Catalysts

22 pages, 2910 KB

Open AccessReview

Global Research Trends in Catalysis for Green Hydrogen Production from Wastewater: A Bibliometric Study (2010–2024)

by Motasem Y. D. Alazaiza, Al-Anoud Al-Yazeedi, Talal Al Wahaibi, Farouk Mjalli, Abdulkareem Abubakar, Mohammed Abd El Hameed and Mohammed Javeed Siddique

Catalysts 2025, 15(9), 915; https://doi.org/10.3390/catal15090915 - 22 Sep 2025

Abstract

By turning a waste stream into a clean energy source, green hydrogen generation from wastewater provides a dual solution to energy and environmental problems. This study presents a thorough bibliometric analysis of research trends in the field of green hydrogen generation from wastewater [...] Read more.

By turning a waste stream into a clean energy source, green hydrogen generation from wastewater provides a dual solution to energy and environmental problems. This study presents a thorough bibliometric analysis of research trends in the field of green hydrogen generation from wastewater between 2010 and 2024. A total of 221 publications were extracted from Scopus database, and VOSviewer (1.6.20) was used as a visualization tool to identify influential authors, institutions, collaborations, and thematic focus areas. The analysis revealed a significant increase in research output, with a peak of 122 publications in 2024, with a total of 705 citations. China had the most contributions with 60 publications, followed by India (30) and South Korea (26), indicating substantial regional involvement in Asia. Keyword co-occurrence and coauthorship network mapping revealed 779 distinct keywords grouped around key themes like electrolysis, hydrogen evolution reactions, and wastewater treatment. Significantly, this work was supported by contributions from 115 publication venues, with the International Journal of Hydrogen Energy emerging as the most active and cited source (40 articles, 539 citations). The multidisciplinary aspect of the area was highlighted by keyword co-occurrence analysis, which identified recurring themes including electrolysis, wastewater treatment, and hydrogen evolution processes. Interestingly, the most-cited study garnered 131 citations and discussed the availability of unconventional water sources for electrolysis. Although there is growing interest in the field, it is still in its initial phases, indicating a need for additional research, particularly in developing countries. This work offers a basic overview for researchers and policymakers who are focused on promoting the sustainable generation of green hydrogen from wastewater. Full article

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

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19 pages, 2656 KB

Open AccessArticle

Photocatalytic Degradation of Safranin O: Unraveling the Roles of Dissolved Gases, Environmental Matrices, and Reactive Species

by Meriem Bendjama and Oualid Hamdaoui

Catalysts 2025, 15(9), 914; https://doi.org/10.3390/catal15090914 - 22 Sep 2025

Abstract

This study investigates the impacts of the gas environment, water matrix, and reactive species on the TiO₂-mediated photocatalytic degradation of safranin O (SO), a dye commonly found in wastewater. A slurry reactor (UVA, 365 nm) was used to quantify SO oxidation [...] Read more.

This study investigates the impacts of the gas environment, water matrix, and reactive species on the TiO₂-mediated photocatalytic degradation of safranin O (SO), a dye commonly found in wastewater. A slurry reactor (UVA, 365 nm) was used to quantify SO oxidation while systematically varying the SO concentration (5–40 mg/L), the TiO₂ loading (0–3 g/L), the temperature (15–45 °C), and the pH (2–12). The dissolved gases (air, nitrogen, and argon) and matrices (deionized water, mineral water, and seawater) were also examined. Eight mechanistic probes (ascorbic acid, methanol, azide, nitrite, benzoquinone, oxalate, sucrose, and phenol) were used to identify active oxidants. UVA/TiO₂ achieved rapid decolorization in approximately 90 min at 10 mg/L of SO and 0.4 g/L of TiO₂. Decolorization rates decreased with increasing SO concentration due to active-site competition and inner-filter effects. Rates also exhibited a bell-shaped dependence on TiO₂ loading due to light scattering and aggregation at high solids concentrations. Temperature exhibited a non-monotonic profile with an optimum around 25 °C, and the pH displayed an optimum range with maximal removal occurring around pH 10 and declining at pH 12. Air saturation outperformed N₂ and Ar, indicating that O₂ is the terminal electron acceptor. Photocatalytic performance decreased in the order deionized water > mineral water > seawater, owing to bicarbonate/chloride scavenging and ionic-strength effects. Scavenger tests converged on ^•OH dominance, with measurable contributions from superoxide/hydrogen peroxide (O₂^•−/H₂O₂) and valence-band holes (h⁺); singlet oxygen (¹O₂) played a minor role. These findings underscore the critical interplay between operational and environmental factors and offer a practical framework for scaling TiO₂-based SO abatement in real waters. Full article

(This article belongs to the Special Issue Advances in Catalysis for Sustainable Energy and Environmental Remediation, 2nd Edition)

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16 pages, 1177 KB

Open AccessReview

Catalytic Hydrogenation of Carbon Dioxide to Methanol on MOF-Confined Metal Nanoparticles: A Review

by Zechen Ye, Wenxuan Xie and Hongyan Chen

Catalysts 2025, 15(9), 913; https://doi.org/10.3390/catal15090913 - 22 Sep 2025

Abstract

High energy demand due to boosted economic growth has led to heavy consumption of fossil fuels, thus causing massive emissions of carbon dioxide (CO₂) in the air. A promising solution to reduce carbon emissions is to convert CO₂ into methanol [...] Read more.

High energy demand due to boosted economic growth has led to heavy consumption of fossil fuels, thus causing massive emissions of carbon dioxide (CO₂) in the air. A promising solution to reduce carbon emissions is to convert CO₂ into methanol (CH₃OH), which requires high-performance catalysts. Metal nanoparticles have been in the spotlight due to their under-coordinated active sites. Nonetheless, conventional catalytic substrates have emerged with a decline in catalytic performance due to agglomeration of MNPs. Metal–organic frameworks (MOFs) have been acknowledged as alternative platforms to preclude aggregation of MNPs by encapsulation. This review introduces conventional heterogeneous catalysts on CO₂ hydrogenation to CH₃OH as the first endeavor, then summarizes recent progress of MNPs@MOFs on the same reaction, and, finally, points out the problems that remain unsolved. Full article

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

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21 pages, 4040 KB

Open AccessArticle

Plant Lipases as Versatile Biocatalysts: Experimental and Computational Insights into Castor Bean (Ricinus communis L.) Catalysis

by César Sánchez-Juárez, Alejandro González-Rivas, Omar Gómez-García, Teodoro Ibarra-Pérez, Hans Christian Correa-Aguado and Gloria Viviana Cerrillo-Rojas

Catalysts 2025, 15(9), 912; https://doi.org/10.3390/catal15090912 - 19 Sep 2025

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Abstract

Plant enzymes, such as those from castor bean (Ricinus communis L.), have been studied as biocatalysts for various industrial applications. In this study, a powdered enzyme extract was used to analyze the potential of lipases present in three castor bean varieties (LV1–LV3). [...] Read more.

Plant enzymes, such as those from castor bean (Ricinus communis L.), have been studied as biocatalysts for various industrial applications. In this study, a powdered enzyme extract was used to analyze the potential of lipases present in three castor bean varieties (LV1–LV3). Their hydrolytic activity was evaluated against olive and castor oil substrates (refined and non-refined) at pH 4.5 and 7.0. The results showed that LV2 had higher catalytic activity, managing to hydrolyze more than 98% of the oils in only 4.5 h of reaction. Additionally, diverse computational tools were employed to assess the behavior of OBL1 lipase. By molecular docking analysis, it was found that the binding of ricinoleic acid triacylglycerols to the catalytic site was favored at an acidic pH of 4.5 due to enhanced hydrogen bond formation. In contrast, at pH 7.0, hydrophobic interactions predominated. Molecular dynamics analyses of OBL1 showed that the enzyme–substrate complex is stable over time, providing a robust molecular explanation for the high catalytic efficiency observed in the experimental assays. This research stands out as one of the first to combine lab experiments with computational modeling to study castor bean lipases. Our integrated approach provides fresh insights into the enzyme’s versatile catalytic capabilities, underscoring its potential as a powerful and reliable tool for industrial biotechnology. Full article

(This article belongs to the Special Issue Biocatalysis—Enzymes in Industrial Applications)

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21 pages, 5523 KB

Open AccessArticle

L-Cysteine Enhanced Degradation of Chlorobenzene in Water Using Nano Zero-Valent Iron/Persulfate System

by Fengcheng Jiang, Guangyi Zhu, He Huang, Xixi Feng, Zhi Feng, Qiao Han, Fayang Guo, Tianjun Chang and Mingshi Wang

Catalysts 2025, 15(9), 911; https://doi.org/10.3390/catal15090911 - 19 Sep 2025

Viewed by 133

Abstract

Nano zero-valent iron (nZVI) particles have received much attention in environmental science and technology due to their unique electronic and chemical properties. While sulfate radical-based advanced oxidation processes (SR-AOPs) activated by nZVI show promise for mono-chlorobenzene (MCB) degradation, their efficiency is severely limited [...] Read more.

Nano zero-valent iron (nZVI) particles have received much attention in environmental science and technology due to their unique electronic and chemical properties. While sulfate radical-based advanced oxidation processes (SR-AOPs) activated by nZVI show promise for mono-chlorobenzene (MCB) degradation, their efficiency is severely limited by surface oxidation of nZVI and Fe³⁺ accumulation. This study aims to enhance the nZVI/persulfate (PS) system using L-cysteine (Cys) to achieve effective MCB removal. The work involved synthesizing nZVI via borohydride reduction, followed by comprehensive characterization and batch experiments of the Cys/nZVI/PS degradation system of MCB were carried out to evaluate the key influencing factors and analyze the reaction mechanism of Cys-enhanced MCB degradation. Under optimal conditions (0.1 g/L nZVI, 3 mM PS, 0.1 mM Cys, pH 3), 92.6% of MCB was degraded within 90 min—an 18.7% improvement compared to the Cys-free system. Acidic pH promoted Fe²⁺ release and significantly enhanced degradation, while HCO₃⁻ strongly inhibited the process. Mechanistic studies revealed that sulfate radicals (SO₄^•−) played a dominant role, and Cys served as an electron shuttle that facilitated the Fe³⁺/Fe²⁺ cycle and enhanced Fe⁰ conversion, thereby sustaining PS activation. This study demonstrates that Cys effectively mitigates the limitations of nZVI/PS systems and provides valuable insights for implementing efficient SR-AOPs in treating chlorinated organic contaminants. Full article

(This article belongs to the Special Issue Novel Advanced Oxidation Processes for Catalytic Degradation of Emerging Contaminants)

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12 pages, 1655 KB

Open AccessFeature PaperArticle

Two-Dimensional Multilayered Ferroelectric with Polarization-Boosted Photocatalytic Hydrogen Evolution

by Yu Peng, Liangyao Li, Yilin Xu, Xing Wang and Yu Hou

Catalysts 2025, 15(9), 910; https://doi.org/10.3390/catal15090910 - 18 Sep 2025

Viewed by 122

Abstract

Ferroelectric materials have attracted great attention for photocatalytic hydrogen (H₂) evolution due to their internal depolarization fields that promote carrier separation and directional migration. However, conventional inorganic ferroelectrics often suffer from wide band gaps and low conductivity, limiting their solar-to-hydrogen conversion [...] Read more.

Ferroelectric materials have attracted great attention for photocatalytic hydrogen (H₂) evolution due to their internal depolarization fields that promote carrier separation and directional migration. However, conventional inorganic ferroelectrics often suffer from wide band gaps and low conductivity, limiting their solar-to-hydrogen conversion efficiency. Here, we report a two-dimensional (2D) multilayered perovskite ferroelectric, [butylammonium]₂[ethylammonium]₂Pb₃I₁₀ (BAPI), which integrates robust spontaneous polarization (P_s) and excellent semiconductor properties to enable efficient photocatalysis. Under simultaneous light and ultrasonic excitation, BAPI/Pt (1 wt%) achieves a H₂ evolution rate of 1256 μmol g⁻¹ h⁻¹, which is twice that under light alone, due to dynamic polarization modulation that mitigates ionic screening and enhances internal electric fields. Notably, this enhancement vanishes when BAPI transitions to a centrosymmetric, nonpolar phase at 323 K, confirming the critical role of P_s. These findings offer a new pathway toward high-performance ferroelectric photocatalysts for solar hydrogen production. Full article

(This article belongs to the Section Photocatalysis)

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22 pages, 8198 KB

Open AccessFeature PaperArticle

Thermally Exfoliated g-C₃N_4/Ti₃C₂T_x MXene Schottky Junctions as Photocatalysts for the Removal of Valsartan from Aquatic Environments

by Christos Lykos and Ioannis Konstantinou

Catalysts 2025, 15(9), 909; https://doi.org/10.3390/catal15090909 - 18 Sep 2025

Viewed by 126

Abstract

In recent years, graphitic carbon nitride (g-C₃N₄) has gained considerable ground in the field of heterogeneous photocatalysis for the abatement of emerging contaminants from aqueous environments. Nonetheless, certain limitations, including a small surface area and a high recombination rate, [...] Read more.

In recent years, graphitic carbon nitride (g-C₃N₄) has gained considerable ground in the field of heterogeneous photocatalysis for the abatement of emerging contaminants from aqueous environments. Nonetheless, certain limitations, including a small surface area and a high recombination rate, limit its photocatalytic efficacy. In this study, g-C₃N₄ was synthesized from urea and then underwent thermal exfoliation. A portion of the exfoliated material was subsequently subjected to protonation via acid treatment, and both protonated and non-protonated variants of exfoliated g-C₃N₄ were combined with small amounts of Ti₃C₂T_x MXene. The morphology, chemical structure, and optical properties of the synthesized materials were examined using various characterization techniques. Additionally, their photocatalytic performance was evaluated through laboratory tests using the commonly detected anti-hypertensive drug valsartan as a model pollutant. The degradation kinetics of valsartan revealed that combining 1% Ti₃C₂T_x MXene with exfoliated g-C₃N₄ (both protonated and non-protonated) achieves optimal removal. Notably, the composite material 1%-pCNMX (protonated variant) displayed a 20% higher removal kinetic rate than unmodified exfoliated g-C₃N₄, removing a higher quantity of valsartan within the same time frame. Furthermore, all protonated composites proved more effective in degrading valsartan than their non-protonated counterparts, demonstrating the positive impact of acid treatment. The improved photocatalytic activity was attributed to the successful formation of Schottky junctions between g-C₃N₄ and Ti₃C₂T_x, which reduced the recombination rate of photogenerated charge carriers. Full article

(This article belongs to the Special Issue MXenes-Based Composites and Their Applications in Photocatalysis, Electrocatalysis and Thermocatalysis)

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22 pages, 6079 KB

Open AccessArticle

Response Surface Modeling and Photocatalytic Assessment of CoV₂O₆ for the Treatment of Organic Dyes

by Mohamed El Ouardi, Véronique Madigou, Virginie Chevallier, Henrik Haspel, Amal BaQaise, Mohamed Saadi, Hassan Ait Ahsaine and Madjid Arab

Catalysts 2025, 15(9), 908; https://doi.org/10.3390/catal15090908 - 18 Sep 2025

Viewed by 187

Abstract

A cobalt vanadate (CoV₂O₆) photocatalyst was successfully synthesized and characterized for the degradation of organic dyes under visible light. Structural analysis revealed a monoclinic crystalline phase with a band gap energy of 2.13 eV, indicating strong visible light absorption. [...] Read more.

A cobalt vanadate (CoV₂O₆) photocatalyst was successfully synthesized and characterized for the degradation of organic dyes under visible light. Structural analysis revealed a monoclinic crystalline phase with a band gap energy of 2.13 eV, indicating strong visible light absorption. X-ray photoelectron spectroscopy (XPS) confirmed the presence of cobalt (Co), vanadium (V), and oxygen (O) in the material composition. Morphological investigations using SEM and TEM showed highly irregular particles with no defined geometric shape. Photocatalytic activity was evaluated using Rhodamine B (RhB) and Methyl Orange (MO) as model pollutants. Degradation efficiencies of 80% and 50% were achieved for RhB and MO, respectively, highlighting a selective performance towards the cationic dye. Radical scavenging experiments indicated that hydroxyl radicals and photogenerated holes were the dominant reactive species in RhB decomposition. The photocatalytic process was further optimized using response surface methodology (RSM), and the ANOVA analysis confirmed the significance of the quadratic model (p < 0.05). These findings demonstrate the potential of CoV₂O₆ as an efficient and selective photocatalyst for treating dye-contaminated wastewater. Full article

(This article belongs to the Section Photocatalysis)

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14 pages, 5541 KB

Open AccessArticle

Activity and Stability Enhancement of Carbonic Anhydrase Entrapped Within Biomimetic Silica by Methyl-Substituted Silanes

by Su-Chun How, Xen-Shuan Kong, Chia-Jung Hu and Chi-Yang Yu

Catalysts 2025, 15(9), 907; https://doi.org/10.3390/catal15090907 - 18 Sep 2025

Viewed by 179

Abstract

Carbonic anhydrase (CA), an enzyme that accelerates CO₂ hydration, is one of the most widely used enzymes in the aid of CO₂ sequestration. We entrapped CA from Sulfurihydrogenibium azorense (SazCA) within biomimetic silica; to enhance the activity of the entrapped enzyme, [...] Read more.

Carbonic anhydrase (CA), an enzyme that accelerates CO₂ hydration, is one of the most widely used enzymes in the aid of CO₂ sequestration. We entrapped CA from Sulfurihydrogenibium azorense (SazCA) within biomimetic silica; to enhance the activity of the entrapped enzyme, the microenvironment of the silica particles was modified by using methyltrimethoxysilane (MTMS) or dimethyldimethoxysilane (DMDMS) as part of the precursors. When 10% (mol/mol) MTMS or 20% DMDMS was added to tetramethoxysilane (TMOS), the activity of entrapped SazCA increased by almost threefold when compared with the control group without these methyl-substituted silanes. In addition, all three types of entrapped SazCA, namely, the silica formed with only TMOS, 10% MTMS in TMOS, and 20% DMDMS in TMOS, exhibited improved thermal stability and pH stability. All three types of entrapped SazCA also showed good storage stability, with at least 79% of their initial activities retained after being stored at room temperature for six weeks, while the activity of the free enzyme dropped to 14% after only two days. When all three types of entrapped SazCA were applied to carbon sequestration, the efficiency remained above 90% even after ten cycles of reuse. Full article

(This article belongs to the Section Biocatalysis)

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15 pages, 5479 KB

Open AccessFeature PaperArticle

Transfer Hydrogenation of Vanillin with Formic Acid over Graphene-Encapsulated Nitrogen-Doped Bimetallic Magnetic Pd/Fe@N/C Catalyst

by Hualiang Zuo, Yulong Lei and Jianguo Liu

Catalysts 2025, 15(9), 906; https://doi.org/10.3390/catal15090906 - 18 Sep 2025

Viewed by 119

Abstract

The improved biomass-derived aldehyde compounds represent a valuable route to the production of high-value-added fuels and chemicals. However, the majority of mature catalytic systems exhibit low hydrodeoxygenation (HDO) activity, even under harsh reaction conditions. In this study, it was observed that a Pd/Fe [...] Read more.

The improved biomass-derived aldehyde compounds represent a valuable route to the production of high-value-added fuels and chemicals. However, the majority of mature catalytic systems exhibit low hydrodeoxygenation (HDO) activity, even under harsh reaction conditions. In this study, it was observed that a Pd/Fe magnetic bimetallic catalyst, in conjunction with formic acid (FA) as a hydrogen source and nitrogen-containing carbon material as a support, exhibited remarkable catalytic performance for the conversion of phenyl aldehydes in oxygenates derived from crude lignin. In the hydrogenation of vanillin, the Pd/Fe@N/C catalyst demonstrated superior catalytic activity under mild reaction conditions of 80 °C. When ethyl acetate was used as the solvent, the product was vanillyl alcohol (VA), and when cyclohexane was employed as the solvent, the product was p-methyl guaiacol (MMP). The yields achieved were 84.5% and 92.3%, respectively. It is recommended that further exploration of the FLOW reactor system be considered at a later stage due to the magnetic and easily separable characteristics of the catalyst. The excellent mass transfer and heat transfer performance of the FLOW reactor system will further ensure that the reaction conditions are moderate and will strive to achieve normal-temperature conversion. Full article

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16 pages, 3922 KB

Open AccessArticle

Characterization of a Novel Thermostable and Alkaliphilic β-Mannanase for Gel-Breaking in Guar Gum Fracturing Fluids

by Wenzhuo Tian, Tianhua Lv, Shaojing Wang, Weilong Wang, Zhiwei Wang, Shuai Chen, Yutong Tian, Yuan Yun, Guoqiang Li and Ting Ma

Catalysts 2025, 15(9), 905; https://doi.org/10.3390/catal15090905 - 18 Sep 2025

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Abstract

The development of robust and efficient β-mannanases is key to advancing environmentally friendly industrial processes, such as guar gum fracturing fluid gel-breaking. Here, we report the identification and characterization of MG4, a novel thermotolerant and alkaliphilic β-mannanase mined from the Earth’s Microbiome database. [...] Read more.

The development of robust and efficient β-mannanases is key to advancing environmentally friendly industrial processes, such as guar gum fracturing fluid gel-breaking. Here, we report the identification and characterization of MG4, a novel thermotolerant and alkaliphilic β-mannanase mined from the Earth’s Microbiome database. The recombinant enzyme has a molecular weight of 63 kDa. MG4 displayed maximum activity at 65 °C and pH 9.0, and exhibited remarkable stability across a broad pH range (7.0–10.0). It retained over 80% of its activity after incubation at 50 °C for 1 h, and its activity was enhanced more than 40% by Mg²⁺ or Ca²⁺. Moreover, MG4 (20 mg/L) reduced the viscosity of guar gum fracturing fluid to <5 m·PaS within 30 min, outperforming ammonium persulfate (APS, 500 mg/L) which required 1 h, and produced 64.5% less insoluble residue. TEM imaging directly visualized the disruption of the guar gum polymer network by MG4, explaining its efficacy and suggesting reduced formation damage risk compared to chemical breakers. This work characterizes a highly promising biocatalyst whose thermostability, alkaliphily, efficient gel-breaking, low residue yield, and minimal formation damage potential position it as a superior, eco-friendly alternative for petroleum industry applications. Full article

(This article belongs to the Section Biocatalysis)

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20 pages, 3176 KB

Open AccessFeature PaperArticle

Photocatalytic Mineralization of Emerging Organic Contaminants Using Real and Simulated Effluents in Batch and Membrane Photoreactors

by Cristina Lavorato, Angela Severino, Pietro Argurio, Raffaele Molinari, Beatrice Russo, Alberto Figoli and Teresa Poerio

Catalysts 2025, 15(9), 904; https://doi.org/10.3390/catal15090904 - 18 Sep 2025

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Abstract

Conventional wastewater treatment plants (WWTPs) have limited efficiency in removing emerging pollutants (EPs), meaning these pollutants persist and lead to widespread ecological contamination. In this study, real effluents from a WWTP were characterized using TOC and Py-GC/MS, which indicated the presence of various [...] Read more.

Conventional wastewater treatment plants (WWTPs) have limited efficiency in removing emerging pollutants (EPs), meaning these pollutants persist and lead to widespread ecological contamination. In this study, real effluents from a WWTP were characterized using TOC and Py-GC/MS, which indicated the presence of various organic compounds that could be indicative of micro-nanoplastics (MNPs) or plastics additives. To address this challenge, we propose the use of a photocatalytic membrane reactor (PMR) as an advanced treatment system capable of achieving high degradation efficiency under mild operating conditions. Preliminary experimental tests were conducted using various commercial photocatalysts (TiO₂, WO₃, Nb₂O₅), four UV lamps, and oxidants (air, O₂) using added Gemfibrozil (GEM) as a drug model compound. Real effluent samples collected from WWTP were tested with and without pretreatment to remove coarse particles prior to photocatalysis. Mineralization was achieved in both cases, but it occurred at a higher rate for the pretreated effluent. The mineralization of GEM and EPs in real effluent was achieved within five hours under UV irradiation using titanium dioxide (TiO₂) as a low-cost photocatalyst in a PMR. The results highlight the potential of photocatalytic systems, and particularly PMRs, as a promising technology for removing recalcitrant pollutants in real effluents offering a viable solution for improved environmental protection. Full article

(This article belongs to the Special Issue 15th Anniversary of Catalysts—Recent Advances in Photocatalysis)

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19 pages, 2127 KB

Open AccessFeature PaperArticle

Study on Photocatalytic Peroxone Process for Treating Organic Pollutants in Leachate Based on Modified Carbon Quantum Dots

by Shuo Wu, Nuo Meng, Lin Ma, Xiguo Zhang, Shihu Ding and Wei Wang

Catalysts 2025, 15(9), 903; https://doi.org/10.3390/catal15090903 - 18 Sep 2025

Viewed by 195

Abstract

This study couples a carbon quantum dot photocatalyst with a proton relay installed (EDTA-CQDs) for efficient hydrogen peroxide (H₂O₂) production with an ozone (O₃) system. In situ activation of O₃ is achieved by the photogenerated H [...] Read more.

This study couples a carbon quantum dot photocatalyst with a proton relay installed (EDTA-CQDs) for efficient hydrogen peroxide (H₂O₂) production with an ozone (O₃) system. In situ activation of O₃ is achieved by the photogenerated H₂O₂, which integrates the photocatalytic hydrogen peroxide production (PHP) and advanced oxidation processes (AOPs) to form a new photocatalytic peroxone (H₂O₂/O₃) system, achieving highly efficient solar-driven degradation of recalcitrant organic pollutants in landfill leachate without the addition of external H₂O₂. The composite system exhibits efficient degradation ability for various typical pollutants in landfill leachate, among which the degradation percentage of 100 mg L⁻¹ hydroquinone (HQ) reaches 97% within 30 min. This is due to the synergistic effects of O₃ oxidation, photoactivation of O₃, activation of O₃ by EDTA-CQDs, and activation of O₃ by in situ-generated H₂O₂. In the EDTA-CQD-based H₂O₂/O₃ system, free radicals can be dynamically regenerated after the addition of pollutants, achieving sustained and efficient degradation. Therefore, in the treatment of actual leachate, the removal percentages of COD, TOC, and UV254 are nearly 90%, 70%, and 55%, respectively, demonstrating the significant advantage of this system in treating high-concentration recalcitrant organic pollutants in wastewater of complex quality. Full article

(This article belongs to the Special Issue Environmental Catalysis and Nanomaterials for Water Pollution Control)

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11 pages, 2192 KB

Open AccessArticle

Atomic-Scale Insights into Cu-Modified ZrO₂ Catalysts: The Crucial Role of Surface Clusters in Phenol Carboxylation with CO₂

by Kaihua Zhang, Sébastien Paul and Jérémie Zaffran

Catalysts 2025, 15(9), 902; https://doi.org/10.3390/catal15090902 - 18 Sep 2025

Viewed by 188

Abstract

The catalytic performance of metal oxide materials is profoundly influenced by both chemical composition and surface morphology, particularly at high dopant loadings where metallic clusters can form. Here, we use density functional theory (DFT) to elucidate how copper incorporation—either as isolated dopants or [...] Read more.

The catalytic performance of metal oxide materials is profoundly influenced by both chemical composition and surface morphology, particularly at high dopant loadings where metallic clusters can form. Here, we use density functional theory (DFT) to elucidate how copper incorporation—either as isolated dopants or as surface clusters—modulates the mechanism and activity of ZrO₂ catalysts in the direct carboxylation of phenol to para-hydroxybenzoic acid. Our results reveal that while Cu doping inhibits C–H bond activation, the presence of Cu clusters at the ZrO₂ surface dramatically lowers the barrier for C–C coupling with CO₂, owing to unique interfacial sites that facilitate substrate activation and CO₂ bending. We show that the reaction mechanism shifts from an Eley–Rideal pathway on pure ZrO₂ to a Langmuir–Hinshelwood mechanism on Cu-modified surfaces, with the rate-determining step depending on the Cu morphology. These findings demonstrate that even small amounts of metallic clusters can fundamentally alter catalytic pathways, providing actionable insights for the rational design of heterogeneous catalysts for selective aromatic carboxylation. Full article

(This article belongs to the Special Issue Predictive Modeling in Catalysis)

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15 pages, 8286 KB

Open AccessArticle

In Situ Growth of Magnesium Oxide Nanoparticles on ITO Electrodes as Electrocatalysts for Detecting Bisphenol A in Thermal Paper

by Abdullah Akhdhar and Waleed A. El-Said

Catalysts 2025, 15(9), 901; https://doi.org/10.3390/catal15090901 - 18 Sep 2025

Viewed by 287

Abstract

Here, MgO nanoparticles/ITO electrodes were fabricated through the hydrothermal method and utilized for monitoring bisphenol A (BPA). Various characterization analyses were utilized, including SEM, XRD, Raman, and FTIR techniques, to investigate the modified electrode’s morphology and structure. The modified sensor shows an LOD [...] Read more.

Here, MgO nanoparticles/ITO electrodes were fabricated through the hydrothermal method and utilized for monitoring bisphenol A (BPA). Various characterization analyses were utilized, including SEM, XRD, Raman, and FTIR techniques, to investigate the modified electrode’s morphology and structure. The modified sensor shows an LOD of 1.13 nmol L⁻¹ over a linear range of 50 nmol L⁻¹–10 µmol L⁻¹. Here, fourteen thermal paper receipt samples were randomly obtained from the local markets in Jeddah, KSA. Then, BPS was extracted and analyzed using electrochemical methods. The results indicated that (i) forty percent of the samples investigated showed high BPA levels, and (ii) twenty-seven percent of the samples showed low BPA levels, while (iii) twenty-three percent of the samples showed very low or no BPA. The significance of this study is related to its health effects, recent legal restrictions by the EU, and frequent exposure to BPA sources. Our future work will focus on achieving quantitative analysis of BPA in thermal paper samples. Furthermore, we recommend that wearing gloves be mandatory, especially for people with regular work-related exposure to thermal paper. Full article

(This article belongs to the Special Issue Electrochemical and Electrocatalysis with Porous Materials)

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18 pages, 4055 KB

Open AccessArticle

Optimizing the Microscopic Structure of MIL-68(Al) by Co-Doping for Pollutant Removal and Mechanism

by Wenju Peng, Wenjie Yang, Meng Wang, Lin Zhang, Xianxiang Liu and Yaoyao Zhang

Catalysts 2025, 15(9), 900; https://doi.org/10.3390/catal15090900 - 17 Sep 2025

Viewed by 228

Abstract

Four different MIL-68(Al) catalysts were synthesized and characterized by XPS, SEM, TEM, XRD, DLS, Nitrogen adsorption removal, and other methods. An aluminum-based MOF (Metal Organic Framework) (MIL-68(Al))/graphite oxide (GO) composite with TiO₂ showed the largest BET specific area with best adsorption performance. [...] Read more.

Four different MIL-68(Al) catalysts were synthesized and characterized by XPS, SEM, TEM, XRD, DLS, Nitrogen adsorption removal, and other methods. An aluminum-based MOF (Metal Organic Framework) (MIL-68(Al))/graphite oxide (GO) composite with TiO₂ showed the largest BET specific area with best adsorption performance. Representation demonstrated that MIL-68(Al) and TiO₂ nanoparticles are uniformly dispersed on the surface of the GO lamellar, and a tight heterojunction structure is formed between them. The MIL-68(Al)/GO/TiO₂ exhibits good pore characteristics, structural morphology, and catalytic performance. Adsorption experiments of methyl orange can reach 99.7% with the effect of MIL-68(Al)/GO/TiO₂ in water for 20 min. Moreover, the pH range can be applied to 1–13 and a high concentration of 200 mg/L methyl orange solution also worked well. In addition, this kind of catalyst can also be used for rhodamine B, methylene blue, congo red, and tetracycline in 20 min with good adsorption. Meanwhile, simple filtration can quickly recover MIL-68(Al)/GO/TiO₂ and effectively reuse it. Free radical capture experiments showed a large number of •OH radicals during the adsorption of MO (Methyl Orange) solution by MIL-68(Al)/GO/TiO₂. Meanwhile, the electrostatic interaction, π-π packing and hydrogen bonding make MIL-68(Al)/GO/TiO₂ have a higher adsorption capacity for MO. Therefore, co-doping optimized the structure of MIL-68(Al), enhancing its stability in strong acids and bases while improving adsorption performance across a broader pH range than previously reported. This work addresses the instability of MIL-68(Al) under extreme conditions, demonstrating its significant potential for wastewater treatment applications. Full article

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

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14 pages, 2226 KB

Open AccessArticle

Engineered NiCo₂O₄ Spinel Nanostructures for Enhanced Electrocatalytic Performance in Energy Storage and Non-Enzymatic Glucose Detection

by Ambikapathi Nivetha, Srirangarayan Subramanian Rakesh, Prabu P. Chidambaram, Abdullah F. Al Naim, Nazish Parveen, Senthil Alagarswamy, Sajid Ali Ansari and Mir Waqas Alam

Catalysts 2025, 15(9), 899; https://doi.org/10.3390/catal15090899 - 17 Sep 2025

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Abstract

The development of multifunctional nanostructured catalysts with high electrochemical activity and stability is crucial for sustainable technologies. Herein, we report the synthesis of CTAB-capped NiCo₂O₄ (CNC) spinel nanostructures via a facile co-precipitation method, engineered to enhance surface activity and charge [...] Read more.

The development of multifunctional nanostructured catalysts with high electrochemical activity and stability is crucial for sustainable technologies. Herein, we report the synthesis of CTAB-capped NiCo₂O₄ (CNC) spinel nanostructures via a facile co-precipitation method, engineered to enhance surface activity and charge transport. The optical and structural properties of the nanocomposite were confirmed by UV-Vis and TEM analysis, and the functional group present in the composite was confirmed by FT-IR study. The cubic spinel phase of the CNC was confirmed by XRD analysis. The band gap value was determined to be 2.15 eV, which confirmed the semiconductor nature of the nanocomposite. The photocatalytic degradation efficiency was achieved up to approximately 97% against malachite green. Additionally, CNC demonstrated excellent electrocatalytic performance in non-enzymatic glucose detection, exhibiting high sensitivity and reproducibility across a broad concentration range. Hence, the CNC acted as a potent oxidant for photoelectrochemical reactions. Full article

(This article belongs to the Special Issue Advanced Nanostructured Catalysts for the Harvesting and Storage of Electrochemical Energy)

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13 pages, 1377 KB

Open AccessFeature PaperArticle

2-(5-Phenylpyrazol-3-yl)-8-arylimino-5,6,7-trihydroquinolyliron Chlorides as Precatalysts for Ethylene Oligomerization

by Jiahao Gao, Yaling Fang, Yanping Ma, Liqun Jin, Yizhou Wang, Xinquan Hu, Wenjuan Zhang and Wen-Hua Sun

Catalysts 2025, 15(9), 898; https://doi.org/10.3390/catal15090898 - 17 Sep 2025

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Abstract

A series of 2-(5-phenylpyrazol-3-yl)-8-arylimino-5,6,7-trihydroquinolyliron chlorides (Fe1–Fe6) have been prepared and characterized by FT-IR spectra and elemental analysis. In single-crystal X-ray crystallography, Fe4 shows a distorted trigonal–bipyramidal geometry along with a self-assembling network through intermolecular NH···HO and OH···Cl hydrogen bonding. [...] Read more.

A series of 2-(5-phenylpyrazol-3-yl)-8-arylimino-5,6,7-trihydroquinolyliron chlorides (Fe1–Fe6) have been prepared and characterized by FT-IR spectra and elemental analysis. In single-crystal X-ray crystallography, Fe4 shows a distorted trigonal–bipyramidal geometry along with a self-assembling network through intermolecular NH···HO and OH···Cl hydrogen bonding. In the presence of MAO, all iron complexes perform with good activity and high selectivity for 1-butene. In addition, mixed solvents with different ratios of methylcyclohexane and toluene have been explored with a view to optimizing the catalytic performance. Full article

(This article belongs to the Special Issue Innovative Catalytic Approaches in Polymerization)

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75 pages, 36807 KB

Open AccessReview

Mechanochemistry in Waste Valorization: Advances in the Synthesis of Catalysts, Polymers, and Functional Materials

by Arthur Abinader Vasconcelos, Larissa Carla Pinheiro Gatti, Vanessa Albuquerque de Mescouto, Alex de Nazaré de Oliveira, Massimo Melchiorre, Renata Coelho Rodrigues Noronha, Rafael Luque, Roberto Esposito and Luís Adriano Santos do Nascimento

Catalysts 2025, 15(9), 897; https://doi.org/10.3390/catal15090897 - 17 Sep 2025

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Abstract

The growing accumulation of waste from diverse human activities has intensified the search for sustainable strategies. Mechanochemistry offers a promising pathway, transforming residues into high-value products with reduced energy demand, shorter reaction times, and minimal use of solvents and reagents. Various wastes—including biomass, [...] Read more.

The growing accumulation of waste from diverse human activities has intensified the search for sustainable strategies. Mechanochemistry offers a promising pathway, transforming residues into high-value products with reduced energy demand, shorter reaction times, and minimal use of solvents and reagents. Various wastes—including biomass, food residues, fly ash, used batteries, and halogenated polymers—can be converted into environmental adsorbents, industrial biopolymers, biocompatible compounds, electrodes, and catalysts. Unlike previous reviews that addressed specific waste streams, this study provides the first systematic and comparative analysis of mechanochemical valorization across multiple residues, following PRISMA guidelines (2000–2025). A total of 656 studies indexed in Scopus and Web of Science were evaluated. This integrative approach highlights recent advances, current challenges, and future prospects, offering a rigorous and transparent guide for scaling mechanochemistry toward circular and sustainable solutions. Full article

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14 pages, 2694 KB

Open AccessArticle

Precursor Engineering of SO₄²⁻-Rich CeO₂-Pt-TiO₂-Fe₂O₃ Catalyst with Oxygen Vacancy-Mediated Ternary Synergy for Ultralow-Temperature Methane Combustion

by Xiaoyi Zeng, Ruikun Zhang, Xianbing Xiang and Xianghong Fang

Catalysts 2025, 15(9), 896; https://doi.org/10.3390/catal15090896 - 17 Sep 2025

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Abstract

Current Pt-based methane combustion catalysts require high noble metal loadings (≥1 wt%) and exhibit insufficient low-temperature activity. To address this, we developed a 0.5 wt% Pt catalyst supported by sulfate-modified Fe-Ce-TiO₂ (denoted 0.5Pt/CFT-TS) via sol–gel synthesis using titanium oxysulfate (TiOSO₄) [...] Read more.

Current Pt-based methane combustion catalysts require high noble metal loadings (≥1 wt%) and exhibit insufficient low-temperature activity. To address this, we developed a 0.5 wt% Pt catalyst supported by sulfate-modified Fe-Ce-TiO₂ (denoted 0.5Pt/CFT-TS) via sol–gel synthesis using titanium oxysulfate (TiOSO₄) precursor. Control catalysts prepared with TiCl₄, titanium butoxide, or commercial TiO₂ showed inferior performance. Structural characterization revealed that the TiOSO₄ derived carrier possesses a mesoporous framework (156.2 m²/g surface area, 8.1 nm pore size) with residual SO₄²⁻ inducing strong Brønsted acidity (1.23 mmol/g NH₃ adsorption) and elevated Ce³⁺ concentration (49.45%). These properties synergistically enhanced oxygen vacancy density (51.16% O_α fraction) and stabilized sub-nm Pt nanoparticles. The resulting Pt⁰-Fe³⁺/Ce⁴⁺-Oᵥ interface facilitated dynamic redox cycling (Fe³⁺ + Ce⁴⁺ + 0.5O²⁻ ⇌ Fe²⁺ + Ce³⁺ + 0.5Oᵥ + 0.25O₂), lowering oxygen vacancy regeneration barriers (H₂-TPR peak reduced by 45 °C) and decreasing methane activation energy to 46.77 kJ/mol. This catalyst achieved T₉₀ = 163 °C and complete conversion at 450 °C under industrial conditions (1% CH₄/4% O₂, GHSV = 30,000 h⁻¹), establishing a novel design strategy for low-Pt combustion catalysts. Full article

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14 pages, 2887 KB

Open AccessArticle

Enhanced Oxygen Reduction Reaction Activity of Carbon-Supported Pt-Co Catalysts Prepared by Electroless Deposition and Galvanic Replacement

by Angeliki Banti, Ivalina Avramova, Sotiris Sotiropoulos and Jenia Georgieva

Catalysts 2025, 15(9), 895; https://doi.org/10.3390/catal15090895 - 17 Sep 2025

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Abstract

The development of effective catalysts for the oxygen reduction reaction (ORR) is crucial for improving the performance of fuel cells. Efficient carbon-supported Pt-Co nanocatalysts were successfully prepared by a generic two-step method: (i) electroless deposition of a Co-P coating on Vulcan XC72R carbon [...] Read more.

The development of effective catalysts for the oxygen reduction reaction (ORR) is crucial for improving the performance of fuel cells. Efficient carbon-supported Pt-Co nanocatalysts were successfully prepared by a generic two-step method: (i) electroless deposition of a Co-P coating on Vulcan XC72R carbon powder and (ii) subsequent spontaneous partial galvanic replacement of Co by Pt, upon immersion of the Co/C precursor in a chloroplatinate solution. The prepared Pt-Co particles (of a core-shell structure) are dispersed on a Vulcan XC-72 support, forming agglomerates made of nanoparticles smaller than 10 nm. The composition and surface morphology of the samples were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) as well as transmission electron microscopy (TEM). The crystal structures of the Co-P/C precursor and Pt-Co/C catalyst were investigated by X-ray diffraction (XRD). XPS analysis was performed to study the chemical state of the surface layers of the precursor and catalyst. The electrochemical behavior of the Pt-Co/C composites was evaluated by cyclic voltammetry (CV). Linear sweep voltammetry (LSV) experiments were used to assess the catalytic activity towards the ORR and compared with that of a commercial Pt/C catalyst. The Pt-Co/C catalysts exhibit mass-specific and surface-specific activities (of j_m = 133 mA mg⁻¹ and j_esa = 0.661 mA cm⁻², respectively) at a typical overpotential value of 380 mV (+0.85 V vs. RHE); these are superior to those of similar electrodes made of a commercial Pt/C catalyst (j_m = 50.6 mA mg⁻¹; j_esa = 0.165 mA cm⁻²). The beneficial effect of even small (<1% wt.%) quantities of Co in the catalyst on Pt ORR activity may be attributed to an optimum catalyst composition and particle size resulting from the proposed preparation method. Full article

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25 pages, 2088 KB

Open AccessReview

Microbial Spore-Based Biocatalysts: Properties, Applications and New Trends

by Brana Pantelic, Nikola Radivojevic, Ivana Aleksic, Jelena Simic and Jasmina Nikodinovic-Runic

Catalysts 2025, 15(9), 894; https://doi.org/10.3390/catal15090894 - 17 Sep 2025

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Abstract

Microbial spores are increasingly recognized as multifunctional platforms for enzyme immobilization, combining natural resilience with biotechnological versatility. Their inherent structural complexity enables high enzyme load, thermal and chemical stability, and robustness to be repeatedly used under industrially relevant conditions, largely widening their application [...] Read more.

Microbial spores are increasingly recognized as multifunctional platforms for enzyme immobilization, combining natural resilience with biotechnological versatility. Their inherent structural complexity enables high enzyme load, thermal and chemical stability, and robustness to be repeatedly used under industrially relevant conditions, largely widening their application scope. This review explores the growing role of spore-based systems in biocatalysis, from naturally active spores to engineered microbial hosts capable of producing immobilized enzymes in situ. Compared to conventional immobilization techniques, spore-based strategies offer simplified workflows, reduced environmental impact, and greater sustainability. Recent innovations also extend beyond traditional applications, introducing artificial spores and incorporating spores into biocomposite materials and biosensors. These developments reflect a shift from basic enzyme stabilization research toward scalable solutions in waste remediation, polymer degradation, green chemistry, and synthetic biology. Overall, spore-enabled biocatalysis represents a modular and robust toolset for advancing industrial biotechnology and sustainable manufacturing, instrumental in achieving a circular and bioeconomy. Full article

(This article belongs to the Special Issue Environmental Biocatalysis: From Remediation to Waste Valorization, 2nd Edition)

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56 pages, 38197 KB

Open AccessReview

Advances in Composite Photocatalysts for Efficient Degradation of Organic Pollutants: Strategies, Challenges, and Future Perspectives

by Adnan Majeed, Muhammad Adnan Iqbal and Trong-On Do

Catalysts 2025, 15(9), 893; https://doi.org/10.3390/catal15090893 - 17 Sep 2025

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Abstract

The persistent release of synthetic dyes such as methylene blue (MB) into aquatic environments poses a significant ecological hazard due to their chemical stability and toxicity. In recent years, the application of engineered composite photocatalysts has emerged as a potent solution for efficient [...] Read more.

The persistent release of synthetic dyes such as methylene blue (MB) into aquatic environments poses a significant ecological hazard due to their chemical stability and toxicity. In recent years, the application of engineered composite photocatalysts has emerged as a potent solution for efficient dye degradation under visible and UV light. This review comprehensively summarizes various advanced composites, including carbon-based, metal-doped, and heterojunction materials, tailored for MB degradation. Notably, composites such as TiO₂/C-550, WS₂/GO/Au, and MOF-derived α-Fe₂O₃/ZnO achieved near-complete degradation (>99%) within 30–150 min, while others, like ZnO/JSAC-COO⁻ and Ag/TiO₂/CNT, displayed enhanced charge separation and stability over five consecutive cycles. Band gap engineering (ranging from 1.7 eV to 3.2 eV) and reactive oxygen species (·OH, ·O₂⁻) generation were key to their photocatalytic performance. This review compares the structural attributes, synthetic strategies, and degradation kinetics across systems, highlighting the synergistic role of co-catalysts, surface area, and electron mobility. This work offers systematic insight into the state-of-the-art composite photocatalysts and provides a comparative framework to guide future material design for wastewater treatment applications. Full article

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15 pages, 1749 KB

Open AccessFeature PaperArticle

Ternary SiO₂@CuO/g-C₃N₄ Nanoparticles for Solar-Driven Photoelectrocatalytic CO₂-to-Fuel Conversion

by Zhen Li and Kwang Leong Choy

Catalysts 2025, 15(9), 892; https://doi.org/10.3390/catal15090892 - 17 Sep 2025

Viewed by 162

Abstract

Electrocatalytic CO₂ reduction driven by renewable electricity offers a sustainable approach to producing valuable chemicals, though it is often hindered by low activity and selectivity. CuO, an important transition metal oxide, exhibits unique advantages in photoelectrocatalysis due to its high intrinsic catalytic [...] Read more.

Electrocatalytic CO₂ reduction driven by renewable electricity offers a sustainable approach to producing valuable chemicals, though it is often hindered by low activity and selectivity. CuO, an important transition metal oxide, exhibits unique advantages in photoelectrocatalysis due to its high intrinsic catalytic activity and ability to serve as an active site for CO₂ reduction. SiO₂, a widely used substrate, facilitates Cu loading and increases the specific surface area of the catalyst. Meanwhile, g-C₃N₄ provides excellent visible-light responsiveness and efficient charge carrier mobility. Together, CuO, SiO₂, and g-C₃N₄ are earth-abundant, low-cost, and chemically stable, making them ideal for solar-to-fuel applications. Here, a novel ternary heterojunction photocatalyst was constructed using SiO₂, CuO, and g-C₃N₄. The heterostructure significantly improves light-harvesting efficiency, promotes efficient charge separation and transport, and simultaneously mitigates photogenerated carrier recombination and catalyst corrosion. The resulting SiO₂@CuO/g-C₃N₄ catalyst demonstrates outstanding CO₂ conversion performance, achieving a CO yield of 17 mmolg⁻¹h⁻¹ at 1.2 V_RHE with nearly 100% selectivity. Moreover, this work systematically investigates the electrocatalytic CO₂ reduction reaction (CO₂RR) mechanism on Cu-based catalysts, offering insights into the formation of high-value multicarbon products and highlighting the potential of rational heterojunction design in enhancing solar-driven fuel production efficiency. Full article

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31 pages, 1703 KB

Open AccessReview

Enzymes as Catalysts in Industrial Biocatalysis: Advances in Engineering, Applications, and Sustainable Integration

by Mohd Farhan, Ibrahim W. Hasani, Doaa S. R. Khafaga, Waleed Mahmoud Ragab, Raisa Nazir Ahmed Kazi, Mohammad Aatif, Ghazala Muteeb and Yosri A. Fahim

Catalysts 2025, 15(9), 891; https://doi.org/10.3390/catal15090891 - 16 Sep 2025

Viewed by 739

Abstract

Enzymes are highly selective and efficient biological catalysts that play a critical role in modern industrial biocatalysis. Their ability to operate under mild conditions and reduce environmental impact makes them ideal alternatives to conventional chemical catalysts. This review provides a comprehensive overview of [...] Read more.

Enzymes are highly selective and efficient biological catalysts that play a critical role in modern industrial biocatalysis. Their ability to operate under mild conditions and reduce environmental impact makes them ideal alternatives to conventional chemical catalysts. This review provides a comprehensive overview of advances in enzyme-based catalysis, focusing on enzyme classification, engineering strategies, and industrial applications. The six major enzyme classes—hydrolases, oxidoreductases, transferases, lyases, isomerases, and ligases—are discussed in the context of their catalytic roles across sectors such as pharmaceuticals, food processing, textiles, biofuels, and environmental remediation. Recent developments in protein engineering, including directed evolution, rational design, and computational modeling, have significantly enhanced enzyme performance, stability, and substrate specificity. Emerging tools such as machine learning and synthetic biology are accelerating the discovery and optimization of novel enzymes. Progress in enzyme immobilization techniques and reactor design has further improved process scalability, reusability, and operational robustness. Enzyme sourcing has expanded from traditional microbial and plant origins to extremophiles, metagenomic libraries, and recombinant systems. These advances support the integration of enzymes into green chemistry and circular economy frameworks. Despite challenges such as enzyme deactivation and cost barriers, innovative solutions continue to emerge. Enzymes are increasingly enabling cleaner, safer, and more efficient production pathways across industries, supporting the global shift toward sustainable and circular manufacturing. Full article

(This article belongs to the Special Issue Enzymatic and Chemoenzymatic Cascade Reactions)

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16 pages, 6369 KB

Open AccessArticle

Plasma–Liquid Synthesis of PLA/MXene Composite Films and Their Structural, Optical, and Photocatalytic Properties

by Nikolay Sirotkin, Anna Khlyustova and Alexander Agafonov

Catalysts 2025, 15(9), 890; https://doi.org/10.3390/catal15090890 - 16 Sep 2025

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Abstract

This study addresses the need for sustainable, high-performance photocatalytic materials by developing novel polylactide (PLA)/MXene composites. A one-step plasma-liquid synthesis method was employed, utilizing a direct current discharge between metal electrodes (Ti, Mo) in a carbon tetrachloride and PLA solution. This single-step process [...] Read more.

This study addresses the need for sustainable, high-performance photocatalytic materials by developing novel polylactide (PLA)/MXene composites. A one-step plasma-liquid synthesis method was employed, utilizing a direct current discharge between metal electrodes (Ti, Mo) in a carbon tetrachloride and PLA solution. This single-step process simultaneously exfoliates MXene nanosheets (Ti₂CCl_x, Mo₂CCl_x, Mo₂TiC₂Cl_x) and incorporates them into the polymer matrix. The resulting composite films exhibit a highly porous morphology and significantly enhanced optical absorption, with band gaps reduced to 0.62–1.15 eV, enabling efficient visible-light harvesting. The composites demonstrate excellent photocatalytic activity for degrading a mixture of organic dyes (Methylene Blue > Rhodamine B > Reactive Red 6C) under visible light. The developed plasma-liquid technique presents a streamlined, efficient route for fabricating visible-light-driven PLA/MXene photocatalysts, offering a sustainable solution for advanced water purification applications. Full article

(This article belongs to the Special Issue MXenes-Based Composites and Their Applications in Photocatalysis, Electrocatalysis and Thermocatalysis)

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12 pages, 4562 KB

Open AccessArticle

Defect Engineering via La Doping and Hydrogenation on Bi₄Ti₃O₁₂ for Synergistically Enhancing Photocatalytic CO₂ to CH₃OH

by Lijun Xue, Yuxuan Wang, Chenhui Qiu and Hui Wan

Catalysts 2025, 15(9), 889; https://doi.org/10.3390/catal15090889 - 16 Sep 2025

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Abstract

Developing highly efficient photocatalysts for CO₂ reduction remains a great challenge. The large band gap and poor charge carrier dynamics are the major factors limiting the performance of Bi₄Ti₃O₁₂ (BTO). Herein, a series of La-doped Bi₄ [...] Read more.

Developing highly efficient photocatalysts for CO₂ reduction remains a great challenge. The large band gap and poor charge carrier dynamics are the major factors limiting the performance of Bi₄Ti₃O₁₂ (BTO). Herein, a series of La-doped Bi₄Ti₃O₁₂ (BLa_xTO) nanosheets were synthesized and further modified by NaBH₄ hydrogenation to create surface defect-rich H-BLa_XTO nanosheets. Characterizations and theoretical calculations confirmed that the synergistic effect of La doping and hydrogenation significantly enhanced visible-light absorption, promoted charge separation, and improved the electron reduction capacity. When applied to photocatalytic CO₂ reduction, the H-BLa_0.2TO catalyst achieved a superior CH₃OH production rate of 7.90 μmol·g⁻¹·h⁻¹, which is 5.6 times higher than that of pristine Bi₄Ti₃O₁₂. Moreover, the H-BLa_0.2TO catalyst maintained excellent stability over four consecutive cycles. This study offers an integrated strategy for constructing high-performance bismuth-based photocatalysts through elemental doping and defect engineering. Full article

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

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13 pages, 3298 KB

Open AccessArticle

Maximally Exploiting the Fe²⁺ at the Interface of Micro and Nano Bubbles in the Fenton-Coupled Micro and Nano Bubble System for Organic Pollutant Degradation

by Qiongqiong He, Zhaoyang Song, Shaomeng Huang, Ruize Gao, Chao Han and Zhenyong Miao

Catalysts 2025, 15(9), 888; https://doi.org/10.3390/catal15090888 - 16 Sep 2025

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Abstract

Heterocyclic compounds in high-salinity wastewater are highly resistant to degradation, posing significant treatment challenges. A hybrid micro-nano bubble Fenton system (FT-MNBs) was developed to enhance Fe²⁺ activation via interfacial effects. The FT-MNBs achieved a significantly higher indole degradation rate (0.0380 min⁻¹ [...] Read more.

Heterocyclic compounds in high-salinity wastewater are highly resistant to degradation, posing significant treatment challenges. A hybrid micro-nano bubble Fenton system (FT-MNBs) was developed to enhance Fe²⁺ activation via interfacial effects. The FT-MNBs achieved a significantly higher indole degradation rate (0.0380 min⁻¹) compared with micro and nano bubbles (MNBs) alone (0.0046 min⁻¹) and conventional Fenton (0.01008 min⁻¹). In real coking wastewater with a total dissolved solid (TDS) content of 3.266 g/L, FT-MNBs achieved COD removal efficiencies of 93.42% (initial COD 200 mg/L) and 72.54% (initial COD 10,000 mg/L), demonstrating excellent adaptability and efficiency in treating refractory high-salt organic wastewater. Electron spin resonance confirmed •OH as the main reactive species. Molecular simulations revealed that the MNB interface enhances the adsorption energy of Fe and H₂O₂, alters the Fe 3d orbital to better overlap with the O–O 2p orbital, and increases electron density—thus promoting O–O bond cleavage and free radical generation. The FT-MNBs not only enhances reaction kinetics but also offer scalability and energy efficiency, showing great potential for advanced industrial wastewater treatment. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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21 pages, 3443 KB

Open AccessArticle

Comparison of Quadratic vs. Langmuir–Hinshelwood Kinetics for Formic Acid Mineralization in a Photocatalytic Film

by Giovanni Camera-Roda, Maria Papallo, Francesco Parrino, Vittorio Loddo and Leonardo Palmisano

Catalysts 2025, 15(9), 887; https://doi.org/10.3390/catal15090887 - 15 Sep 2025

Viewed by 226

Abstract

A plane reactor illuminated by LEDs was used to study the kinetics of the photocatalytic mineralization of formic acid in a TiO₂ film. Two of the most widespread types of kinetics were considered to see if their popularity is deserved. More specifically, [...] Read more.

A plane reactor illuminated by LEDs was used to study the kinetics of the photocatalytic mineralization of formic acid in a TiO₂ film. Two of the most widespread types of kinetics were considered to see if their popularity is deserved. More specifically, one-parameter quadratic-type and Langmuir–Hinshelwood-type kinetics were compared against the concentration–time experimental data at different levels of illumination. Closed-form solutions, which allow for the calculation of substrate concentration over time, were derived for the application of the integral method of kinetic analysis. The considered factors, which affect the reaction rate, were the substrate concentration and the rate of photon absorption (RPA) and were varied in order to investigate most of the possible kinetic regimes. The possible onset of limitations due to external and internal mass transfer and transport of the photons was analyzed and discussed. Thanks to the absence of such limitations in the system under examination, it was possible to appraise the “intrinsic” kinetics directly. Both the models were apt to fit the observed decrease in the substrate concentration with time, even if with different soundness. However, substantial differences between the two models were evidenced in the capabilities to reliably reproduce the effects of the RPA. Full article

(This article belongs to the Section Computational Catalysis)

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16 pages, 5701 KB

Open AccessArticle

Zn_0.8Cd_0.2S Photocatalyst Modified with Ni(OH)₂ for Enhanced Photocatalytic Hydrogen Production

by Qianran Feng, Xiaoting Yu, Jinlian Peng, Siying Du, Liuyun Chen, Xinyuan Xu and Tongming Su

Catalysts 2025, 15(9), 886; https://doi.org/10.3390/catal15090886 - 15 Sep 2025

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Abstract

Sustainable production of hydrogen is currently a global research hotspot. In this study, a Ni(OH)₂ cocatalyst was loaded on Zn_0.8Cd_0.2S to form Ni(OH)₂/ZCS composites and achieve highly efficient photocatalytic hydrogen production. After Ni(OH)₂ loading, a [...] Read more.

Sustainable production of hydrogen is currently a global research hotspot. In this study, a Ni(OH)₂ cocatalyst was loaded on Zn_0.8Cd_0.2S to form Ni(OH)₂/ZCS composites and achieve highly efficient photocatalytic hydrogen production. After Ni(OH)₂ loading, a close contact interface was established between Ni(OH)₂ and Zn_0.8Cd_0.2S, which increased the separation efficiency of the photogenerated electrons and holes. Moreover, the addition of Ni(OH)₂ increases the specific surface area and light absorption of Ni(OH)₂/Zn_0.8Cd_0.2S, and the Ni(OH)₂ can act as active sites for photocatalytic hydrogen production. The photocatalytic H₂ production rate of Ni(OH)₂/ZCS composites increases with the increase in the Ni amount. 9Ni(OH)₂/ZCS exhibited the optimum H₂ production rate of 12.88 mmol h⁻¹ g⁻¹, which was 9.9 times higher than that of Zn_0.8Cd_0.2S. When the amount of Ni(OH)₂ is further increased, the excess Ni(OH)₂ covers the active site of Zn_0.8Cd_0.2S and reduced the light absorption of Zn_0.8Cd_0.2S, resulting in a decrease in the H₂ production rate. Furthermore, the H₂ production rate of 9Ni(OH)₂/ZCS decreased from 12.88 to 5.15 mmol g⁻¹ h⁻¹ after 3 cycles. The main reason for the decline in the photocatalytic performance of Ni(OH)₂/ZCS is the photocorrosion of Zn_0.8Cd_0.2S. This study provides an innovative design for loading Ni(OH)₂ cocatalysts on Zn_0.8Cd_0.2S to improve the performance of photocatalysts. Full article

(This article belongs to the Special Issue Environmentally Friendly Catalysis for Green Future)

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