Catalysts

10 pages, 2488 KiB

Open AccessArticle

Photothermal-Assisted Photocatalytic Degradation of Antibiotic by Black g-C3N4 Materials Derived from C/N Precursors and Tetrachlorofluorescein

by Xiyuan Gao, Pengnian Shan, Weilong Shi and Feng Guo

Catalysts 2025, 15(5), 504; https://doi.org/10.3390/catal15050504 (registering DOI) - 21 May 2025

Abstract

The development of photothermal-assisted photocatalytic systems with broad-spectrum solar utilization and high charge separation efficiency remains a critical challenge for antibiotic degradation. Herein, we report novel black g-C₃N₄ (BCN) materials synthesized via a one-step thermal copolymerization strategy using C/N precursors [...] Read more.

The development of photothermal-assisted photocatalytic systems with broad-spectrum solar utilization and high charge separation efficiency remains a critical challenge for antibiotic degradation. Herein, we report novel black g-C₃N₄ (BCN) materials synthesized via a one-step thermal copolymerization strategy using C/N precursors and tetrachlorofluorescein. After the introduction of tetrachlorofluorescein, the color of the sample changes, which gives BCN enhanced light absorption and a significant photothermal effect for poorly heating-assisted photocatalysis. The synergistic coupling of photothermal and photocatalytic processes enabled the optimal BCN-U sample to achieve exceptional degradation efficiency (89% within 120 min) for a typical antibiotic (e.g., tetracycline) under an LED lamp as the visible light source, outperforming conventional yellow g-C₃N₄ (YCN-U) by a factor of 1.37. Mechanistic studies revealed that the photothermal effect facilitates carrier separation via thermal-driven electron excitation while accelerating reactive oxygen species (•OH and •O₂⁻) generation. The synergistic interplay between photocatalysis and photothermal effects, which improved mass transfer, ensures robust stability, which provides new insights into designing dual-functional carbon nitride-based materials for sustainable environmental remediation. Full article

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

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14 pages, 5171 KiB

Open AccessArticle

Cobalt-Decorated Carbonized Wood as an Efficient Electrocatalyst for Water Splitting

by Zichen Cheng, Zekun Li, Shou Huang, Junfan Pan, Jiaxian Mei, Siqi Zhang, Xingyu Peng, Wen Lu and Lei Yan

Catalysts 2025, 15(5), 503; https://doi.org/10.3390/catal15050503 - 21 May 2025

Abstract

The efficient mass transport and enhanced accessibility of active sites are crucial for high-performance electrocatalysts in water splitting. Inspired by the hierarchical structure of natural wood, we engineered a monolithic electrocatalyst, cobalt nanoparticles encapsulated in nitrogen-doped carbon layers on carbonized wood (Co@NC/CW), by [...] Read more.

The efficient mass transport and enhanced accessibility of active sites are crucial for high-performance electrocatalysts in water splitting. Inspired by the hierarchical structure of natural wood, we engineered a monolithic electrocatalyst, cobalt nanoparticles encapsulated in nitrogen-doped carbon layers on carbonized wood (Co@NC/CW), by carbonizing wood to create a three-dimensional framework with vertically aligned macropores. The unique architecture encapsulates cobalt nanoparticles within in situ-grown nitrogen-doped graphene layers on wood-derived microchannels, facilitating ultrafast electrolyte infusion and anisotropic electron transport. As a result, the optimized freestanding Co@NC/CW electrode exhibits remarkable bifunctional activity, achieving overpotentials of 403 mV and 227 mV for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, at a current density of 50 mA cm⁻². Furthermore, the integrated hybrid electrolyzer combining the HER and the OER delivers an impressive 50 A cm⁻² at a cell voltage of 1.72 V while maintaining a Faradaic efficiency near 99.5% and sustaining long-term stability over 120 h of continuous operation. Co@NC/CW also demonstrates performance in the complete decomposition of alkaline seawater, underscoring its potential for scalable applications. This wood-derived catalyst design not only leverages the natural hierarchical porosity of wood but also offers a sustainable platform for advanced electrochemical systems. Full article

(This article belongs to the Special Issue Recent Progress on Electrocatalytic Hydrogen Evolution Reaction)

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18 pages, 1751 KiB

Open AccessArticle

Natural Pyrolusite-Catalyzed Ozonation for Nanoplastics Degradation

by Victor Mello, Julia Nieto-Sandoval, Márcia Dezotti and Carmen Sans

Catalysts 2025, 15(5), 502; https://doi.org/10.3390/catal15050502 - 21 May 2025

Abstract

The increasing prevalence of polystyrene nanoplastics (PSNPs) in aquatic environments poses significant risks due to their persistence and potential toxicity. Conventional water treatment methods have proven ineffective in removing these emerging pollutants, highlighting the urgent need for sustainable and efficient treatment. This study [...] Read more.

The increasing prevalence of polystyrene nanoplastics (PSNPs) in aquatic environments poses significant risks due to their persistence and potential toxicity. Conventional water treatment methods have proven ineffective in removing these emerging pollutants, highlighting the urgent need for sustainable and efficient treatment. This study investigates the application of catalytic ozonation using natural pyrolusite (n-MnO₂) and oxalic acid (OA) as a co-catalyst for the environmentally friendly degradation of PSNPs. Key operational parameters, including pH, applied ozone dose, pyrolusite dosage, and OA concentration, were systematically evaluated. Results demonstrate that the MnO₂ + OA + O₃ system enhances the generation of reactive oxygen species (ROS), leading to improved PSNP removal while maintaining the applied ozone dose compared to the single ozonation reaction. The highest TOC removal of 75% was achieved within 30 min of treatment under optimal conditions (pH = 4, [MnO₂] = 0.5 g L⁻¹, [OA] = 10 mg L⁻¹, and ozone dose of 37.5 mg min⁻¹), with significant turbidity reduction, indicating both chemical and physical degradation of PSNPs. Catalyst reusability after three consecutive cycles confirmed minimal loss in activity, reinforcing its potential as a sustainable catalytic system. These findings highlight natural MnO₂-driven catalytic ozonation as a green and effective strategy for nanoplastic removal in water treatment applications. Full article

(This article belongs to the Special Issue Environmentally Friendly Catalysts for Energy and Water Treatment Applications)

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22 pages, 6961 KiB

Open AccessArticle

Support Effects on Fe- or Cu-Promoted Ni Catalysts Used in the Catalytic Deoxygenation of Tristearin to Fuel-like Hydrocarbons

by Great C. Umenweke, Robert Pace, Thomas Récalt, Olivier Heintz, Gilles Caboche and Eduardo Santillan-Jimenez

Catalysts 2025, 15(5), 501; https://doi.org/10.3390/catal15050501 - 21 May 2025

Abstract

Previous studies have shown that fats, oils, and greases (FOG) can be deoxygenated to fuel-like hydrocarbons over inexpensive alumina-supported Ni catalysts promoted with Cu or Fe to afford excellent yields of renewable diesel (RD). In this study, supports other than alumina—namely, SiO₂ [...] Read more.

Previous studies have shown that fats, oils, and greases (FOG) can be deoxygenated to fuel-like hydrocarbons over inexpensive alumina-supported Ni catalysts promoted with Cu or Fe to afford excellent yields of renewable diesel (RD). In this study, supports other than alumina—namely, SiO₂-Al₂O₃, Ce_0.8Pr_0.2O₂, and ZrO₂—were investigated to develop catalysts showing improved RD yields and resistance to coke-induced deactivation relative to Al₂O₃-supported catalysts. Results showed that catalysts supported on Ce_0.8Pr_0.2O₂ and ZrO₂ outperformed SiO₂-Al₂O₃-supported formulations, with 20%Ni-5%Fe/ZrO₂ affording a quantitative yield of diesel-like hydrocarbons. Notably, the abundance of weak acid sites varied considerably across the different supports, and a moderate concentration of these sites corresponded with the best results. Additionally, temperature-programmed reduction measurements revealed that Ni reduction is greatly dependent on both the identity of the promoter and catalyst support, which can also be invoked to explain catalyst performance since metallic Ni is identified as the likely active site for the deoxygenation reaction. It was also observed that Ce_0.8Pr_0.2O₂ provides high oxygen storage capacity and oxygen mobility/accessibility, which also improves catalyst activity. Full article

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

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23 pages, 3490 KiB

Open AccessReview

Rational Design Strategies for Covalent Organic Frameworks Toward Efficient Electrocatalytic Hydrogen Peroxide Production

by Yingjie Zheng, Yi Zhao, Wen Luo, Yifan Zhang, Yong Wang and Yang Wu

Catalysts 2025, 15(5), 500; https://doi.org/10.3390/catal15050500 - 21 May 2025

Abstract

Hydrogen peroxide (H₂O₂) is a versatile and environmentally friendly oxidant with broad applications in industry, energy, and environmental remediation. Electrocatalytic H₂O₂ production via the two-electron oxygen reduction reaction (2e⁻ ORR) has emerged as a sustainable [...] Read more.

Hydrogen peroxide (H₂O₂) is a versatile and environmentally friendly oxidant with broad applications in industry, energy, and environmental remediation. Electrocatalytic H₂O₂ production via the two-electron oxygen reduction reaction (2e⁻ ORR) has emerged as a sustainable alternative to traditional anthraquinone processes. Covalent organic frameworks (COFs), as a class of crystalline porous materials, exhibit high structural tunability, large surface areas, and chemical stability, making them promising electrocatalysts for 2e⁻ ORR. This review systematically summarizes recent advances in COF-based electrocatalysts for H₂O₂ production, including both metal-free and metal-containing systems. We discuss key strategies in COF design—such as dimensional modulation, linkage engineering, heteroatom doping, and post-synthetic modification—and highlight their effects on activity, selectivity, and stability. Fundamental insights into the 2e⁻ ORR mechanism and evaluation metrics are also provided. Finally, we offer perspectives on current challenges and future directions, emphasizing the integration of machine learning, conductivity enhancement, and scalable synthesis to advance COFs toward practical H₂O₂ electrosynthesis. Full article

(This article belongs to the Special Issue Powering the Future: Advances of Catalysis in Batteries)

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15 pages, 1749 KiB

Open AccessArticle

Optimizing Methane Oxidative Coupling over La₂O₃: Kinetic and Product Analysis

by Zhehao Qiu and Yulu Cai

Catalysts 2025, 15(5), 499; https://doi.org/10.3390/catal15050499 - 20 May 2025

Abstract

The oxidative coupling of methane (OCM) is a promising process for converting methane directly into more valuable ethane and ethylene. In this work, high time resolution online mass spectrometry was employed to track the OCM reaction over a commercial La₂O₃ [...] Read more.

The oxidative coupling of methane (OCM) is a promising process for converting methane directly into more valuable ethane and ethylene. In this work, high time resolution online mass spectrometry was employed to track the OCM reaction over a commercial La₂O₃ catalyst, focusing on the effects of methane to oxygen ratio, gas hourly space velocity (GHSV), and the presence of H₂O and CO in the feed gas on methane conversion and C₂ yield. The results demonstrated that an optimized GHSV (44,640 to 93,000 mL·g⁻¹·h⁻¹) and methane to oxygen ratio (CH₄/O₂ = 3) would achieve the highest methane conversion and C₂ yield at 740 °C. Furthermore, at a GHSV of 44,640 mL·g⁻¹·h⁻¹, the introduction of 1% H₂O into the reaction mixture resulted in a twofold increase in C₂ yield at 650 °C, while the addition of 1% CO led to a threefold increase in C₂ yield at 550 °C. A model in which only the front-end catalyst is active was also developed to show excellent agreement with the experimental data. The relationship between catalytic performance and the effective catalyst position in the catalyst bed provides important insights into optimizing reactor design and operating conditions to maximize C₂ yield and selectivity in the OCM reaction. Full article

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14 pages, 1490 KiB

Open AccessArticle

Catalytic Hydrodeoxygenation of Pyrolysis Volatiles from Pine Nut Shell over Ni-V Bimetallic Catalysts Supported on Zeolites

by Yujian Wu, Xiwei Xu, Xudong Fan, Yan Sun, Ren Tu, Enchen Jiang, Qing Xu and Chunbao Charles Xu

Catalysts 2025, 15(5), 498; https://doi.org/10.3390/catal15050498 - 20 May 2025

Abstract

Bio-oil is a potential source for the production of alternative fuels and chemicals. In this work, Ni-V bimetallic zeolite catalysts were synthesized and evaluated in in situ catalytic hydrodeoxygenation (HDO) of pyrolysis volatiles of pine nut shell for upgraded bio-oil products. The pH [...] Read more.

Bio-oil is a potential source for the production of alternative fuels and chemicals. In this work, Ni-V bimetallic zeolite catalysts were synthesized and evaluated in in situ catalytic hydrodeoxygenation (HDO) of pyrolysis volatiles of pine nut shell for upgraded bio-oil products. The pH and lower heating value (LHV) of the upgraded bio-oil products were improved by in situ catalytic HDO, while the moisture content and density of the oil decreased. The O/C ratio of the upgraded bio-oil products decreased significantly, and the oxygenated compounds in the pyrolysis volatiles were converted efficiently via deoxygenation over Ni-V zeolite catalysts. The highest HDO activity was obtained with NiV/MesoY, where the obtained bio-oil had the lowest O/C atomic ratio (0.27), a higher LHV (27.03 MJ/kg) and the highest selectivity (19.6%) towards target arenes. Owing to the more appropriate pore size distribution and better dispersion of metal active sites, NiV/MesoY enhanced the transformation of reacting intermediates, obtaining the dominant products of phenols and arenes. A higher HDO temperature improved the catalytic activity of pyrolysis volatiles to form more deoxygenated arenes. Higher Ni loading could generate more metal active sites, thus promoting the catalyst’s HDO activity for pyrolysis volatiles. This study contributes to the development of cost-efficient and eco-friendly HDO catalysts, which are required for producing high-quality biofuel products. Full article

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

2 pages, 118 KiB

Open AccessEditorial

Catalytic Methods for Producing Fine and Bulk Chemicals and Biomaterials from Biomass

by Indra Neel Pulidindi, Pankaj Sharma and Aharon Gedanken

Catalysts 2025, 15(5), 497; https://doi.org/10.3390/catal15050497 - 20 May 2025

Abstract

Editorial: Prevention is better than a cure, and adopting green technologies can prevent many health complications [...] Full article

(This article belongs to the Special Issue Catalytical Methods for the Production of Fine and Bulk Chemicals and Biomaterials from Biomass)

12 pages, 2424 KiB

Open AccessArticle

Growth of Two-Dimensional Edge-Rich Screwed WS₂ with High Active Site Density for Accelerated Hydrogen Evolution

by Dengchao Hu, Chaocheng Sun, Yida Wang, Fade Zhao, Yubao Li, Limei Song, Cuncai Lv, Weihao Zheng and Honglai Li

Catalysts 2025, 15(5), 496; https://doi.org/10.3390/catal15050496 - 20 May 2025

Abstract

Two-dimensional transition metal dichalcogenides have attracted considerable attention in electrocatalytic hydrogen evolution due to their unique layered structures and tunable electronic properties. However, prior research has predominantly focused on the intrinsic catalytic activity of planar few-layer structures, which offer limited exposure of edge-active [...] Read more.

Two-dimensional transition metal dichalcogenides have attracted considerable attention in electrocatalytic hydrogen evolution due to their unique layered structures and tunable electronic properties. However, prior research has predominantly focused on the intrinsic catalytic activity of planar few-layer structures, which offer limited exposure of edge-active sites due to their restricted two-dimensional geometry. Moreover, van der Waals interactions between layers impose substantial barriers to electron transport, significantly hindering charge transfer efficiency. To overcome these limitations, this study presents the innovative synthesis of high-quality single-screw WS₂ with a 5° dislocation angle via physical vapor deposition. Second harmonic generation measurements revealed a pronounced asymmetric polarization response, while the selected area electron diffractionand atomic force microscopy elucidated the material’s distinctive screwed dislocation configuration. In contrast to planar monolayer WS₂, the conical/screw-structured WS₂—formed through screw-dislocation-mediated growth—exhibits a higher density of exposed edge-active catalytic sites and enhanced electron transport capabilities. Electrochemical performance tests revealed that in an alkaline medium, the screwed WS₂ nanosheets exhibited an overpotential of 310 mV at a current density of −10 mA/cm², with a Tafel slope of 204 mV/dec. Additionally, under a current density of 18 mA/cm², the screwed WS₂ can sustain this current density for at least 30 h. These findings offer valuable insights into the design of low-cost, high-efficiency, non-precious metal catalysts for hydrogen evolution reactions. Full article

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

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16 pages, 942 KiB

Open AccessArticle

Supported TiO₂ Photocatalysis of Spiked Contaminants in Water and Municipal Wastewater

by Zouhour Rajah, Houda Dhibi, Mariem Abdelkader, Eva Rodriguez, Monia Guiza and Francisco Javier Rivas

Catalysts 2025, 15(5), 495; https://doi.org/10.3390/catal15050495 - 20 May 2025

Abstract

An aqueous mixture of three compounds (atrazine, carbamazepine, and p-chlorobenzoic acid) has been treated by photochemical processes including photolysis and photocatalysis with 10.7% TiO₂ supported on ceramic foams of mullite. Experiments were conducted in both ultrapure water and in a secondary effluent [...] Read more.

An aqueous mixture of three compounds (atrazine, carbamazepine, and p-chlorobenzoic acid) has been treated by photochemical processes including photolysis and photocatalysis with 10.7% TiO₂ supported on ceramic foams of mullite. Experiments were conducted in both ultrapure water and in a secondary effluent from a municipal wastewater treatment plant. Radiation at 365 nm was totally inefficient in the photolytic process carried out in ultrapure water; however, some sensitization phenomena were observed when municipal wastewater was used as a bulk matrix. In the latter case, conversion values in the range of 20–30% were obtained after 2 h. The photocatalytic process was much more effective experiencing conversions above 80% after just 80 min of reaction. The nature of the matrix used exerted a significant influence. Use of municipal wastewater slowed down the process due to the scavenging character of the natural organic matter content. Test runs in the presence of carbonates and t-butyl alcohol suggested that radical carbonates play some role in contaminant abatement, and secondary radicals generated after the t-BuOH attack by HO^● radicals should also be considered in the reaction mechanism. A pseudo-empirical mechanism of reactions sustains the experimental result obtained, acceptably modeling the effects of a water matrix, scavenger addition, and radiation volumetric photon flux. Full article

(This article belongs to the Special Issue Advancements in Photocatalysis for Environmental Applications)

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9 pages, 864 KiB

Open AccessArticle

Mild and Effective Decatungstate-Catalyzed Degradation of Methyl Orange Under Visible Light

by Wenfeng Wu, Lin Yu, Lei Zha, Feifei He, Jiajia Ma, Ouyang Wu, Huanhuan Zhang, Xinlan Chen, Shuyin Yu, Mengjing Lei, Lin-Lin Yang, Jiangang Chen and Xiai Luo

Catalysts 2025, 15(5), 494; https://doi.org/10.3390/catal15050494 - 20 May 2025

Abstract

Decatungstate (DT) is a highly promising photocatalyst for dioxygen (O₂)-based reactions but has hardly been applied in the photocatalytic degradation technology of dye. Here, we synthesized hydrophilic DT–SO₃H salts by incorporating tetra-alkyl cations with sulfonic acid groups, aiming to [...] Read more.

Decatungstate (DT) is a highly promising photocatalyst for dioxygen (O₂)-based reactions but has hardly been applied in the photocatalytic degradation technology of dye. Here, we synthesized hydrophilic DT–SO₃H salts by incorporating tetra-alkyl cations with sulfonic acid groups, aiming to enhance both the water solubility and catalytic efficiency of DT under visible light. Comprehensive characterization of DT–SO₃H using ultraviolet–visible spectroscopy (UV–Vis), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Photocurrent (PTC), and Electrochemical Impedance Spectroscopy (EIS) confirmed its improved properties. DT–SO₃H demonstrated outstanding photocatalytic performance, achieving 90% degradation of methyl orange within 25 min under continuous visible light irradiation. This study presents a cost-effective and efficient method for degrading methyl orange, representing a significant advancement in the development of high-performance photocatalysts and opening new avenues for the study and application of photocatalytic dye degradation technologies. Full article

(This article belongs to the Section Photocatalysis)

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18 pages, 4846 KiB

Open AccessArticle

Evaluation of Vacuum Residue Decomposition Kinetics with a Catalyst by Thermogravimetric Analysis

by Daulet Makenov, Almas Tusipkhan, Akmaral Zh. Sarsenbekova, Murzabek Baikenov, Nazerke Balpanova, Darzhan Aitbekova, Alma Tateeva, Dariya Izbastenova, Bibimariyam Kokzhalova and Fengyun Ma

Catalysts 2025, 15(5), 493; https://doi.org/10.3390/catal15050493 - 20 May 2025

Abstract

The study of thermal developments of heavy oil feedstock, vacuum residue in particular, is a relevant factor for the development of technologies for the processing and production of petroleum products. This paper investigates the process of thermal decomposition of the vacuum residue in [...] Read more.

The study of thermal developments of heavy oil feedstock, vacuum residue in particular, is a relevant factor for the development of technologies for the processing and production of petroleum products. This paper investigates the process of thermal decomposition of the vacuum residue in the manufacturing of catalyst and polymer material using thermal analysis methods, including thermogravimetric analysis (TGA) in isothermal and dynamic modes. Particular attention is paid to the measurement of kinetic parameters of thermolysis using model and non-model methods, which allows us to assess the output power and other kinetic characteristics of decomposition. The results obtained can be used for the development of new oil refining technologies for significantly increasing the efficiency and safety of processes. During the course of this study, experimental and theoretical activation energy values were obtained for the vacuum residue without a catalyst (experimentally: 91.54 kJ mol⁻¹/theoretically: 91.35 kJ mol⁻¹) and a sample with the presence of a catalyst (experimentally: 89.68 kJ mol⁻¹/theoretically: 90.87 kJ mol⁻¹). The reduction in activation energy in the presence of the catalyst confirms its catalytic activity and potential for processing heavy hydrocarbon feedstock. Full article

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21 pages, 1985 KiB

Open AccessArticle

Antimony- and Bismuth-Based Ionic Liquids as Efficient Adsorbents for the Removal of Dyes

by Anham Zafar, Nouman Rafique, Saadia Batool, Muhammad Saleem, Aiyeshah Alhodaib and Amir Waseem

Catalysts 2025, 15(5), 492; https://doi.org/10.3390/catal15050492 - 19 May 2025

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Abstract

A series of ionic liquids consisting of anilinium cations with varying alkyl chains and metallic (Sb and Bi) halides as anions have been synthesized and thoroughly characterized by using multinuclear (¹H and ¹³C) NMR, FT-IR, Raman and XPS techniques. They [...] Read more.

A series of ionic liquids consisting of anilinium cations with varying alkyl chains and metallic (Sb and Bi) halides as anions have been synthesized and thoroughly characterized by using multinuclear (¹H and ¹³C) NMR, FT-IR, Raman and XPS techniques. They have been exploited as adsorbents for the dye’s removal, such as malachite green, rhodamine B and Sudan II, from the aqueous solution. Various parameters like the effect of stirring rate, pH, reaction time, adsorbent amount and initial dye concentration have been optimized. Both antimony- and bismuth-based ionic liquids exhibit high adsorption efficiencies and have comparable performance for each dye. Kinetic data have been analyzed by applying kinetic models, and the best-fitted model was found to be pseudo-second order with an R² value greater than 0.98. Adsorption capacity has been determined by analyzing the sorption data using the Langmuir and Freundlich equations, and the Langmuir isotherm model has been found to be the best fitting. The maximum adsorption capacities (q_max) derived from the Langmuir isotherm for malachite green, Sudan II and rhodamine B by M-Sb ILs were 217.36, 162.10 and 62.94 mg·g⁻¹, whereas by M-Bi ILs, the adsorption capacities were slightly higher, at 230.18, 170.00 and 64.21 mg·g⁻¹, respectively. Kinetic studies indicated pseudo-second-order behavior (R² > 0.98), while thermodynamic analysis demonstrated an endothermic adsorption, and a spontaneous reaction was carried out by a physisorption process. These findings accentuate the potential of Sb- and Bi-based ionic liquids as efficient and reusable adsorbents for removing dyes from wastewater. Full article

(This article belongs to the Special Issue Advanced Catalytic Materials and Processes for Water/Wastewater Treatment)

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15 pages, 2053 KiB

Open AccessFeature PaperArticle

Kinetic Understanding of the Enhanced Electroreduction of Nitrate to Ammonia for Co₃O₄–Modified Cu₂₊₁O Nanowire Electrocatalyst

by Hao Yu, Shen Yan, Jiahua Zhang and Hua Wang

Catalysts 2025, 15(5), 491; https://doi.org/10.3390/catal15050491 - 19 May 2025

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Abstract

Electrocatalytic nitrate reduction reaction (NO₃⁻RR) to ammonia (NH₃) presents an alternative, sustainable approach to ammonia production. However, the existing catalysts suffer from poor NH₃ yield under lower concentrations of NO₃⁻, and the kinetic understanding [...] Read more.

Electrocatalytic nitrate reduction reaction (NO₃⁻RR) to ammonia (NH₃) presents an alternative, sustainable approach to ammonia production. However, the existing catalysts suffer from poor NH₃ yield under lower concentrations of NO₃⁻, and the kinetic understanding of bimetal catalysis is lacking. In this study, a Co₃O₄–modified Cu₂₊₁O nanowire (CoCuNWs) catalyst with a high specific surface area was synthesized to effectively produce NH₃ from a 10 mM KNO₃ basic solution. CoCuNWs demonstrated a high NH₃ yield rate of 0.30 mmol h⁻¹ cm⁻² with an NH₃ Faradaic efficiency (FE) of 96.7% at −0.2 V vs. RHE, which is 1.5 times higher than the bare Cu₂₊₁O NWs. The synergistic effect between Co₃O₄ and Cu₂₊₁O significantly enhanced both the nitrate conversion and ammonia yield. Importantly, it is revealed that the surface of CoCuNWs is kinetically more easily saturated with NO₃⁻ (NO₂⁻) ions than that of Cu₂₊₁O NWs, as evidenced by both the higher current density and the plateau occurring at higher NO_x⁻ concentrations. In addition, CoCuNWs exhibit a higher diffusion coefficient of NO₃⁻, being 1.6 times higher than that of Cu₂₊₁O NWs, which also indicates that the presence of Co₃O₄ could promote the diffusion and adsorption of NO₃⁻ on CoCuNWs. Moreover, the ATR–SEIRAS analysis was applied to illustrate the reduction pathway of NO₃⁻ to NH₃ on CoCuNWs, which follows the formation of the key intermediate from *NO₂⁻, *NO, *NH₂OH to *NH₃. This work presents a strategy for constructing dual–metal catalysts for NO₃⁻RR and provides an insight to understand the catalysis from the perspective of the kinetics. Full article

(This article belongs to the Special Issue Powering the Future: Advances of Catalysis in Batteries)

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19 pages, 2133 KiB

Open AccessFeature PaperArticle

Electrodeposited Co Crystalline Islands Shelled with Facile Spontaneously Deposited Pt for Improved Oxygen Reduction

by Jelena Golubović, Lazar Rakočević, Vladimir Rajić, Miloš Milović and Svetlana Štrbac

Catalysts 2025, 15(5), 490; https://doi.org/10.3390/catal15050490 - 18 May 2025

Viewed by 174

Abstract

The cobalt crystalline islands (Co_cryst) were electrochemically deposited onto a glassy carbon (GC) support and then modified by a facile spontaneous deposition of platinum. The electrocatalytic activity of the resulting Co_cryst-Pt core-shell catalyst was evaluated for the oxygen reduction [...] Read more.

The cobalt crystalline islands (Co_cryst) were electrochemically deposited onto a glassy carbon (GC) support and then modified by a facile spontaneous deposition of platinum. The electrocatalytic activity of the resulting Co_cryst-Pt core-shell catalyst was evaluated for the oxygen reduction reaction (ORR) in an alkaline medium. The XRD characterization of the Co_cryst-Pt islands revealed that the cobalt core had a hexagonal close-packed (hcp) crystalline structure, and that the platinum shell exhibited a crystalline structure with a preferential (111) orientation. SEM images showed that the average lateral size of the Co_cryst islands was 1.17 μm, which increased to 1.32 μm after adding platinum. The XPS analysis indicated that the outer layer of the bulk metallic Co_cryst islands was fully oxidized. During the spontaneous deposition of platinum, the outer Co(OH)₂ layer was dissolved, leaving the cobalt core in a metallic state, while the platinum shell remained only partially oxidized. The high electrochemically active surface area of the Co_cryst-Pt/GC electrode, along with a suitable crystalline structure of the Co_cryst-Pt islands, contributes to enhancing its ORR activity by providing a greater number of surface active sites for oxygen adsorption and subsequent reduction. The ORR on the Co_cryst-Pt catalyst occurs via a four-electron reaction pathway, with onset and half-wave potentials of 1.07 V and 0.87 V, respectively, which exceed those of polycrystalline platinum and a commercial benchmark Pt/C. Full article

(This article belongs to the Special Issue Insight into Electrocatalysts for Oxygen Reduction Reaction)

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22 pages, 6513 KiB

Open AccessArticle

Sustainable MgO Nanocatalyst Additives for Boosting Performance and Mitigating Emissions of Used Cooking Oil Biodiesel–Diesel Blends in Compression Ignition Engines

by Kiran Chaudhari, Nilesh Salunke, Shakeelur Raheman Ateequr Raheman, Khursheed B. Ansari, Kapil Ashokrao Saner, Vijay Kashinath Suryawanshi and Mumtaj Shah

Catalysts 2025, 15(5), 489; https://doi.org/10.3390/catal15050489 - 17 May 2025

Viewed by 219

Abstract

With conventional fuels dwindling and emissions rising, there is a necessity to develop and assess innovative substitute fuel for compression ignition (CI) engines. This study investigates the potential of magnesium oxide (MgO) nanoparticles as a sustainable additive to enhance the performance and reduce [...] Read more.

With conventional fuels dwindling and emissions rising, there is a necessity to develop and assess innovative substitute fuel for compression ignition (CI) engines. This study investigates the potential of magnesium oxide (MgO) nanoparticles as a sustainable additive to enhance the performance and reduce emissions of used cooking oil (UCO) biodiesel–diesel blends in CI engines. MgO nanoparticles were biosynthesized using Citrus aurantium peel extract, offering an environmentally friendly production method. A single-cylinder CI engine was used to test the performance of diesel fuel (B0), a 20% biodiesel blend (B20), and B20 blends with 30 ppm (B20M30) and 60 ppm (B20M60) MgO nanoparticles. Engine performance parameters (brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), and exhaust gas temperature (EGT)) and emission characteristics (CO, NO_x, unburnt hydrocarbons (HCs), and smoke opacity) were measured. The B20M60 blend showed a 2.38% reduction in BSFC and a 3.38% increase in BTE compared to B20, with significant reductions in unburnt HC, CO, and smoke opacity. However, NO_x emissions increased by 6.57%. The green synthesis method enhances sustainability, offering a promising pathway for cleaner and more efficient CI engine operation using UCO biodiesel, demonstrating the effectiveness of MgO nanoparticles. Full article

(This article belongs to the Special Issue Waste-to-Resources Through Catalysis in Green and Sustainable Way)

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16 pages, 649 KiB

Open AccessArticle

Research on Catalysts for Online Ammonia Hydrogen Production in Marine Engines: Performance Evaluation and Reaction Kinetic Modeling

by Jin Wu, Liang Yang, Chuang Xiang, Junjie Liang, He Yang, Dilong Li, Ying Sun, Lin Lv and Neng Zhu

Catalysts 2025, 15(5), 488; https://doi.org/10.3390/catal15050488 - 17 May 2025

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Abstract

One viable technical approach for achieving hydrogen-blended combustion in marine ammonia-fueled engines is to utilize online ammonia decomposition to produce hydrogen, which is then introduced into the engine for combustion. This work carried out ammonia decomposition experiments using various catalysts, examining the effects [...] Read more.

One viable technical approach for achieving hydrogen-blended combustion in marine ammonia-fueled engines is to utilize online ammonia decomposition to produce hydrogen, which is then introduced into the engine for combustion. This work carried out ammonia decomposition experiments using various catalysts, examining the effects of temperature and space velocity on Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 and Ni/Ce_0.36Zr_0.64O₂ catalysts. Based on the experimental data obtained, the kinetic parameters of ammonia decomposition were fitted using four different models: mass action law, first-order reaction, Langmuir, and Temkin–Pyzhev kinetics across two catalysts, with the subsequent mechanistic analysis of catalytic reaction processes within the reactor. The results revealed that the NH₃ conversion rate of the Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 catalyst was superior to that of the Ni/Ce_0.36Zr_0.64O₂ catalyst, with temperature activity windows of 250–450 °C and 400–600 °C, respectively. Within the range of 2000–32,000 mL·g⁻¹·h⁻¹), an increase in space velocity led to a decrease in NH₃ conversion rate by approximately half. All four models were able to predict NH₃ conversion rates for the different catalysts with reasonable accuracy. The activation energies for Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 and Ni/Ce_0.36Zr_0.64O₂ catalysts were found to be 37.7 kJ·mol⁻¹ and 66 kJ·mol⁻¹, respectively. Targeting hydrogen requirements of 10–40% vol for ammonia engines, the corresponding catalytic temperatures for Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 and Ni/Ce_0.36Zr_0.64O₂ were above 267 °C and 500 °C, respectively. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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11 pages, 2195 KiB

Open AccessArticle

Highly Dispersed Pt on TiO_x Embedded in Porous Carbon as Electrocatalyst for Hydrogen Evolution Reaction

by Zihan Wei, Xin Chen, Pengfei Diao, Jiayi Liao, Zhaonan Chong, Change Yao, Zhong Ma and Guisheng Li

Catalysts 2025, 15(5), 487; https://doi.org/10.3390/catal15050487 - 17 May 2025

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Abstract

In conventionally used carbon-supported heterogeneous platinum catalysts for hydrogen evolution reaction (HER), low Pt utilization efficiency and poor stability, resulting from weak interactions with the carbon supports, are crucial issues. Here, we report a novel hierarchical structure of TiO_x nanoparticles embedded in [...] Read more.

In conventionally used carbon-supported heterogeneous platinum catalysts for hydrogen evolution reaction (HER), low Pt utilization efficiency and poor stability, resulting from weak interactions with the carbon supports, are crucial issues. Here, we report a novel hierarchical structure of TiO_x nanoparticles embedded in porous carbon with the in situ growth of highly dispersed Pt on the TiO_x surface (Pt-TiO_x@C). The as-prepared Pt-TiO_x@C electrocatalyst showed excellent catalytic activity during HER with an overpotential of only 10 mV when the current density reached 10 mA cm⁻² and the mass activity was 9.24 A mg_Pt⁻¹ at an overpotential of 30 mV in 0.5 M H₂SO₄ solution, thus outperforming commercial Pt/C catalysts. Furthermore, it also exhibited highly stable catalytic activity over 10,000 CV cycles of an accelerated degradation test (ADT). This high HER activity and durability could be ascribed to the highly dispersed Pt feature and the strong metal–support interaction (SMSI) between Pt and TiO_x. This study also provides a simple and effective method for designing highly active and stable electrocatalysts. Full article

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15 pages, 5139 KiB

Open AccessArticle

Synchronous Removal of Organic Pollutants and Phosphorus from Emergency Wastewater in Chemical Industry Park by Plasma Catalysis System Based on Calcium Peroxide

by Aihua Li, Chengjiang Qian, Jinfeng Wen and Tiecheng Wang

Catalysts 2025, 15(5), 486; https://doi.org/10.3390/catal15050486 - 16 May 2025

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Abstract

This study employs a plasma-coupled calcium peroxide (CaO₂) system to degrade tetracycline (TC) and remove phosphorus from emergency wastewater in a chemical industry park. The plasma/CaO₂ system achieves optimal performance when the CaO₂ dosage reaches 0.13 g/L. Higher degradation [...] Read more.

This study employs a plasma-coupled calcium peroxide (CaO₂) system to degrade tetracycline (TC) and remove phosphorus from emergency wastewater in a chemical industry park. The plasma/CaO₂ system achieves optimal performance when the CaO₂ dosage reaches 0.13 g/L. Higher degradation efficiencies of TC were observed at increased discharge voltages, frequencies, and under weakly acidic and weakly alkaline conditions. Variations in discharge voltage and frequency have no significant impact on the phosphorus removal efficiency, but weakly alkaline conditions favor phosphorus removal. The reactive species (·OH, ¹O₂, O₂·⁻) within the plasma/CaO₂ system were identified, and their roles were elucidated using radical scavengers. Subsequently, the degradation process was characterized by measuring changes in total organic carbon (TOC), chemical oxygen demand (COD), and ammonia nitrogen during the reaction, along with three-dimensional fluorescence analysis and ultraviolet-visible spectroscopy (UV-Vis). Eight intermediate products were identified through LC-MS, and two degradation pathways were clarified based on density functional theory. The toxicity analysis of the intermediate products demonstrated that the plasma/CaO₂ system is an efficient, feasible, and environmentally friendly method for the synchronous removal of organic pollutants and phosphorus from emergency wastewater in a chemical industry park. Full article

(This article belongs to the Special Issue Plasma Catalysis for Environment and Energy Applications)

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21 pages, 6029 KiB

Open AccessFeature PaperArticle

Exploring Perhydro-Benzyltoluene Dehydrogenation Using Sulfur-Doped PtMo/Al₂O₃ Catalysts

by Kevin Alconada, Fatima Mariño, Ion Agirre and Victoria Laura Barrio

Catalysts 2025, 15(5), 485; https://doi.org/10.3390/catal15050485 - 16 May 2025

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Abstract

This study investigates the dehydrogenation of perhydrobenzyltoluene, a Liquid Organic Hydrogen Carrier (LOHC), using sulfur-doped bimetallic PtMo/Al₂O₃ catalysts. Based on previous research that highlighted the superior performance of PtMo catalysts over monometallic Pt catalysts, this work focuses on minimizing byproduct [...] Read more.

This study investigates the dehydrogenation of perhydrobenzyltoluene, a Liquid Organic Hydrogen Carrier (LOHC), using sulfur-doped bimetallic PtMo/Al₂O₃ catalysts. Based on previous research that highlighted the superior performance of PtMo catalysts over monometallic Pt catalysts, this work focuses on minimizing byproduct formation, specifically methylfluorene, through sulfur doping. Catalysts with low platinum content (<0.3 wt.%) were synthesized using the wet impregnation method by varying sulfur concentrations to study their impact on catalytic activity. Characterization techniques, including CO–DRIFT and CO–TPD, revealed the role of sulfur in selectively blocking low-coordinated Pt sites, thus improving selectivity and maintaining high dispersion. Catalytic tests revealed that samples with ≥0.1 wt.% sulfur achieved up to a threefold reduction in methylfluorene formation compared to the unpromoted PtMo/Al₂O₃ sample, with a molar fraction below 2% at 240 min. In parallel, these samples reached a degree of dehydrogenation (DoD) above 85% within 240 min, demonstrating that improved selectivity can be achieved without compromising catalytic performance. Full article

(This article belongs to the Special Issue Catalysts for Energy Storage)

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16 pages, 3239 KiB

Open AccessArticle

Cu-Sn Electrocatalyst Prepared with Chemical Foaming and Electroreduction for Electrochemical CO₂ Reduction

by Caibo Zhu, Ao Yu, Yin Zhang, Wenbo Chen, Zhijian Wu, Manni Xu, Deyu Qu, Junxin Duan and Xi Li

Catalysts 2025, 15(5), 484; https://doi.org/10.3390/catal15050484 - 16 May 2025

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Abstract

The conversion of CO₂ through the electrochemical reduction reaction (ECO₂RR) into chemicals or fuels is regarded as one of the effective ways to decrease atmospheric CO₂ concentrations. In this study, a Cu-Sn bimetallic electrocatalyst (ER-Sn_mCu_nO [...] Read more.

The conversion of CO₂ through the electrochemical reduction reaction (ECO₂RR) into chemicals or fuels is regarded as one of the effective ways to decrease atmospheric CO₂ concentrations. In this study, a Cu-Sn bimetallic electrocatalyst (ER-Sn_mCu_nO_x-t/CC) was successfully prepared via a chemical foaming method and electrochemical reduction. SEM showed that ER-Sn₁Cu₁O_x-500 nanoparticles were uniformly distributed on the carbon cloth, which benefited from foaming. The XPS results demonstrated the synergistic interaction between Cu and Sn and the existence of oxygen vacancies originating from the electroreduction. Due to the above features, ER-Sn₁Cu₁O_x-500/CC achieved 84.1% FE for HCOOH at −1.1 V vs. RHE, and the corresponding J_HCOOH was up to 32.4 mA·cm⁻² in the H-type cell. Especially in the flow cell, ER-Sn₁Cu₁O_x-500/GDE could reach a high J_HCOOH of 190 mA·cm⁻² at −1.1 V vs. RHE and maintained J_HCOOH higher than 100 mA·cm⁻² for 24 h with a formic acid selectivity over 70%, indicating both excellent catalytic activity and high HCOOH selectivity. In situ FTIR results revealed that synergism between Cu and Sn could regulate the adsorption of intermediates, thus enhancing the catalytic performance of ER-Sn₁Cu₁O_x-500 for ECO₂RR. Full article

(This article belongs to the Section Electrocatalysis)

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16 pages, 1982 KiB

Open AccessArticle

Selective Catalytic Reduction of NO with H₂ over Pt/Pd-Containing Catalysts on Silica-Based Supports

by Magdalena Jabłońska, Adrián Osorio Hernández, Jürgen Dornseiffer, Jacek Grams, Anqi Guo, Ulrich Simon and Roger Gläser

Catalysts 2025, 15(5), 483; https://doi.org/10.3390/catal15050483 - 15 May 2025

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Abstract

Platinum- and/or palladium-containing silica-based supports were applied for the selective catalytic reduction of NO_x with hydrogen (H₂-SCR-DeNO_x). To obtain enhanced activity and N₂ selectivity below 150 °C, we varied the type and loading of noble metals (Pt [...] Read more.

Platinum- and/or palladium-containing silica-based supports were applied for the selective catalytic reduction of NO_x with hydrogen (H₂-SCR-DeNO_x). To obtain enhanced activity and N₂ selectivity below 150 °C, we varied the type and loading of noble metals (Pt and Pd both individually and paired, 0.1–1.0 wt.-%), silica-containing supports (ZrO₂/SiO₂, ZrO₂/SiO₂/Al₂O₃, Al₂O₃/SiO₂/TiO₂), as well as the H₂ concentration in the feed (2000–4000 ppm). All of these contributed to enhancing N₂ selectivity during H₂-SCR-DeNO_x over the (0.5 wt.-%)Pt/Pd/ZrO₂/SiO₂ catalyst in the presence of 10 vol.-% of O₂. H₂ was completely consumed at 150 °C. A comparison of the catalytic results obtained during H₂-SCR-DeNO_x,(H₂-)NH₃-SCR-DeNO_x, as well as stop-flow H₂-SCR-DeNO_x and temperature-programmed studies, revealed that in the temperature range between 150 and 250 °C, the continuously coupled or overlaying mechanism of NO reduction by hydrogen and ammonia based on NH₃ formation at lower temperatures, which is temporarily stored at the acid sites of the support and desorbed in this temperature range, could be postulated. Full article

(This article belongs to the Topic Advanced Materials in Chemical Engineering)

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12 pages, 1865 KiB

Open AccessFeature PaperArticle

Efficient Synthesis of Tetrasubstituted Furans via Lipase-Catalyzed One-Pot Sequential Multicomponent Reaction

by Yongqi Zeng, Yong Tang, Minglu Xu, Dantong Wang, Zhi Wang, Yin Gao and Lei Wang

Catalysts 2025, 15(5), 482; https://doi.org/10.3390/catal15050482 - 15 May 2025

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Abstract

Tetrasubstituted furans and their derivatives represent a versatile class of important heterocyclic frameworks widely distributed in natural products. These scaffolds also demonstrate significant potential in pharmaceutical chemistry, materials science, and organic synthesis methodologies. In this study, we successfully established a synergistic catalytic system [...] Read more.

Tetrasubstituted furans and their derivatives represent a versatile class of important heterocyclic frameworks widely distributed in natural products. These scaffolds also demonstrate significant potential in pharmaceutical chemistry, materials science, and organic synthesis methodologies. In this study, we successfully established a synergistic catalytic system utilizing benzoylacetonitriles, aldehydes, and benzoyl chlorides as substrates, facilitated by tributylphosphine and immobilized lipase (Novozym 435), to achieve efficient synthesis of cyano-containing tetrasubstituted furans. Under optimized conditions, we obtained a series of target products exhibiting exceptional substrate tolerance with good to excellent isolated yields ranging from 80% to 94%. Additionally, we proposed a reasonable reaction mechanism and verified it through controlled experiments. This methodology not only expands the synthetic utility of lipase in non-natural transformations but also establishes a paradigm of green chemistry for the construction of tetrasubstituted furans. Full article

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

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25 pages, 1620 KiB

Open AccessFeature PaperArticle

Laccase-Catalyzed Polymerized Natural Bioactives for Enhanced Mushroom Tyrosinase Inhibition

by Diana Costa, Diana Rocha, Joana Santos, Jennifer Noro, Artur Ribeiro and Carla Silva

Catalysts 2025, 15(5), 481; https://doi.org/10.3390/catal15050481 - 14 May 2025

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Abstract

Skin hyperpigmentation disorders, such as melasma, are linked to excessive melanin production, primarily regulated by the enzyme tyrosinase (TYR). While current inhibitors like kojic acid (KA) are effective, they often cause adverse side effects, driving the search for safer andnatural alternatives. This study [...] Read more.

Skin hyperpigmentation disorders, such as melasma, are linked to excessive melanin production, primarily regulated by the enzyme tyrosinase (TYR). While current inhibitors like kojic acid (KA) are effective, they often cause adverse side effects, driving the search for safer andnatural alternatives. This study evaluated the TYR inhibitory potential of bioactive-rich extracts from acorn, cocoa, cork, and eucalyptus, extracted using hydroethanolic (HE) and natural deep eutectic solvents (NADES), and explored the enhancement of their bioactivity through laccase-assisted polymerization. NADES significantly improved extraction yields and preserved bioactive compounds, with cocoa extracts showing the highest TYR inhibition. Laccase-mediated polymerization further enhanced TYR inhibitory activity, particularly of NADES extracts, suggesting a more effective and sustainable approach for skincare applications. The results highlight the potential of combining green chemistry principles with enzymatic catalysis to develop eco-friendly and efficient treatments for hyperpigmentation disorders, offering a promising alternative to conventional methods. Full article

(This article belongs to the Special Issue The Design of Protein-Based Catalysts)

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9 pages, 8032 KiB

Open AccessFeature PaperArticle

Cyclic Stability of a Bifunctional Catalyst in the Sorption-Enhanced Reverse Water–Gas Shift Reaction

by Johannis A. Z. Pieterse, Saskia Booneveld, Gerard D. Elzinga, Vladimir Dikic, Galina Skorikova, Jurriaan Boon and Andreas Geisbauer

Catalysts 2025, 15(5), 480; https://doi.org/10.3390/catal15050480 - 13 May 2025

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Abstract

Sorption-enhanced reverse water–gas shift (SE-RWGS), designated as COMAX, was studied using a Pt4A bifunctional catalyst (reactive adsorbent). The bifunctional Pt4A catalyst integrates CO₂ activation and reaction with water adsorption functionality, where the active phase is loaded onto a carrier that provides a [...] Read more.

Sorption-enhanced reverse water–gas shift (SE-RWGS), designated as COMAX, was studied using a Pt4A bifunctional catalyst (reactive adsorbent). The bifunctional Pt4A catalyst integrates CO₂ activation and reaction with water adsorption functionality, where the active phase is loaded onto a carrier that provides a surface area for Pt dispersion as well as H₂O adsorption capacity. The 0.3 wt% Pt-4A molecular sieve reactive sorbent was tested at a kg scale in a pressure swing (reactive) adsorption–regeneration process. More than 400 cycles over 50 days of operation were successfully demonstrated without significant decay. Cyclic stability was achieved, provided that the regeneration temperature was sufficiently high to ensure near-complete dehydration. The single-bead structure withstood the pressure swing operation effectively, with only a maximum of 2% of the total recovered reactive sorbent turning to fines (<500 μm). The successful integration of catalytic activity and water adsorption capacity into a single particle presents opportunities for the further intensification of sorption-enhanced reactions for CO₂ conversion. Full article

(This article belongs to the Special Issue Catalytic Activity on Thermochemical and Non-Thermal Plasma Conversion/Utilization of Methane and Carbon Dioxide)

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25 pages, 8285 KiB

Open AccessFeature PaperArticle

Active Ag-, Fe-, and AC-Modified TiO₂ Mesoporous Photocatalysts for Anionic and Cationic Dye Degradation

by Daniela Negoescu, Irina Atkinson, Mihaela Gherendi, Daniela C. Culita, Adriana Baran, Simona Petrescu, Veronica Bratan and Viorica Parvulescu

Catalysts 2025, 15(5), 479; https://doi.org/10.3390/catal15050479 - 13 May 2025

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Abstract

TiO₂ mesoporous supports were obtained by the sol–gel method from different precursors (titaniumethoxide, isopropoxide, or butoxide) in the presence of nonionic, cationic, and anionic surfactants. Among these samples, those obtained from Ti isopropoxide, Brij58 w/o activated carbon (AC), were selected as supports. [...] Read more.

TiO₂ mesoporous supports were obtained by the sol–gel method from different precursors (titaniumethoxide, isopropoxide, or butoxide) in the presence of nonionic, cationic, and anionic surfactants. Among these samples, those obtained from Ti isopropoxide, Brij58 w/o activated carbon (AC), were selected as supports. Photocatalysts were obtained by modifying these supports with Ag, Fe, and AgFe (each metal around 1% mass). The characterization results showed a stronger influence of titania precursors, surfactants, and AC on the texture and an insignificant effect on the crystalline structure and morphology of the obtained materials. X-ray photoelectron spectroscopy revealed the effects of AC and Fe on the Ag⁰ concentration and of Ag on Fe-reduced species. Based on this information, the results obtained by H₂-TPR, UV–Vis, Raman, and photoluminescence spectroscopy were explained. The performance of the photocatalysts was evaluated in the degradation of Congo Red (CR) and Crystal Violet (CV) dyes under UV and visible light. The Ag-TiO₂ sample exhibited the best activity in degrading CR at acidic pH and in degrading CV under basic conditions. In visible light, we observed the significant effects of the surface plasmon resonance, AC, Ag, and Fe on the activity in CR photodegradation. The proposed kinetics and mechanisms complete the study of the reactions. Full article

(This article belongs to the Special Issue Effect of the Modification of Catalysts on the Catalytic Performance, 2nd Edition)

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15 pages, 4407 KiB

Open AccessArticle

Sustainable Hydrogen from Methanol: NiCuCe Catalyst Design with CO₂-Driven Regeneration for Carbon-Neutral Energy Systems

by Yankun Jiang, Liangdong Zhao and Siqi Li

Catalysts 2025, 15(5), 478; https://doi.org/10.3390/catal15050478 - 13 May 2025

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Abstract

This study addresses energy transition challenges through the development of NiCuCe catalysts for high-purity hydrogen production via methanol decomposition, with carbon deposition issues mitigated by CO₂-assisted regeneration. As fossil fuel depletion advances and the urgency of climate change increases, methanol-derived hydrogen [...] Read more.

This study addresses energy transition challenges through the development of NiCuCe catalysts for high-purity hydrogen production via methanol decomposition, with carbon deposition issues mitigated by CO₂-assisted regeneration. As fossil fuel depletion advances and the urgency of climate change increases, methanol-derived hydrogen (CH₃OH → CO + 2H₂) emerges as a carbon-neutral alternative to conventional fossil fuel-based energy systems. The catalyst’s dual Cu²⁺/Ni²⁺ active sites facilitate selective C–O bond cleavage, achieving more than 80% methanol conversion at temperatures exceeding 280 °C without the need for fossil methane inputs. Crucially, CO₂ gasification enables catalyst regeneration through the conversion of 90% carbon deposits into reusable media, circumventing energy-intensive combustion processes. This dual-function system couples carbon capture to hydrogen infrastructure, thereby stabilizing production while valorizing waste CO₂. This innovation minimizes reliance on rare metals through efficient regeneration cycles, mitigating resource constraints during energy crises. Full article

(This article belongs to the Special Issue Catalytic Gasification)

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45 pages, 19249 KiB

Open AccessFeature PaperReview

Multidimensional Engineering of Nanoconfined Catalysis: Frontiers in Carbon-Based Energy Conversion and Utilization

by Qimin Fang, Qihan Sun, Jinming Ge, Haiwang Wang and Jian Qi

Catalysts 2025, 15(5), 477; https://doi.org/10.3390/catal15050477 - 12 May 2025

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Abstract

Amid global efforts toward carbon neutrality, nanoconfined catalysis has emerged as a transformative strategy to address energy transition challenges through precise regulation of catalytic microenvironments. This review systematically examines recent advancements in nanoconfined catalytic systems for carbon-based energy conversion (CO₂, CH [...] Read more.

Amid global efforts toward carbon neutrality, nanoconfined catalysis has emerged as a transformative strategy to address energy transition challenges through precise regulation of catalytic microenvironments. This review systematically examines recent advancements in nanoconfined catalytic systems for carbon-based energy conversion (CO₂, CH₄, etc.), highlighting their unique capability to modulate electronic structures and reaction pathways via quantum confinement and interfacial effects. By categorizing their architectures into dimension-oriented frameworks (1D nanotube channels, 2D layered interfaces, 3D core-shell structures, and heterointerfaces), we reveal how geometric constraints synergize with mass/electron transfer dynamics to enhance selectivity and stability. Critical optimization strategies—including heteroatom doping to optimize active site coordination, defect engineering to lower energy barriers, and surface modification to tailor local microenvironments—are analyzed to elucidate their roles in stabilizing metastable intermediates and suppressing catalyst deactivation. We further emphasize the integration of machine learning, in situ characterization, and modular design as essential pathways to establish structure–activity correlations and accelerate industrial implementation. This work provides a multidimensional perspective bridging fundamental mechanisms with practical applications to advance carbon-neutral energy systems. Full article

(This article belongs to the Collection Catalytic Conversion and Utilization of Carbon-Based Energy)

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26 pages, 5961 KiB

Open AccessArticle

Structural Features Underlying the Mismatch Between Catalytic and Cytostatic Properties in L-Asparaginase from Rhodospirillum rubrum

by Igor D. Zlotnikov, Anastasia N. Shishparyonok, Marina V. Pokrovskaya, Svetlana S. Alexandrova, Dmitry D. Zhdanov and Elena V. Kudryashova

Catalysts 2025, 15(5), 476; https://doi.org/10.3390/catal15050476 - 12 May 2025

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Abstract

The underlying structural features of the mismatch between catalytic and cytostatic properties in L-asparaginase from Rhodospirillum rubrum (RrA) and three of its mutants were investigated. The rationale for selecting the specific mutations (RrA_{A64V, E67K}; RrA_{R118H, G120R}; RrA_{E149R, V150P,} [...] Read more.

The underlying structural features of the mismatch between catalytic and cytostatic properties in L-asparaginase from Rhodospirillum rubrum (RrA) and three of its mutants were investigated. The rationale for selecting the specific mutations (RrA_{A64V, E67K}; RrA_{R118H, G120R}; RrA_{E149R, V150P, F151T}) is to elucidate the role of inter-subunit interaction in RrA and its impact on catalytic efficiency and stability. Bioinformatic modeling revealed a predominantly negative surface charge on RrA with limited positive charge clusters in the vicinity of the interface region. Thus, some negatively charged groups were replaced with positively charged ones to enhance the electrostatic interactions and stabilize the enzyme quaternary structure. RrA_{A64V, E67K} and RrA_{R118H, G120R} additionally contained an N-terminal 17-amino acid capsid peptide derived from the bacteriophage T7 (MASMTGGQQMGRGSSRQ), which could potentially affect the conformational stability of theenzymes. Circular dichroism (CD) spectroscopy was applied to the kinetic parameters analysis of Asn hydrolysis and showed that native RrA displayed a V_max of 30 U/mg and a K_M of 4.5 ± 0.5 mM. RrA_{E149R, V150P, and F151T} exhibited a substantially increased V_max of 57 U/mg. The catalytic efficiency of V_max/K_M also improved compared to the native enzyme: the V_max/K_M increased from approximately 7 U/mg × mM⁻¹ (for the native enzyme) to 9 U/mg × mM⁻¹ for Mut3. Other mutants exhibited less pronounced changes. Thermo-denaturation studies allowed us to determine the phase transition parameters of the RrA variants in comparison with commercial reference sample EcA. RrA_{A64V, E67K} and RrA_{R118H, G120R} exhibited the most favorable phase transition parameters, with melting temperatures (T_m) of 60.3 °C and 59.4 °C, respectively, exceeding that of the wild-type RrA (54.6 °C) and RrA_{E149R, V150P, F151T} (52 °C). The EcA demonstrated a slightly superior thermal stability, with a T_m of 62 °C. The mutations showed a significant effect on protein stability during trypsinolysis. Therefore, RrA_{E149R, V150P, F151T} showed higher resistance (45% activity remaining after 30 min of trypsin exposure) compared to the native RrA retained 20% activity. EcA preparations exhibited lower stability to trypsinolysis (losing over 90% activity in 15 min). The cytostatic effects were evaluated using MTT assays against K562 (leukemic) and A549 (lung carcinoma) cell lines. The MTT assays with K562 cells revealed that RrA_{E149R, V150P, F151T} (IC₅₀ of 10 U/mL) and RrA_{R118H, G120R} (IC₅₀ of 11.5 U/mL) exhibited superior antiproliferative activity compared to native enzymes RrA (IC₅₀ of 15 U/mL) and EcA (24 U/mL). RrA_{E149R, V150P, F151T} showed the most significant improvement in cytostatic activity. The results obtained indicate that the substitutions in RrA_{E149R, V150P, F151T} resulted in the improvement of the enzyme biocatalytic properties and an increase in the resistance to aggregation and trypsinolysis. This highlights the role of electrostatic interactions in stabilizing the oligomeric structure of the enzyme, which eventually translates into an improvement in cytostatic efficiency and antiproliferative forces. Full article

(This article belongs to the Section Biocatalysis)

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18 pages, 3933 KiB

Open AccessArticle

Ru Nanoparticle Assemblies Modified with Single Mo Atoms for Hydrogen Evolution Reactions in Seawater Electrocatalysis

by Shuhan Wang, Jiani Qin, Yong Zhang, Shuai Chen, Wenjun Yan, Haiqing Zhou and Xiujun Fan

Catalysts 2025, 15(5), 475; https://doi.org/10.3390/catal15050475 - 12 May 2025

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Abstract

Ru-based catalysts manifest unparalleled hydrogen evolution reaction (HER) performance, but the hydrolysis of Ru species and the accumulation of corresponding reaction intermediates greatly limit HER activity and stability. Herein, Ru nanoparticle assemblies modified with single Mo atoms and supported on N-incorporated graphene (referred [...] Read more.

Ru-based catalysts manifest unparalleled hydrogen evolution reaction (HER) performance, but the hydrolysis of Ru species and the accumulation of corresponding reaction intermediates greatly limit HER activity and stability. Herein, Ru nanoparticle assemblies modified with single Mo atoms and supported on N-incorporated graphene (referred to as MoRu-NG) are compounded via hydrothermal and chemical vapor deposition (CVD) methods. The incorporation of single Mo atoms into Ru lattices modifies the local atomic milieu around Ru centers, significantly improving HER catalytic behavior and stability. More specifically, MoRu-NG achieves overpotentials of 53 mV and 28 mV at 10 mA cm⁻², with exceptional stability in acidic and alkaline seawater solutions, respectively. In MoRu-NG, Ru atoms have a special electronic structure and thus possess optimal hydrogen adsorption energy, which indicates that excellent HER activity mainly hinges upon Ru centers. To be specific, the d-electron orbitals of Ru atoms are close to half full, giving Ru atoms moderate bond energy for the assimilation and release of hydrogen, which is beneficial for the conversion of reaction intermediates. Moreover, the incorporation of single Mo atoms facilitates the formation of O and O’-bidentate ligands, significantly enhancing the structural stability of MoRu-NG in universal-pH seawater electrolysis. This work advances a feasible construction method of hexagonal octahedral configuration (Ru-O-Mo-N-C) and provides a route to synthesize an efficient and stable catalyst for electrocatalytic HER in universal-pH seawater. Full article

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