Catalysts

21 pages, 3097 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)

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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24 pages, 3631 KiB

Open AccessReview

A Review on Production of Ethylene Oxide from Epoxidation of Ethylene: Catalysis, Mechanism and Kinetics

by Mahammad Ali Saritala, Mohammed Muzammil, Mohammad R. Quddus, Shaikh Abdur Razzak and Mohammad M. Hossain

Catalysts 2025, 15(6), 560; https://doi.org/10.3390/catal15060560 - 4 Jun 2025

Abstract

This review describes the different developments in the production of ethylene oxide (EO) by epoxidation of ethylene. EO is an important chemical intermediate for the manufacture of a variety of industrial and consumer products, such as ethylene glycol, plastics, and pharmaceuticals. The conventional [...] Read more.

This review describes the different developments in the production of ethylene oxide (EO) by epoxidation of ethylene. EO is an important chemical intermediate for the manufacture of a variety of industrial and consumer products, such as ethylene glycol, plastics, and pharmaceuticals. The conventional gas-phase epoxidation process using silver-based catalysts suffers from major drawbacks, including low selectivity and high carbon dioxide emissions. This review underlines emerging solutions for efficiency and sustainability improvement in EO production. Major developments in catalyst design, including novel silver-based hybrid nanostructures, Mn-N₄GP catalysts, and chemical looping epoxidation processes, are presented. It also discusses developments in reaction kinetics, including catalyst surface optimization and the use of dopants. The article also outlines catalyst deactivation challenges, cost, and scalability and describes future research directions on renewable feedstocks, reducing energy consumption and most importantly environmental impact. These innovations are oriented toward a more sustainable and economical route for large-scale manufacturing of ethylene oxide. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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21 pages, 7386 KiB

Open AccessFeature PaperArticle

Enhanced Stability and Activity of Nitrogen-Doped Carbon Nanotube-Supported Ni Catalysts for Methane Dry Reforming

by Zhizhi Tao, Dong Shen, Yanni Liu, Xiaodi Zhang and Guojie Zhang

Catalysts 2025, 15(6), 559; https://doi.org/10.3390/catal15060559 - 4 Jun 2025

Abstract

The dry reforming of methane (DRM) converts two greenhouse gases, CH₄ and CO₂, into H₂ and CO, offering a crucial technological pathway for reducing greenhouse gas emissions and producing clean energy. However, the reaction faces two main challenges: high [...] Read more.

The dry reforming of methane (DRM) converts two greenhouse gases, CH₄ and CO₂, into H₂ and CO, offering a crucial technological pathway for reducing greenhouse gas emissions and producing clean energy. However, the reaction faces two main challenges: high activation energy barriers require high temperatures to drive the reaction, while sintering and carbon deactivation at high temperatures are common with conventional nickel-based catalysts, which severely limit the further development of the methane dry reforming reaction. In this study, a nitrogen-doped carbon nanotube-loaded nickel catalytic system (Ni/NCNT) was developed to overcome the challenges caused by limited active sites while maintaining the stable structure of the Ni/CNT system. Ni/NCNT catalysts were prepared using different nitrogen precursors, and the impact of the mixing method on catalytic performance was examined. Characterization using H₂-TPR, XPS, and TEM revealed that nitrogen doping enhanced the metal–support interaction (MSI). Additionally, pyridine nitrogen species synergistically interact with nickel particles, modulating the electronic environment on the carbon nanotube surface and increasing catalyst active site density. The Ni/NCNT-IU catalyst, prepared with impregnated urea, exhibited excellent stability, with methane conversion decreasing from 85.0% to 82.9% over 24 h of continuous reaction. This study supports the use of non-precious-metal carbon-based catalysts in high-temperature catalytic systems, which is strategically important for the industrialization of DRM and the development of decarbonized energy conversion. Full article

(This article belongs to the Special Issue Catalysis for Hydrogen Storage and Release)

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14 pages, 3371 KiB

Open AccessArticle

Nitrogen-Defect-Driven PtCu Dual-Atom Catalyst for Photocatalytic CO₂ Reduction

by Xin He, Ting Liu, Hao Wang and Yongming Luo

Catalysts 2025, 15(6), 558; https://doi.org/10.3390/catal15060558 - 4 Jun 2025

Abstract

Owing to global energy demands and climate change resulting from fossil fuel use, technologies capable of converting greenhouse gases into renewable energy resources are needed. One such technology is photocatalytic CO₂ reduction, which utilises solar energy to transform CO₂ into value-added [...] Read more.

Owing to global energy demands and climate change resulting from fossil fuel use, technologies capable of converting greenhouse gases into renewable energy resources are needed. One such technology is photocatalytic CO₂ reduction, which utilises solar energy to transform CO₂ into value-added hydrocarbons. However, the application of photocatalytic CO₂ reduction is limited by the inefficiency of existing photocatalysts. In this study, we developed a nitrogen-deficient g-C₃N₄-confined PtCu dual-atom catalyst (PtCu/V_N-C₃N₄) for photocatalytic CO₂ reduction. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy confirmed the atomic-level anchoring of PtCu pairs onto the nitrogen-vacancy-rich g-C₃N₄ nanosheets. The optimised PtCu/V_N-C₃N₄ exhibited superior photocatalytic performance, with CO and CH₄ evolution rates of 13.3 µmol/g/h and 2.5 µmol/g/h, respectively, under visible-light irradiation. Mechanistic investigations revealed that CO₂ molecules were preferentially adsorbed onto the PtCu dual sites, initiating a stepwise reduction pathway. In situ diffuse reflectance infrared Fourier-transform spectroscopy identified the formation of a key intermediate (HCOO*), whereas interfacial wettability studies demonstrated efficient H₂O adsorption on PtCu sites, providing essential proton sources for CO₂ protonation. Photoelectrochemical characterisation further confirmed the enhanced charge-transfer kinetics in PtCu/V_N-C₃N₄, which were attributed to the synergistic interplay between the nitrogen vacancies and dual-atom sites. Notably, the dual-active-site architecture minimised the competitive adsorption between CO₂ and H₂O molecules, thereby optimising the surface reaction pathways. This study establishes a rational strategy for designing atomically precise dual-atom catalysts through defect engineering, achieving concurrent improvements in activity, selectivity, and charge carrier utilisation for solar-driven CO₂ conversion. Full article

(This article belongs to the Section Photocatalysis)

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14 pages, 1634 KiB

Open AccessArticle

Modified Fischer–Tropsch Pathway for CO₂ Hydrogenation to Aromatics: Impact of Si/Al Ratio of H-ZSM-5 Zeolite on Light Aromatics Selectivity

by Shaocong Wang, Yu Sun, Shiyuan Lin, Zhongxu Bian, Yuanyuan Han, Xinze Bi, Zhaorui Zhang, Xiaojie Liu, Dandan Liu, Yang Wang and Mingbo Wu

Catalysts 2025, 15(6), 557; https://doi.org/10.3390/catal15060557 - 4 Jun 2025

Abstract

Despite significant advancements in designing tandem catalysts for CO₂ hydrogenation to aromatics, the role of zeolite acid property in regulating the selectivity of light aromatics (benzene, toluene, and xylene, abbreviated as BTX) remains unclear. Herein, we report H-ZSM-5 zeolite (denoted as HZ-X, [...] Read more.

Despite significant advancements in designing tandem catalysts for CO₂ hydrogenation to aromatics, the role of zeolite acid property in regulating the selectivity of light aromatics (benzene, toluene, and xylene, abbreviated as BTX) remains unclear. Herein, we report H-ZSM-5 zeolite (denoted as HZ-X, where X represents the Si/Al ratio) integrated with a Na-promoted FeCo-based catalyst (NaFeCo) for CO₂ hydrogenation into aromatics via a modified Fischer–Tropsch synthesis pathway. This study systematically modulates the Si/Al ratio of acidic zeolite and examines its critical role in influencing the light aromatics selectivity. The optimized NaFeCo/HZ-50 catalyst achieves a CO₂ conversion of 43% with an aromatics selectivity of 41%, including a BTX fraction of 57% in total aromatics. Multiple characterization techniques (NH₃-TPD, Py/DTBPy-IR, ²⁷Al NMR, etc.) clarify that acidic zeolite HZ-50 exhibits appropriate acid density and lower external surface acid sites, which synergistically boost the efficient aromatics and BTX synthesis while suppressing the undesirable alkylation and isomerization reactions on the external acid sites. This work develops a highly efficient multifunctional catalyst for CO₂ hydrogenation to light aromatics, especially offering guidance for the rational design of acidic zeolite with unique shape-selective functions. Full article

(This article belongs to the Special Issue Catalysis on Zeolites and Zeolite-Like Materials, 3rd Edition)

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14 pages, 2373 KiB

Open AccessArticle

Isomeric Anthraquinone-Based Covalent Organic Frameworks for Boosting Photocatalytic Hydrogen Peroxide Generation

by Shengrong Yan, Songhu Shi, Wenhao Liu, Fang Duan, Shuanglong Lu and Mingqing Chen

Catalysts 2025, 15(6), 556; https://doi.org/10.3390/catal15060556 - 3 Jun 2025

Abstract

Utilizing isomeric monomers to construct covalent organic frameworks (COFs) could easily and precisely regulate their structure in order to raise the photocatalytic performance towards two-step single-electron oxygen reduction reaction (ORR) to hydrogen peroxide (H₂O₂). Herein, isomeric anthraquinone (AQ)-based COFs [...] Read more.

Utilizing isomeric monomers to construct covalent organic frameworks (COFs) could easily and precisely regulate their structure in order to raise the photocatalytic performance towards two-step single-electron oxygen reduction reaction (ORR) to hydrogen peroxide (H₂O₂). Herein, isomeric anthraquinone (AQ)-based COFs (designated as 1,4-DQTP and 2,6-DQTP) were successfully fabricated through a simple yet effective one-step solvothermal synthesis approach, only utilizing isomeric monomers with alterations in the catalysts. Specifically, the black 1,4-DQTP displayed a high photocatalytic H₂O₂ production rate of 865.4 µmol g⁻¹ h⁻¹, with 2.44-fold enhancement compared to 2,6-DQTP (354.7 µmol g⁻¹ h⁻¹). Through a series of experiments such as electron paramagnetic resonance (EPR) spectroscopy and the free radical quenching experiments, as well as density functional theory (DFT) calculations, the photocatalytic mechanism revealed that compared with 2,6-DQTP, 1,4-DQTP possessed a stronger and broader visible light absorption capacity, and thus generated more photogenerated e⁻-h⁺ pairs. Ultimately, more photogenerated electrons were enriched on the AQ motif via a more apparent electron push–pull effect, which provided a stable transfer channel for e⁻ and thus facilitated the generation of superoxide anion radical intermediates (•O₂⁻). On the other hand, the negative charge region of AQ’s carbonyl group evidently overlapped with that of TP, indicating that 1,4-DQTP had a higher chemical affinity for the uptake of protons, and thus afforded a more favorable hydrogen donation for H⁺. As a consequence, the rational design of COFs utilizing isomeric monomers could synergistically raise the proton-coupled electron transfer (PCET) kinetics for two-step single-electron ORR to H₂O₂ under visible light illumination. This work provides some insights for the design and fabrication of COFs through rational isomer engineering to modulate their photocatalytic activities. Full article

(This article belongs to the Special Issue Nanostructured Photocatalysts for Hydrogen Production)

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14 pages, 3080 KiB

Open AccessFeature PaperArticle

Influence of Ni Addition on Au/CeO₂ Photocatalysts for Solar Photocatalytic H₂ Production by Glycerol Photoreforming

by Eleonora La Greca, Maria Teresa Armeli Iapichino, M. Carmen Herrera Beurnio, Francisco J. Urbano Navarro, Leonarda Francesca Liotta, Salvatore Scirè and Roberto Fiorenza

Catalysts 2025, 15(6), 555; https://doi.org/10.3390/catal15060555 - 3 Jun 2025

Abstract

Solar glycerol photoreforming was investigated on Au-Ni/CeO₂ photocatalysts with an overall metal content equal to 1wt% and different Au/Ni weight ratios. The deposition of gold over ceria was performed by two different methods, deposition–precipitation and photoreduction. Deposition–precipitation was the best method to [...] Read more.

Solar glycerol photoreforming was investigated on Au-Ni/CeO₂ photocatalysts with an overall metal content equal to 1wt% and different Au/Ni weight ratios. The deposition of gold over ceria was performed by two different methods, deposition–precipitation and photoreduction. Deposition–precipitation was the best method to deposit gold on CeO₂ with the formation of small Au nanoparticles (around 4 nm). The most active sample (0.9 wt% Au-0.1 Ni wt%/CeO₂) provided a H₂ production rate of 350 µmol/gcat∙h, much higher than the corresponding monometallic samples. A higher amount of Ni led to detrimental effects in H₂ production, likely due to the covering of the gold surface active sites by Ni. On the contrary, the presence of a small amount of Ni (0.1 wt%) allowed a remarkable improvement of the Au/CeO₂ photocatalytic stability after consecutive runs of simulated solar irradiation. This finding, as well as the activation of synergistic effects, the improved charge carrier separation, and the exploitation of the localized surface plasmon resonance property of gold, led to the proposal of an alternative photocatalytic system to the most investigated TiO₂-based photocatalysts for H₂ production. The enhanced stability is promising to further foster the investigation of these photocatalysts applied to sustainable H₂ production. Full article

(This article belongs to the Collection Gold Catalysts)

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17 pages, 1924 KiB

Open AccessArticle

Conversion of Furfural as a Bio-Oil Model Compound over Calcium-Based Materials as Sacrificial Low-Cost Catalysts for Bio-Oil Upgrading

by Moritz Böhme, Peter A. Jensen, Martin Høj, Brian B. Hansen, Magnus Z. Stummann and Anker D. Jensen

Catalysts 2025, 15(6), 554; https://doi.org/10.3390/catal15060554 - 3 Jun 2025

Abstract

The stabilization and upgrading of biomass and waste-derived pyrolysis oils requires development of reliable, active and low-cost upgrading catalysts. Basic natural materials can act as such catalysts and convert reactive oxygenates present in biomass pyrolysis oils. The conversion of furfural as a model [...] Read more.

The stabilization and upgrading of biomass and waste-derived pyrolysis oils requires development of reliable, active and low-cost upgrading catalysts. Basic natural materials can act as such catalysts and convert reactive oxygenates present in biomass pyrolysis oils. The conversion of furfural as a model compound has been conducted in an autoclave reactor at 200 °C to 300 °C using different calcium-based materials. CaCO₃, Ca(OH)₂, CaO, cement raw meal (CRM) and calcined cement raw meal (cCRM) were screened for their catalytic activity and characterized using X-ray powder diffraction (XRD) and X-ray fluorescence (XRF), nitrogen physisorption, carbon dioxide temperature programmed desorption (CO₂-TPD) and thermogravimetric analysis (TGA). CaCO₃ and CRM had low basicity and showed no catalytic activity at 200 to 300 °C. Notably, 90% conversion of furfural was achieved at 200 °C using Ca(OH)₂ with products being mostly furfural di- and trimers. For the basic CaO and cCRM, a temperature of 250 °C or above caused rapid polymerization of furfural. The proposed mechanism follows the Cannizzaro reaction of furfural, catalyzed by basic sites, polymerization of furfuryl alcohol, decarboxylation of furoic acid and decarbonylation of furfural, releasing CO, CO₂ and H₂O. Calcined cement raw meal showed the most promise for application as low-cost, sacrificial, basic catalyst. Full article

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

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