has garnered significant attention in the context of increasing global energy demands and the “dual-carbon” strategy. However, practical implementation is hindered by challenges such as high overpotentials, high catalysts costs, and insufficient catalytic activity. In this study, three mono and bimetallic metal−organic framework (MOFs)-derived electrocatalysts, Fe-MOFs, Fe/Co-MOFs, and Fe/Mn-MOFs, were synthesized via a one-step hydrothermal method, using nitro-terephthalic acid (NO₂-BDC) as the ligand and N,N-dimethylacetamide (DMA) as the solvent. Electrochemical tests demonstrated that the Fe/Mn-MOFs catalyst exhibited superior performance, achieving an overpotential of 232.8 mV and a Tafel slope of 59.6 mV·dec⁻¹, alongside the largest electrochemical active surface area (ECSA). In contrast, Fe/Co-MOFs displayed moderate catalytic activity, while Fe-MOFs exhibited the lowest efficiency. Stability tests revealed that Fe/Mn-MOFs retained 92.3% of its initial current density after 50 h of continuous operation, highlighting its excellent durability for the oxygen evolution reaction (OER). These findings emphasize the enhanced catalytic performance of bimetallic MOFs compared to monometallic counterparts and provide valuable insights for the development of high-efficiency MOF-based electrocatalysts for sustainable hydrogen production. Full article

(This article belongs to the Section Catalytic Materials)

19 pages, 2494 KiB

Open AccessArticle

Mesoporous MCM-48 and MCM-41 Silicas Modified with Copper by ADP Method as Effective Catalysts for Low-Temperature NH₃-SCR—The Role of Synthesis Conditions and Associated Reactions

by Aleksandra Gomułka, Andrzej Kowalczyk, Izabela Majewska, Pegie Cool and Lucjan Chmielarz

Catalysts 2025, 15(6), 578; https://doi.org/10.3390/catal15060578 - 10 Jun 2025

Abstract

Mesoporous silicas of MCM-41 and MCM-48 types were synthesized and modified with copper using the ammonia-driven deposition precipitation (ADP) method, resulting in highly dispersed copper species. Samples with varying copper loadings were thoroughly characterized in terms of their porous structure, metal content, copper [...] Read more.

Mesoporous silicas of MCM-41 and MCM-48 types were synthesized and modified with copper using the ammonia-driven deposition precipitation (ADP) method, resulting in highly dispersed copper species. Samples with varying copper loadings were thoroughly characterized in terms of their porous structure, metal content, copper species’ aggregation, and the stability of deposited forms under reaction conditions. Copper-modified mesoporous silicas exhibited excellent catalytic performance in the low-temperature NH₃-SCR process. Their activity in NO to NO₂ oxidation suggests that the fast-SCR pathway plays a significant role in NO_x conversion at low temperatures. However, direct ammonia oxidation limited SCR efficiency at higher temperatures. These findings demonstrate the potential of ADP-modified copper–silica catalysts for effective and selective NO_x removal under low-temperature conditions. Full article

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

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15 pages, 2435 KiB

Open AccessFeature PaperArticle

Effects of Mg on CO₂ Hydrogenation on PtCoAl Catalysts

by Yiming He, Jian Chen, Yunjie Xie, Qingsong Hu, Linjun Wang, Yi Liu, Xiaolu Xu, Bowen Xu and Feng Zeng

Catalysts 2025, 15(6), 577; https://doi.org/10.3390/catal15060577 - 10 Jun 2025

Abstract

The incorporation of Mg into PtCoAl catalysts was systematically investigated to elucidate its impact on the physicochemical properties and catalytic performance in CO₂ hydrogenation. A series of x% Mg-PtCoAl catalysts with varying Mg contents were synthesized and evaluated for CO₂ hydrogenation. [...] Read more.

The incorporation of Mg into PtCoAl catalysts was systematically investigated to elucidate its impact on the physicochemical properties and catalytic performance in CO₂ hydrogenation. A series of x% Mg-PtCoAl catalysts with varying Mg contents were synthesized and evaluated for CO₂ hydrogenation. The results demonstrate that Mg acts as a promoter by strengthening metal–support interactions, slightly suppressing reducibility while markedly enhancing hydrogen adsorption capacity and the number of basic sites. Additionally, an optimal Mg content increases the proportion of weak basic sites, which synergistically facilitates CO₂ activation in conjunction with weakly adsorbed hydrogen. The effects of Pt and Mg loadings were further investigated using different precipitants, revealing that moderate loadings (Pt: 0.11–0.12 mmol g_cat⁻¹, Mg: 0.08–0.10 mmol g_cat⁻¹) most effectively enhance catalytic activity. Under an initial pressure of 4 MPa and 180 °C, the Mg-modified PtCoAl catalyst achieved a methane productivity of 51.4 mmol g_cat⁻¹ h⁻¹ and an alcohol productivity of 0.895 mmol g_cat⁻¹ h⁻¹, with higher alcohols accounting for 33.6% of the total alcohol products. This study underscores the pivotal role of Mg in tuning surface basicity and hydrogen adsorption properties, offering valuable insights for the rational design of efficient CO₂ hydrogenation catalysts. Full article

(This article belongs to the Special Issue Trends and Prospects in Catalysis for Sustainable CO₂ Conversion)

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15 pages, 3620 KiB

Open AccessFeature PaperArticle

ZIF-L/PBA-Derived Self-Supporting Ni-Doped CoFeP Electrocatalysts for Bifunctional Water Splitting

by Lanqi Wang, Hui Ni, Jianing Yu, Jingyuan Zhang and Bin Zhao

Catalysts 2025, 15(6), 576; https://doi.org/10.3390/catal15060576 - 10 Jun 2025

Abstract

In recent years, transition metal-based catalytic materials have garnered considerable attention, particularly those exhibiting high catalytic efficiency toward both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In this work, a self-supporting ternary transition metal phosphide (CoFeNi_0.2P) with a [...] Read more.

In recent years, transition metal-based catalytic materials have garnered considerable attention, particularly those exhibiting high catalytic efficiency toward both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In this work, a self-supporting ternary transition metal phosphide (CoFeNi_0.2P) with a hierarchical structure was synthesized using the Prussian blue analogue (PBA)/zeolitic imidazolate framework-L (ZIF-L) template. Benefiting from the hierarchical structure of the PBA/ZIF-L precursor and the electronic structure modulation induced by Ni doping, the resulting CoFeNi_0.2P demonstrates impressive bifunctional electrocatalytic activity. Specifically, in 1 M KOH electrolyte, the CoFeNi_0.2P catalyst requires an overpotential of only 88 mV to deliver 10 mA cm⁻² for the HER and 248 mV to achieve 50 mA cm⁻² for the OER. Moreover, it demonstrates satisfactory stability toward both the HER and OER. When integrated into a two-electrode electrolyzer, CoFeNi_0.2P enables a current density of 10 mA cm⁻² at a cell voltage of 1.59 V, maintaining robust performance for over 25 h. This study provides a feasible strategy for the rational design of hierarchical electrocatalysts for efficient overall water splitting. Full article

(This article belongs to the Special Issue Two-Dimensional (2D) Materials in Catalysis)

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12 pages, 1019 KiB

Open AccessArticle

Purification and Characterization of a Protease Using Aspergillus oryzae Under Submerged Fermentation Using Dairy By-Products as a Substrate

by Aline Ferreira Sobral, Diego Gomes Ramos, Bárbara Cibele Souza Lima, Tatiana Pereira Shiu Lin Liu, Maria Rafaele Oliveira Bezerra da Silva, Luiz Henrique Svintiskas Lino, Kethylen Barbara Barbosa Cardoso, Wendell Wagner Campos Albuquerque, Thiago Pajeú Nascimento and Romero Marcos Pedrosa Brandão Costa

Catalysts 2025, 15(6), 575; https://doi.org/10.3390/catal15060575 - 10 Jun 2025

Abstract

Whey, a large-scale dairy industry by-product, can be converted into whey protein concentrate (WPC), providing a cost-effective nutrient-rich substrate for microbial fermentation. We investigated protease production by Aspergillus oryzae using WPC as the sole substrate in submerged fermentation. Following fermentation, the protease was [...] Read more.

Whey, a large-scale dairy industry by-product, can be converted into whey protein concentrate (WPC), providing a cost-effective nutrient-rich substrate for microbial fermentation. We investigated protease production by Aspergillus oryzae using WPC as the sole substrate in submerged fermentation. Following fermentation, the protease was purified sequentially from the crude extract by salting-out, which yielded a substantial purification factor (~39), and subsequent ion-exchange chromatography. The non-adsorbed chromatographic fraction showed the highest protease activity (92.6 U/mL) and revealed one main protein band ~45 kDa via SDS-PAGE. Enzyme characterization demonstrated activity across neutral-to-alkaline conditions, optimal at pH 9.0 and 37 °C, with stability maintained between 30 °C and 37 °C. The enzyme was classified as a serine protease based on strong inhibition by PMSF and SDS; its activity was also inhibited by Zn²⁺, Mg²⁺, and K⁺, but enhanced by Ca²⁺. This work validates WPC as an efficient substrate for protease production by A. oryzae and presents a promising strategy for valorizing industrial by-products through sustainable biotechnology. Full article

(This article belongs to the Special Issue Enzyme Catalysis: Innovations and Applications in Sustainable Chemistry)

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8 pages, 2202 KiB

Open AccessConference Report

The 11th International Congress on Biocatalysis (biocat2024), Hamburg, Germany, 25–29 August 2024

by Victoria Bueschler, Paul Bubenheim, Barbara Klippel, Ana Malvis Romero, Daniel Ohde, Anna-Lena Heins, Johannes Gescher, Franziska Rohweder and Andreas Liese

Catalysts 2025, 15(6), 574; https://doi.org/10.3390/catal15060574 (registering DOI) - 10 Jun 2025

Abstract

The “11th International Congress on Biocatalysis (biocat2024)” was part of a biennial series that unites the fields of biology and chemistry, attracting researchers from the life sciences, engineering, and computer science. This international forum provides an opportunity for scientists worldwide to connect, seek [...] Read more.

The “11th International Congress on Biocatalysis (biocat2024)” was part of a biennial series that unites the fields of biology and chemistry, attracting researchers from the life sciences, engineering, and computer science. This international forum provides an opportunity for scientists worldwide to connect, seek collaboration for future projects, and gain insights into contemporary topics and innovative techniques. Biocat covers a range of compelling subjects and recent advancements in biocatalysis, including enzyme discovery, evolution, and applications. This congress focused on six key topics: AI and computational methods, structure–function analysis and enzyme engineering, enzymatic and whole-cell biotransformations, reaction cascades (electro-, chemo-, and photoenzymatic synergies), bioprocess engineering and the design of smart reactors, and facing climate change through sustainability and a circular bioeconomy. In 2024, we welcomed 344 expert delegates alongside 21 internal attendees, including 154 women and 1 non-binary participant, bringing the total number of participants to an impressive 365. Established researchers and emerging scientists from academia and industry delivered a total of 119 presentations, comprising 59 standard lectures, 60 lightning talks, and 195 posters. Six industry exhibitors showcased their latest products and services, providing an excellent opportunity to strengthen the connection between science and industry. Furthermore, the biocat award, recognized as one of the most prestigious honors in biotechnology, was presented for the eleventh time in the categories of “Science in Academia”, “Lifetime Achievement,” and “Industry”. Full article

(This article belongs to the Section Biocatalysis)

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4 pages, 144 KiB

Open AccessEditorial

Microbial Biocatalysis, 2nd Edition

by Tao Pan and Zhilong Wang

Catalysts 2025, 15(6), 573; https://doi.org/10.3390/catal15060573 (registering DOI) - 9 Jun 2025

Abstract

Biocatalysis, leveraging the catalytic power of enzymes or whole microbial cells, has firmly established itself as a pivotal technology for sustainable chemical synthesis, environmental remediation, and the production of value-added compounds [...] Full article

(This article belongs to the Special Issue Microbial Biocatalysis, 2nd Edition)

21 pages, 5110 KiB

Open AccessArticle

Effect of Copper Modification on Charge Carrier Transport and Defect Properties in Carbon-Doped TiO₂ Nanotubes

by Ekaterina V. Kytina, Elizaveta A. Konstantinova, Mikhail N. Martyshov, Timofey P. Savchuk, Vladimir B. Zaitsev, Alexander I. Kokorin, Alexander S. Ilin and German V. Trusov

Catalysts 2025, 15(6), 572; https://doi.org/10.3390/catal15060572 - 9 Jun 2025

Abstract

For the efficient operation of various TiO₂-based devices, it is important to understand the patterns of electric charge transport. In the present paper TiO₂-C-Cu nanocomposites were synthesized by the electrochemical method. The band gap energy Eg of all systems [...] Read more.

For the efficient operation of various TiO₂-based devices, it is important to understand the patterns of electric charge transport. In the present paper TiO₂-C-Cu nanocomposites were synthesized by the electrochemical method. The band gap energy Eg of all systems was found to be approximately the same, 3.2 eV. Both copper ions replacing titanium ions and copper ions within the CuO phase were detected. The modification of TiO₂-C nanotubes by copper led to a significant increase in conductivity and photocurrent, which may be associated with the formation of new donor states (Ti³⁺ centers) creating levels in the band gap of TiO₂-C-Cu. The characteristics of charge carrier transport (including photocurrent) in TiO₂-C-Cu materials were revealed for the first time. The conductivity at DC and at low frequencies of AC is due to the movement of electrons along the conduction zone, whereas at high frequencies there is a hopping mechanism of conduction. The acquired original results testify to the potential usage of TiO₂-C-Cu nanocomposites in the field of catalysis and photoelectrochemistry. Full article

(This article belongs to the Special Issue Catalysts and Photocatalysts Based on Mixed Metal Oxides)

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33 pages, 2401 KiB

Open AccessReview

Recent Advances in Enzyme Immobilization: The Role of Artificial Intelligence, Novel Nanomaterials, and Dynamic Carrier Systems

by Melesse Tadesse and Yun Liu

Catalysts 2025, 15(6), 571; https://doi.org/10.3390/catal15060571 - 9 Jun 2025

Abstract

Enzymes, as nature’s precision biocatalysts, hold transformative potential across industrial, environmental, and biomedical sectors. However, their instability, solvent sensitivity, and limited reusability in their free form necessitate advanced immobilization strategies to enhance their robustness and scalability. This review critically examines cutting-edge advancements in [...] Read more.

Enzymes, as nature’s precision biocatalysts, hold transformative potential across industrial, environmental, and biomedical sectors. However, their instability, solvent sensitivity, and limited reusability in their free form necessitate advanced immobilization strategies to enhance their robustness and scalability. This review critically examines cutting-edge advancements in enzyme immobilization, focusing on the integration of artificial intelligence (AI), novel nanomaterials, and dynamic carrier systems to overcome the traditional limitations of mass transfer, enzyme leakage, and cost inefficiency. Key innovations such as metal–organic frameworks (MOFs), magnetic nanoparticles, self-healing hydrogels, and 3D-printed scaffolds are highlighted for their ability to optimize enzyme orientation, stability, and catalytic efficiency under extreme conditions. Moreover, AI-driven predictive modeling and machine learning emerge as pivotal tools for rationalizing nanomaterial synthesis, multi-enzyme cascade design, and toxicity assessment, while microfluidic systems enable precise biocatalyst fabrication. This review also explores emerging carrier-free strategies, including cross-linked enzyme aggregates (CLEAs) and DNA-directed immobilization, which minimize diffusion barriers and enhance substrate affinity. Despite progress, challenges persist in regards to eco-friendly nanomaterial production, industrial scalability, and real-world application viability. Future directions emphasize sustainable hybrid material design, AI-aided lifecycle assessments, and interdisciplinary synergies between synthetic biology, nanotechnology, and data analytics. By connecting laboratory innovation with industrial needs, this work provides a forward-thinking framework to harness immobilized enzymes for achieving global sustainability goals, particularly in bioremediation, bioenergy, and precision medicine. Full article

(This article belongs to the Section Biocatalysis)

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16 pages, 5609 KiB

Open AccessReview

Research Progress in the Remediation of Arsenic- and Cadmium-Contaminated Groundwater Mediated by Iron and Manganese Biomineralization

by Feixing Li, Jixiang Cai, Xinxin Zhao, Hui Liu, Fanfan Ju and Youwen Li

Catalysts 2025, 15(6), 570; https://doi.org/10.3390/catal15060570 - 9 Jun 2025

Abstract

Arsenic (As) and cadmium (Cd) contamination in groundwater poses significant risks to human health and environmental sustainability. Iron–manganese minerals and associated microorganisms in subsurface environments exhibit remarkable potential for immobilizing and transforming toxic metal(loid)s through adsorption, redox reactions, and co-precipitation. This study integrates [...] Read more.

Arsenic (As) and cadmium (Cd) contamination in groundwater poses significant risks to human health and environmental sustainability. Iron–manganese minerals and associated microorganisms in subsurface environments exhibit remarkable potential for immobilizing and transforming toxic metal(loid)s through adsorption, redox reactions, and co-precipitation. This study integrates bibliometric analysis with mechanistic review strategies to systematically evaluate the roles of iron–manganese biomineralization in As/Cd stabilization. Bibliometric insights identify emerging research trends, including the application of biogenic oxides and microbial redox cycles in groundwater remediation. Mechanistic analysis reveals how microbial–mineral interactions regulate As/Cd sequestration, emphasizing the influence of environmental factors such as pH, redox conditions, and microbial metabolic pathways. Case studies demonstrate the viability of in situ remediation technologies leveraging these biogeochemical processes, though challenges persist in achieving consistent field-scale performance and long-term stability. Future efforts should prioritize optimizing microbial consortia, advancing real-time monitoring systems, and integrating biogeochemical strategies with engineered barriers. By synthesizing quantitative trends and mechanistic principles, this work provides actionable frameworks for enhancing natural attenuation and designing sustainable remediation systems for metal-contaminated groundwater. Full article

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25 pages, 3547 KiB

Open AccessReview

Advances in Half-Sandwich Rare-Earth Catalysts for Conjugated Dienes Polymerization

by Di Kang, Rongqing Ma, Hongfan Hu, Yi Zhou, Guoliang Mao and Shixuan Xin

Catalysts 2025, 15(6), 569; https://doi.org/10.3390/catal15060569 - 9 Jun 2025

Abstract

Polybutadiene (PB) and polyisoprene (PI) rubbers are indispensable synthetic elastomeric materials widely used in tires, footwear, hose, belts, sealants, electricity, construction, and other applications. Nowadays, PB and PI elastomers are produced from butadiene (BD) and isoprene (IP) monomers via transition-metal-mediated coordination polymerization. Transition [...] Read more.

Polybutadiene (PB) and polyisoprene (PI) rubbers are indispensable synthetic elastomeric materials widely used in tires, footwear, hose, belts, sealants, electricity, construction, and other applications. Nowadays, PB and PI elastomers are produced from butadiene (BD) and isoprene (IP) monomers via transition-metal-mediated coordination polymerization. Transition metal catalytic systems consist of a precise characteristic structural unit at the molecular level: well known as “single-site catalysts” (SSCs). These have experienced a revolutionary advance in the recently developed conjugated dienes synthetic rubber method. Among the SSCs, a class of rare-earth, metal-centered half-sandwich molecule has been identified as a high-performance catalytic system for conjugated dienes polymerization. These novel half-sandwich rare-earth (HSRE) catalytic systems exhibit several irreplaceable advantages compared with the conventional Ziegler–Natta-type catalytic systems. These HSRE catalytic systems can create novel conjugated diene rubbers (CDRs) with high catalytic reactivity, high stereoselectivity, an adjustable polymer chain microstructure, and high molecular weights and are considered to be the next generation of ecofriendly and economic catalytic systems for industrial applications. This paper delivers a concise review of some important synthetic methods for representative HSRE complexes with characteristic structures and of the utilization of some HSRE catalytic systems for the preparation of high-performance CDRs, especially highly stereoregular PI and PB materials. Full article

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

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24 pages, 3128 KiB

Open AccessReview

Biochar-Based Materials for Catalytic CO₂ Valorization

by Shahab Zomorodbakhsh, Lucas D. Dias, Mário J. F. Calvete, Andreia F. Peixoto, Rui M. B. Carrilho and Mariette M. Pereira

Catalysts 2025, 15(6), 568; https://doi.org/10.3390/catal15060568 - 8 Jun 2025

Abstract

Biochar-based materials have gathered increasing attention as sustainable catalysts for carbon dioxide (CO₂) valorization, offering a green alternative to traditional metal-based systems. Produced from renewable biomass through pyrolysis, biochar possesses key features—such as high surface area, rich porosity and tunable surface [...] Read more.

Biochar-based materials have gathered increasing attention as sustainable catalysts for carbon dioxide (CO₂) valorization, offering a green alternative to traditional metal-based systems. Produced from renewable biomass through pyrolysis, biochar possesses key features—such as high surface area, rich porosity and tunable surface chemistry—that make it particularly suited for heterogeneous catalysis. This review highlights recent advances in the use of biochar-derived catalysts for key CO₂ conversion reactions, focusing on cycloaddition to epoxides, dry reforming of methane and catalytic biomass upgrading. Emphasis is given to the role of biochar’s origin and preparation methods, which critically influence its structure, surface functionality and catalytic performance. Feedstocks rich in mineral content or oxygenated groups, for instance, can enhance CO₂ activation and product selectivity. Furthermore, tailored modifications—such as doping with heteroatoms or supporting metal nanoparticles—further boost catalytic activity and stability by tuning acid–base behavior, while maintaining low toxicity and cost-effectiveness. Compared to conventional catalysts, biochar-based systems offer advantages in low cost, recyclability and resistance to deactivation. Challenges remain in standardizing production methods, controlling structural variability, minimizing metal leaching and scaling up. This review presents biochar as a versatile, renewable platform for CO₂ utilization, highlighting the importance of rational design, feedstock selection and functionalization strategies for developing efficient, sustainable catalytic systems, in line with green chemistry and circular economy principles. Full article

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

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17 pages, 4448 KiB

Open AccessArticle

Design of Bimetallic Active Sites via Transition Metal Doping JANUS In₂S₂X for Highly Selective Photocatalytic CO₂ Reduction

by Yuhua Chi, Zhengnan Chen, Mengxin Ji, Wei Cai, Hao Ren, Wen Zhao and Wenyue Guo

Catalysts 2025, 15(6), 567; https://doi.org/10.3390/catal15060567 - 8 Jun 2025

Abstract

A rational design strategy for active sites on the catalyst surface can effectively enhance CO₂ reduction reaction (CO₂RR) selectivity. Transition metal atoms from the fourth (Sc–Ni) and fifth (Y–Mo, Ru–Pd) periods were doped onto the In₂S₂X [...] Read more.

A rational design strategy for active sites on the catalyst surface can effectively enhance CO₂ reduction reaction (CO₂RR) selectivity. Transition metal atoms from the fourth (Sc–Ni) and fifth (Y–Mo, Ru–Pd) periods were doped onto the In₂S₂X (X = Se, Te) surface to control bimetallic active sites. The study showed that the d-band center’s position of the dopant atom significantly influences CO₂RR selectivity. Cations with positive d-band centers further from the Fermi level are more inclined towards CH₂O, while those with negative d-band centers closer to the Fermi level favor HCOOH; cations with d-band centers near the Fermi level exhibit a strong preference for CH₃OH. This study systematically elucidates the intrinsic mechanisms and offers a significant theoretical foundation for developing highly selective photocatalysts. Full article

(This article belongs to the Special Issue Modeling and Simulation of Next-Generation Catalytic Materials for Energy and Environment Applications)

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20 pages, 5663 KiB

Open AccessArticle

Facile and Low-Cost Fabrication of ZnO/Kaolinite Composites by Modifying the Kaolinite Composition for Efficient Degradation of Methylene Blue Under Sunlight Illumination

by Humera Shaikh, Ramsha Saleem, Imran Ali Halepoto, Muhammad Saajan Barhaam, Muhammad Yousuf Soomro, Mazhar Ali Abbasi, Nek Muhammad Shaikh, Muhammad Ali Bhatti, Shoukat Hussain Wassan, Elmuez Dawi, Aneela Tahira, Matteo Tonezzer and Zafar Hussain Ibupoto

Catalysts 2025, 15(6), 566; https://doi.org/10.3390/catal15060566 - 6 Jun 2025

Abstract

Zinc oxide (ZnO) photocatalysts are recognized for their ease of synthesis, cost-effectiveness, efficiency, scalability, and environmental compatibility, making them highly suitable for addressing wastewater contamination. In this study, various compositions of kaolinite were used for the hydrothermal deposition of ZnO, including 0.5%, 0.75%, [...] Read more.

Zinc oxide (ZnO) photocatalysts are recognized for their ease of synthesis, cost-effectiveness, efficiency, scalability, and environmental compatibility, making them highly suitable for addressing wastewater contamination. In this study, various compositions of kaolinite were used for the hydrothermal deposition of ZnO, including 0.5%, 0.75%, 1%, and 1.25%. The main purpose of this study was to evaluate the effect of kaolinite toward the enhanced performance of ZnO through modification of particle size, morphology and surface functional groups. Several analytical techniques were employed to obtain structural and optical results, including scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and UV–visible spectroscopy, revealing significant changes in particle shape, particle size, surface functional groups, and optical band gap when kaolinite was added. The ZnO/kaolinite composite (sample 4) with 1.25% kaolinite content demonstrated outstanding photocatalytic performance for the degradation of methylene blue in natural sunlight. For sample 4, 15 mg of the dye in a 3.4 × 10⁻⁵ M dye solution exhibited a degradation efficiency of 99%. In contrast, when using 15 mg of catalyst dose and 1.5 × 10⁻⁵ M dye solution, the degradation efficiency was observed to be almost 100%, thus indicating that catalyst dose and dye concentration affect degradation efficiency. The reusability test revealed that sample 4 retained degradation efficiency of 98% after five cycles without showing any morphological changes. By decorating ZnO with kaolinite mineral clay, this study provides exciting findings and insights into the development of low-cost photocatalysts, which could be used to produce solar-powered hydrogen and treat wastewater. Full article

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31 pages, 5246 KiB

Open AccessReview

Recent Advances in PDI-Based Heterojunction Photocatalysts for the Degradation of Organic Pollutants and Environmental Remediation

by Xiaofang Song, Jiahui Lou, Yaqiong Huang and Yijiang Chen

Catalysts 2025, 15(6), 565; https://doi.org/10.3390/catal15060565 - 6 Jun 2025

Abstract

With the rapid advancement of industrialization, the adverse impacts of organic pollutants on the water environment of aquatic ecosystems have become increasingly concerning. Consequently, the development of efficient and environmentally friendly photocatalytic degradation technologies has attracted considerable research attention. Perylene diimide (PDI)-based heterojunction [...] Read more.

With the rapid advancement of industrialization, the adverse impacts of organic pollutants on the water environment of aquatic ecosystems have become increasingly concerning. Consequently, the development of efficient and environmentally friendly photocatalytic degradation technologies has attracted considerable research attention. Perylene diimide (PDI)-based heterojunction photocatalysts have demonstrated remarkable potential in degrading organic pollutants, attributed to their broad spectral response, high charge separation efficiency, and exceptional stability. In recent years, substantial progress has been achieved in the field of PDI-based heterojunction photocatalysts. This paper provides an in-depth review of the existing research on PDI-based heterojunction photocatalysts. Specifically, it elucidates the principles and types of heterojunction construction, as well as the design and synthesis strategies for PDI-based heterojunction photocatalysts. Furthermore, this paper provides a comprehensive summary of the latest advancements in performance optimization and catalytic mechanisms. Finally, the existing challenges and future prospects of PDI-based heterojunction photocatalytic materials are discussed, with the aim of offering innovative solutions for the purification of resource-oriented wastewater. Full article

(This article belongs to the Topic Advanced Composites for Waste Valorization and Pollutant Degradation)

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15 pages, 4266 KiB

Open AccessArticle

Co-Catalyst-Free Al₆Si₂O₁₃/Cd_8.05Zn_1.95S₁₀ Nanocomposites for Visible-Light-Driven Stable H₂ Evolution and DDVP Degradation

by Zhenhua Li, Aoyun Meng, Wen Li, Guoyuan Xiong, Mingfu Ye, Yaqiang Meng and Zhen Li

Catalysts 2025, 15(6), 564; https://doi.org/10.3390/catal15060564 - 5 Jun 2025

Abstract

The design of efficient and stable visible-light-driven photocatalysts is paramount for sustainable hydrogen (H₂) evolution and the degradation of organophosphorus pesticides, exemplified by dichlorvos (DDVP). In this work, we synthesized a co-catalyst-free nanocomposite photocatalyst composed of Al₆Si₂O [...] Read more.

The design of efficient and stable visible-light-driven photocatalysts is paramount for sustainable hydrogen (H₂) evolution and the degradation of organophosphorus pesticides, exemplified by dichlorvos (DDVP). In this work, we synthesized a co-catalyst-free nanocomposite photocatalyst composed of Al₆Si₂O₁₃ (ASO) and Cd_8.05Zn_1.95S₁₀ (ZCS). By constructing a Type-I heterojunction, the optimized ASO/ZCS-1 nanocomposite (ASO loading ratio: 30%) enhanced visible-light-driven H₂ evolution activity (5.1 mmol g⁻¹ h⁻¹), nearly doubling that of pristine ZCS (2.7 mmol g⁻¹ h⁻¹). Stability assessments revealed catalytic durability for ASO/ZCS-1 over five successive cycles, whereas the activity of pure ZCS precipitously declined to 59.7% of its initial level. Additionally, ASO, ZCS, and ASO/ZCS-2 (ASO loading ratio: 50%) demonstrated notable photocatalytic efficiency toward DDVP degradation without any co-catalyst, reducing DDVP concentration to 56.2% (ASO), 18.9% (ASO/ZCS-2), and 38.4% (ZCS), with corresponding degradation stability of 93.8%, 95.1%, and 93.8%, respectively. These results underscore the superior photocatalytic activity and stability of ASO, ZCS, and ASO/ZCS in the remediation of organophosphorus pesticides, with the Type-I heterojunction structure of ASO/ZCS enhancing both degradation activity and stability. Comprehensive characterizations by X-ray photoelectron spectroscopy (XPS), ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), and differential charge density analyses verified the Type-I heterojunction charge-transfer mechanism, effectively suppressing charge recombination and thus improving photocatalytic performance. Consequently, ASO/ZCS nanocomposites exhibit significant promise for broad applications in sustainable H₂ production, pollutant degradation, and ensuring food and agricultural product safety. Full article

(This article belongs to the Special Issue Recent Developments in Photocatalytic Hydrogen Production)

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17 pages, 3660 KiB

Open AccessArticle

Improving the Thermal Stability of Xylanase XynASP from Aspergillus Saccharolyticus JOP 1030-1 Through Modular Assembly

by Jinjin Zhu, Qing Zhang, Jiaxin Zhao, Xueting Fu, Mingzhu Wang, Yan Liu, Hui Wang, Hongli Xi and Tongbiao Li

Catalysts 2025, 15(6), 563; https://doi.org/10.3390/catal15060563 - 5 Jun 2025

Abstract

Xylanases, important enzymes in the food industry, have severely limited use in industrial applications due to insufficient thermal stability. This study focused on improving the thermostability of XynASP, a glycoside hydrolase family 11 (GH11) xylanase from Aspergillus saccharolyticus JOP 1030-1, through modular assembly [...] Read more.

Xylanases, important enzymes in the food industry, have severely limited use in industrial applications due to insufficient thermal stability. This study focused on improving the thermostability of XynASP, a glycoside hydrolase family 11 (GH11) xylanase from Aspergillus saccharolyticus JOP 1030-1, through modular assembly and rational mutagenesis. By aligning XynASP with nine thermostable GH11 homologs, six variable structural modules (β1, β3, β6, β7, α1, β14) and eight non-conserved residues were identified. Six chimeras (Z1, Z2, Z3, Z4, Z5, Z6) and eight single mutants (S131T, Y133T, A137G, A144T, T147Y, A156R, V198M, and Y204Q) were constructed. Among these, the β3-module-substituted chimera Z2 exhibited a 15.4-fold extended half-life at 45 °C compared to wild-type XynASP. Single-point mutagenesis revealed that V198M showed the highest residual activity after thermal treatment. To further optimize stability, combinatorial mutagenesis was performed: the double mutant A144T/V198M demonstrated a 4.3-fold longer half-life at 50 °C. Combining Z2 with the A144T/V198M mutations yielded the chimeric ZM, which demonstrated a 26.5-fold increase in half-life at 50 °C and a 5.5-fold improvement in catalytic efficiency (197.4 U/mg) compared to wild-type XynASP. Structural analysis and molecular dynamics simulations showed that increased hydrophobic interactions at both the N- and C-termini improved the structural stability of chimeric ZM, while increasing the flexibility of the thumb can offset the negative impact on catalytic activity during thermal stability modification of GH11 xylanase. This study further confirmed that modular assembly is an effective approach for obtaining high-activity, heat-resistant xylanases. This study also notably deepened our understanding of the thermal stability mechanisms of xylanases. Full article

(This article belongs to the Section Biocatalysis)

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22 pages, 5374 KiB

Open AccessFeature PaperReview

The Construction and Photocatalytic Application of Covalent Triazine Framework (CTF)-Based Composites: A Brief Review

by Yuchen Wei, Quanmei Zhou, Xinglin Wang, Yifan Liao, Jiayi Meng, Yamei Huang, Linlin Gao and Weilin Dai

Catalysts 2025, 15(6), 562; https://doi.org/10.3390/catal15060562 - 5 Jun 2025

Abstract

Covalent triazine frameworks (CTFs) are a class of porous organic semiconductors containing a large number of triazine units, which gives them many properties suitable for photocatalysis, such as high porosity, good tunability, and excellent chemical stability. However, it is difficult to achieve high [...] Read more.

Covalent triazine frameworks (CTFs) are a class of porous organic semiconductors containing a large number of triazine units, which gives them many properties suitable for photocatalysis, such as high porosity, good tunability, and excellent chemical stability. However, it is difficult to achieve high activity, stability, and selectivity at the same time using a single CTF in a specific catalytic reaction. Therefore, it is necessary to find ways to combine CTFs with other materials to improve their photocatalysis activity. From this perspective, some construction methods and the latest progress of CTF-based composites are presented, and their applications in the field of photocatalysis are introduced. Finally, the future of CTF materials in catalytic applications is proposed, which provides some insights into the research and exploration of CTF-based composites. Full article

(This article belongs to the Section Photocatalysis)

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23 pages, 1513 KiB

Open AccessArticle

A New Serine Protease (AsKSP) with Fibrinolytic Potential Obtained from Aspergillus tamarii Kita UCP 1279: Biochemical, Cytotoxic and Hematological Evaluation

by José P. Martins Barbosa-Filho, Renata V. Silva Sobral, Viviane N. S. Alencar, Marllyn Marques Silva, Juanize M. Silva Batista, Galba Maria Campos-Takaki, Wendell W. C. Albuquerque, Romero M. P. Brandão-Costa, Ana Lúcia Figueiredo Porto, Ana C. L. Leite and Thiago Pajéu Nascimento

Catalysts 2025, 15(6), 561; https://doi.org/10.3390/catal15060561 - 5 Jun 2025

Abstract

This study aimed to characterize and evaluate the fibrinolytic, thrombolytic, hematological, and toxicological aspects of a serine protease (AsKSP) from Aspergillus tamarii Kita UCP 1279. The enzyme was purified using a two-phase aqueous system and assessed for optimal pH (7.0) and temperature (50 °C), [...] Read more.

This study aimed to characterize and evaluate the fibrinolytic, thrombolytic, hematological, and toxicological aspects of a serine protease (AsKSP) from Aspergillus tamarii Kita UCP 1279. The enzyme was purified using a two-phase aqueous system and assessed for optimal pH (7.0) and temperature (50 °C), stability, and effects of metal ions, inhibitors, and surfactants. AsKSP exhibited stability for up to 120 min at 50 °C and 36 h at pH 7.0. Enzymatic activity was enhanced by Na⁺ and Zn²⁺ and non-ionic surfactants (Tween-80) but inhibited by Cu²⁺, Fe³⁺, Triton X-100, and SDS, reducing activity by up to 62.35%. The highest amidolytic activity was observed for the substrate N-succinyl-Gly–Gly–Phe-p-nitroanilide. SDS-PAGE analysis indicated an approximate molecular mass of 90 kDa. The enzyme showed fibrinolytic activity, degrading 38.81% of fibrin clots in vitro after 90 min, without affecting fibrinogen. Cytotoxicity assays indicated no toxicity (cell viability > 80%). Coagulation assays showed slight prolongation of prothrombin time (PT) and activated partial thromboplastin time (aPTT), with no effect on thrombin time. No red blood cell lysis was observed, and albumin increased enzymatic activity by 31.70%. These findings demonstrate that Aspergillus tamarii Kita UCP 1279 produces a fibrinolytic protease with potential for thrombus treatment, providing a promising foundation for drug development. Full article

(This article belongs to the Section Catalysis for Pharmaceuticals)

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