Catalysts

21 pages, 1562 KiB

Open AccessArticle

Application of Fused Filament Fabrication in Preparation of Ceramic Monolithic Catalysts for Oxidation of Gaseous Mixture of Volatile Aromatic Compounds

by Filip Car, Dominik Horvatić, Vesna Tomašić, Domagoj Vrsaljko and Zoran Gomzi

Catalysts 2025, 15(7), 677; https://doi.org/10.3390/catal15070677 - 11 Jul 2025

Abstract

The aim of this work was the preparation of ceramic monolithic catalysts for the catalytic oxidation of gaseous mixture of benzene, toluene, ethylbenzene and o-xylene BTEX. The possibility of using zirconium dioxide (ZrO₂) as a filament for the fabrication of 3D-printed [...] Read more.

The aim of this work was the preparation of ceramic monolithic catalysts for the catalytic oxidation of gaseous mixture of benzene, toluene, ethylbenzene and o-xylene BTEX. The possibility of using zirconium dioxide (ZrO₂) as a filament for the fabrication of 3D-printed ceramic monolithic carriers was investigated using fused filament fabrication. A mixed manganese and iron oxide, MnFeO_x, was used as the catalytically active layer, which was applied to the monolithic substrate by wet impregnation. The approximate geometric surface area of the obtained carrier was determined to be 53.4 cm², while the mass of the applied catalytically active layer was 50.3 mg. The activity of the prepared monolithic catalysts for the oxidation of BTEX was tested at different temperatures and space times. The results obtained were compared with those obtained with commercial monolithic catalysts made of ceramic cordierite with different channel dimensions, and with monolithic catalysts prepared by stereolithography. In the last part of the work, a kinetic analysis and the modeling of the monolithic reactor were carried out, comparing the experimental results with the theoretical results obtained with the 1D pseudo-homogeneous and 1D heterogeneous models. Although both models could describe the investigated experimental system very well, the 1D heterogeneous model is preferable, as it takes into account the heterogeneity of the reaction system and therefore provides a more realistic description. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

19 pages, 1163 KiB

Open AccessArticle

Regulation of Ag₁Cu_x/SBA-15 Catalyst for Efficient CO Catalytic Degradation at Room Temperature

by Fukun Bi, Haotian Hu, Ye Zheng, Yanxuan Wang, Yuxin Wang, Baolin Liu, Han Dong and Xiaodong Zhang

Catalysts 2025, 15(7), 676; https://doi.org/10.3390/catal15070676 - 11 Jul 2025

Abstract

The regulation of the active sites of a catalyst is important for its application. Herein, a series of Ag₁Cu_x/SBA-15 catalysts with different molar ratios of Ag to Cu were synthesized via the impregnation method, and the active sites of [...] Read more.

The regulation of the active sites of a catalyst is important for its application. Herein, a series of Ag₁Cu_x/SBA-15 catalysts with different molar ratios of Ag to Cu were synthesized via the impregnation method, and the active sites of Ag₁Cu_x were regulated via various pretreatment conditions. These as-prepared Ag₁Cu_x/SBA-15 catalysts were characterized by many technologies, and their catalytic performance was estimated through CO catalytic oxidation. Among these catalysts, Ag₁Cu_0.025/SBA-15, with a Ag/Cu molar ratio of 1:0.025 and pretreated under the condition of 500 °C O₂/Ar for 2 h, followed by 300 °C H₂ for another 2 h, presented optimal CO degradation performance, which could realize the oxidation of 98% CO at 34 °C (T₉₈ = 34 °C). Meanwhile, Ag₁Cu_0.025/SBA-15 also displayed great reusability. Characterization results, such as X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectra (UV-vis DRS), temperature-programmed H₂ reduction (H₂-TPR), and physical adsorption, suggested that the optimal catalytic performance of Ag₁Cu_0.025/SBA-15 was ascribed to its high interspersion of Ag nanoparticles, better low-temperature reduction ability, the interaction between Ag and Cu, and its high surface area and large pore volume. This study provides guidance for the regulation of active sites for low-temperature catalytic degradation. Full article

(This article belongs to the Special Issue Zeolites as Catalysts: Applications in Chemical Engineering, Energy Sources and Environmental Protection, 2nd Edition)

30 pages, 2208 KiB

Open AccessArticle

Production of Sustainable Synthetic Natural Gas from Carbon Dioxide and Renewable Energy Catalyzed by Carbon-Nanotube-Supported Ni and ZrO₂ Nanoparticles

by João Pedro Bueno de Oliveira, Mariana Tiemi Iwasaki, Henrique Carvalhais Milanezi, João Lucas Marques Barros, Arnaldo Agostinho Simionato, Bruno da Silva Marques, Carlos Alberto Franchini, Ernesto Antonio Urquieta-González, Ricardo José Chimentão, José Maria Corrêa Bueno, Adriana Maria da Silva and João Batista Oliveira dos Santos

Catalysts 2025, 15(7), 675; https://doi.org/10.3390/catal15070675 - 11 Jul 2025

Abstract

The production of synthetic natural gas in the context of power-to-gas is a promising technology for the utilization of CO₂. Ni-based catalysts supported on carbon nanotubes (CNTs) were prepared through incipient wetness impregnation and characterized using N₂ adsorption, X-ray diffraction [...] Read more.

The production of synthetic natural gas in the context of power-to-gas is a promising technology for the utilization of CO₂. Ni-based catalysts supported on carbon nanotubes (CNTs) were prepared through incipient wetness impregnation and characterized using N₂ adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and temperature-programmed reduction (TPR). The catalysts were tested for CO₂ methanation in the 200–400 °C temperature range and at atmospheric pressure. The results demonstrated that the catalytic activity increased with the addition of the CNTs and Ni loading. The selectivity towards CH₄ was close to 100% for the Ni/ZrO₂/CNT catalysts. Reduction of the calcined catalyst at 500 °C using H₂ modified the surface chemistry of the catalyst, leading to an increase in the Ni particles. The CO₂ conversion was dependent on the Ni loading and the temperature reduction in the NiO species. The 10Ni/ZrO₂/CNT catalyst was highly stable in CO₂ methanation at 350 °C for 24 h. Thus, CNTs combined with Ni and ZrO₂ were considered promising for use as catalysts in CO₂ methanation at low temperatures. Full article

(This article belongs to the Special Issue Sustainable Catalytic Routes for the Production of Green Synthetic Fuels and Other Value-Added Products)

20 pages, 4894 KiB

Open AccessArticle

Ag-Cu Synergism-Driven Oxygen Structure Modulation Promotes Low-Temperature NO_x and CO Abatement

by Ruoxin Li, Jiuhong Wei, Bin Jia, Jun Liu, Xiaoqing Liu, Ying Wang, Yuqiong Zhao, Guoqiang Li and Guojie Zhang

Catalysts 2025, 15(7), 674; https://doi.org/10.3390/catal15070674 - 11 Jul 2025

Abstract

The efficient simultaneous removal of NO_x and CO from sintering flue gas under low-temperature conditions (110–180 °C) in iron and steel enterprises remains a significant challenge in the field of environmental catalysis. In this study, we present an innovative strategy to enhance [...] Read more.

The efficient simultaneous removal of NO_x and CO from sintering flue gas under low-temperature conditions (110–180 °C) in iron and steel enterprises remains a significant challenge in the field of environmental catalysis. In this study, we present an innovative strategy to enhance the performance of CuSmTi catalysts through silver modification, yielding a bifunctional system capable of oxygen structure regulation and demonstrating superior activity for the combined NH₃-SCR and CO oxidation reactions under low-temperature, oxygen-rich conditions. The modified AgCuSmTi catalyst achieves complete NO conversion at 150 °C, representing a 50 °C reduction compared to the unmodified CuSmTi catalyst (T_100% = 200 °C). Moreover, the catalyst exhibits over 90% N₂ selectivity across a broad temperature range of 150–300 °C, while achieving full CO oxidation at 175 °C. A series of characterization techniques, including XRD, Raman spectroscopy, N₂ adsorption, XPS, and O₂-TPD, were employed to elucidate the Ag-Cu interaction. These modifications effectively optimize the surface physical structure, modulate the distribution of acid sites, increase the proportion of Lewis acid sites, and enhance the activity of lattice oxygen species. As a result, they effectively promote the adsorption and activation of reactants, as well as electron transfer between active species, thereby significantly enhancing the low-temperature performance of the catalyst. Furthermore, in situ DRIFTS investigations reveal the reaction mechanisms involved in NH₃-SCR and CO oxidation over the Ag-modified CuSmTi catalyst. The NH₃-SCR process predominantly follows the L-H mechanism, with partial contribution from the E-R mechanism, whereas CO oxidation proceeds via the MvK mechanism. This work demonstrates that Ag modification is an effective approach for enhancing the low-temperature performance of CuSmTi-based catalysts, offering a promising technical solution for the simultaneous control of NO_x and CO emissions in industrial flue gases. Full article

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

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25 pages, 6054 KiB

Open AccessReview

Recent Advances in Biocatalytic Dearomative Spirocyclization Reactions

by Xiaorui Chen, Changtong Zhu, Luyun Ji, Changmei Liu, Yan Zhang, Yijian Rao and Zhenbo Yuan

Catalysts 2025, 15(7), 673; https://doi.org/10.3390/catal15070673 - 10 Jul 2025

Abstract

Spirocyclic architectures, which feature two rings sharing a single atom, are common in natural products and exhibit beneficial biological and material properties. Due to the significance of these architectures, biocatalytic dearomative spirocyclization has recently emerged as a powerful approach for constructing three-dimensional spirocyclic [...] Read more.

Spirocyclic architectures, which feature two rings sharing a single atom, are common in natural products and exhibit beneficial biological and material properties. Due to the significance of these architectures, biocatalytic dearomative spirocyclization has recently emerged as a powerful approach for constructing three-dimensional spirocyclic frameworks under mild, sustainable conditions and with exquisite stereocontrol. This review surveys the latest advances in biocatalyzed spirocyclization of all-carbon arenes (phenols and benzenes), aza-aromatics (indoles and pyrroles), and oxa-aromatics (furans). We highlight cytochrome P450s, flavin-dependent monooxygenases, multicopper oxidases, and novel metalloenzyme platforms that effect regio- and stereoselective oxidative coupling, epoxidation/semi-pinacol rearrangement, and radical-mediated cyclization to produce diverse spirocycles. Mechanistic insights gleaned from structural, computational, and isotope-labeling studies are discussed where necessary to help the readers further understand the reported reactions. Collectively, these examples demonstrate the transformative potential of biocatalysis to streamline access to spirocyclic scaffolds that are challenging to prepare through traditional methods, underscoring biocatalysis as a transformative tool for synthesizing pharmaceutically relevant spiroscaffolds while adhering to green chemistry paradigms to ultimately contribute to a cleaner and more sustainable future. Full article

(This article belongs to the Section Biocatalysis)

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18 pages, 4550 KiB

Open AccessArticle

Efficient Visible-Light-Driven Photocatalysis of BiVO₄@Diatomite for Degradation of Methoxychlor

by Nazar Iqbal, Xiaocui Huang, Khalid Mohamedali Hamid, Hongming Yuan, Irum Batool and Yuxiang Yang

Catalysts 2025, 15(7), 672; https://doi.org/10.3390/catal15070672 - 10 Jul 2025

Abstract

As a persistent organic pollutant, methoxychlor has drawn considerable environmental attention. Photocatalysis, recognized for its environmentally friendly characteristics, has been widely utilized for the degradation of contaminants. In this study, the photocatalytic material BiVO₄@diatomite was successfully synthesized via the liquid-phase precipitation [...] Read more.

As a persistent organic pollutant, methoxychlor has drawn considerable environmental attention. Photocatalysis, recognized for its environmentally friendly characteristics, has been widely utilized for the degradation of contaminants. In this study, the photocatalytic material BiVO₄@diatomite was successfully synthesized via the liquid-phase precipitation method. The synthesized material was comprehensively characterized using X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectroscopy (DRS), and a Brunauer–Emmett–Teller (BET) analysis, providing robust evidence for the material’s stability and biocompatibility. The results confirmed the successful deposition of BiVO₄ onto the diatomite surface. Furthermore, the effects of various parameters, including the initial methoxychlor concentration, pH, light exposure duration, and illumination intensity, on the photocatalytic degradation efficiency of methoxychlor by BiVO₄@diatomite were systematically investigated to optimize degradation performance. The identification of optimal reaction conditions and the proposed degradation mechanism based on experimental findings will be valuable for guiding future studies and practical applications in environmental pollution control. The integration of BiVO₄ with diatomite in this study yields a novel composite system with significantly enhanced photocatalytic degradation performance, offering fresh insights into the design of efficient, stable, and eco-friendly materials for pollutant removal. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysis and Sustainable Technologies for Water Purification)

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22 pages, 6102 KiB

Open AccessFeature PaperReview

Current Developments in Ozone Catalyst Preparation Techniques and Their Catalytic Oxidation Performance

by Jiajia Gao, Siqi Chen, Yun Gao, Wenquan Sun, Jun Zhou, Kinjal J. Shah and Yongjun Sun

Catalysts 2025, 15(7), 671; https://doi.org/10.3390/catal15070671 - 10 Jul 2025

Abstract

Through the use of heterogeneous catalysts, catalytic ozone oxidation technology, an effective and eco-friendly advanced oxidation process (AOP), facilitates the breakdown of ozone into reactive oxygen species (like ·OH) and greatly increases the mineralization efficiency of pollutants. This study examines the development of [...] Read more.

Through the use of heterogeneous catalysts, catalytic ozone oxidation technology, an effective and eco-friendly advanced oxidation process (AOP), facilitates the breakdown of ozone into reactive oxygen species (like ·OH) and greatly increases the mineralization efficiency of pollutants. This study examines the development of heterogeneous ozone catalysts through a critical evaluation of the five primary preparation techniques: ion exchange, sol–gel, coprecipitation, impregnation, and hydrothermal synthesis. Each preparation method’s inherent qualities, benefits, drawbacks, and performance variations are methodically investigated, with an emphasis on how they affect the breakdown of different resistant organic compounds. Even though heterogeneous catalysts are more stable and reusable than homogeneous catalysts, they continue to face issues like active component leaching, restricted mass transfer, and ambiguous mechanisms. In order to determine the key paths for catalyst selection in catalytic ozone treatment going forward, the main goal of this review is to provide an overview of the accomplishments in the field of the heterogeneous ozone catalyst treatment of wastewater that is difficult to degrade. Full article

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

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22 pages, 8848 KiB

Open AccessFeature PaperReview

Sustainable Treatment of Plastic Wastes with Photocatalytic Technologies: A Review

by Xin Wang, Xiaoling Ye, Duqiang Zhang, Bingxu Zhang, Huimei Liu and Wenbin Qu

Catalysts 2025, 15(7), 670; https://doi.org/10.3390/catal15070670 - 10 Jul 2025

Abstract

Plastic waste pollution has been widely recognized as one of the most severe and pressing environmental challenges of our time, posing significant threats to ecosystem stability and human health. The transformation of plastic waste into high-value chemicals and clean energy via photocatalytic reforming [...] Read more.

Plastic waste pollution has been widely recognized as one of the most severe and pressing environmental challenges of our time, posing significant threats to ecosystem stability and human health. The transformation of plastic waste into high-value chemicals and clean energy via photocatalytic reforming technology is increasingly regarded as a promising and sustainable alternative pathway, offering dual benefits of resource recovery and environmental remediation. This review first provides an overview of the current state of research on plastic waste management. It then systematically summarizes recent representative advances in the coupling of plastic upcycling with photocatalytic technologies, with a particular focus on the potential of plastics as carbon sources in both photodegradation and photosynthetic transformation pathways, highlighting their value and future prospects. Finally, this review outlines the key scientific challenges that urgently need to be addressed in the field of photocatalytic conversion of plastic waste, and, in light of emerging research trends, proposes several promising directions for future investigation along with the authors’ perspectives. It is hoped that these insights will provide useful guidance and inspiration for the continued advancement of this field. Full article

(This article belongs to the Special Issue Advances in Catalytic Processes for Carbon Neutralization)

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21 pages, 3111 KiB

Open AccessArticle

Iron Sludge-Derived Photo-Fenton Reaction for Laundry Wastewater Effluent Oxidation and Process Optimization into Industrial Ecology Symbiosis

by Amira Ben Gouider Trabelsi, Fatemah H. Alkallas, Shehab A. Mansour, Abdullah F. Al Naim, Adil Alshoaibi, Najeh Rekik, Manasik M. Nour and Maha A. Tony

Catalysts 2025, 15(7), 669; https://doi.org/10.3390/catal15070669 - 10 Jul 2025

Abstract

Controlled iron extraction from iron-based sludge (Fe-Sludge) drainage and its use as a Fenton’s reagent is investigated in the current study for eliminating organics from launderette discharge stream. The influences of the iron dosage, hydrogen peroxide concentration, and pH are assessed [...] Read more.

Controlled iron extraction from iron-based sludge (Fe-Sludge) drainage and its use as a Fenton’s reagent is investigated in the current study for eliminating organics from launderette discharge stream. The influences of the iron dosage, hydrogen peroxide concentration, and pH are assessed as treatment factors for their direct impact on the oxidation of organic compounds. Additionally, optimal oxidation conditions are determined using the response surface methodology (RSM) technique, and the ranges of treatment variables are analyzed. The optimum values of a pH of 2.0, Fe sludge concentration of 99 mg/L, and H₂O₂ content of 402 mg/L resulted in optimal organics removal of up to 98%, expressed as Chemical Oxygen Demand (COD) removal. The oxidation efficacy attained from the design is confirmed and the model validation is assessed, and the suggestive model is accepted since it possesses a correlation coefficient of 97.7%. The thermodynamic and kinetic models are also investigated, and the reaction showed that the temperature increases resulted in the oxidation efficiency being reduced. The oxidation efficiency expressed as COD reduction is clearly characterized by first-order reaction kinetics. The thermodynamic characteristics indicated that the oxidation reaction was exothermic and not spontaneous. Full article

(This article belongs to the Special Issue Advanced Catalytic Processes for Wastewater Treatment)

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31 pages, 8391 KiB

Open AccessFeature PaperReview

Recent Advances in Catalyst Innovation, Mechanism Exploration, and Process Optimization for Synthesis of Glycerol Carbonate

by Honglei Sun, Zhenyu Lei, Jinghui Shi and Mingjun Jia

Catalysts 2025, 15(7), 668; https://doi.org/10.3390/catal15070668 - 9 Jul 2025

Viewed by 55

Abstract

The catalytic conversion of bio-based glycerol (Gly) into high-value glycerol carbonate (GC) has received great attention from both the academic and industrial fields. The development of highly efficient catalysts and economical industrial processes remains a challenging subject. In this mini-review, we summary the [...] Read more.

The catalytic conversion of bio-based glycerol (Gly) into high-value glycerol carbonate (GC) has received great attention from both the academic and industrial fields. The development of highly efficient catalysts and economical industrial processes remains a challenging subject. In this mini-review, we summary the recent advances in catalyst design, characterization, mechanism, and catalytic process optimization, including the various synthetic strategies of GC, such as the coupling of CO₂ and Gly or its derivatives like glycidol (GD), the transesterification of Gly with small carbonate-containing molecules, and the carbonylation of Gly with urea. The main difficulties and challenges faced by constructing high-performance catalysts and achieving scale production of GC have been put forward, and the future research directions and opportunities in catalyst innovation, reaction mechanism exploration, and continuous catalytic process improvement have also been suggested. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Biomass and Its Derivatives into Chemicals)

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14 pages, 935 KiB

Open AccessArticle

Plasmon-Driven Catalytic Inhibition of pATP Oxidation as a Mechanism for Indirect Fe²⁺ Detection on a SERS-Active Platform

by Alexandru-Milentie Hada, Mihail-Mihnea Moruz, Alexandru Holca, Simion Astilean, Marc Lamy de la Chapelle and Monica Focsan

Catalysts 2025, 15(7), 667; https://doi.org/10.3390/catal15070667 - 8 Jul 2025

Viewed by 222

Abstract

The detection of Fe²⁺ in environmental water sources is critical due to its biological relevance and potential toxicity at elevated levels. Herein, we report a plasmon-driven catalytic sensing nanoplatform based on p-aminothiophenol (pATP)-functionalized silver nanoparticles (AgNPs) for the selective and sensitive detection [...] Read more.

The detection of Fe²⁺ in environmental water sources is critical due to its biological relevance and potential toxicity at elevated levels. Herein, we report a plasmon-driven catalytic sensing nanoplatform based on p-aminothiophenol (pATP)-functionalized silver nanoparticles (AgNPs) for the selective and sensitive detection of Fe²⁺. The nanoplatform exploits the inhibition of the plasmon-driven catalytic conversion of pATP to 4,4-dimercaptoazobenzene (DMAB), monitored via surface-enhanced Raman scattering (SERS) spectroscopy. The catalytic efficiency was quantified by the intensity ratio between the formed DMAB-specific Raman band and the common aromatic ring vibration band of pATP and DMAB. This ratio decreased proportionally with increasing Fe²⁺ concentration over a range of 100 µM to 1.5 mM, with a calculated limit of detection of 39.7 µM. High selectivity was demonstrated against common metal ions, and excellent recovery rates (96.6–99.4%) were obtained in real water samples. Mechanistic insights, supported by chronopotentiometric measurements under light irradiation, revealed a competitive oxidation pathway in which Fe²⁺ preferentially consumes plasmon-generated hot holes over pATP. This mechanism clarifies the observed catalytic inhibition and supports the design of redox-responsive SERS sensors. The platform offers a rapid, low-cost, and portable solution for Fe²⁺ monitoring and holds promise for broader applications in detecting other redox-active analytes in complex environmental matrices. Full article

(This article belongs to the Special Issue Innovative Catalytic and Photocatalytic Systems for Environmental Remediation, 2nd Edition)

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19 pages, 8425 KiB

Open AccessArticle

Efficiency of the Electrocatalytic Nitrate Reduction to Ammonia: Do the Surface Nanostructures Play an Essential Role?

by Olga Lebedeva, Irina Kuznetsova, Dmitry Kultin, Alexander Leonov, Maxim Zakharov, Alexander Kustov, Stanislav Dvoryak and Leonid Kustov

Catalysts 2025, 15(7), 666; https://doi.org/10.3390/catal15070666 - 8 Jul 2025

Viewed by 160

Abstract

The degradation of electrochemical materials during energy conversion and storage, in particular the electrocatalyst materials, is becoming increasingly important. The selection and design of sustainable materials is an important task. This work examines the synthesis, characterization, and application of an electrocatalyst (based on [...] Read more.

The degradation of electrochemical materials during energy conversion and storage, in particular the electrocatalyst materials, is becoming increasingly important. The selection and design of sustainable materials is an important task. This work examines the synthesis, characterization, and application of an electrocatalyst (based on an amorphous alloy Co75Si15Fe5Cr4.5) having a structured surface in the form of nanocells for a “green” nitrate reduction reaction (NO₃RR), which can serve as an alternative to the well-known Haber-Bosch process for the synthesis of ammonia. The material for the electrocatalyst was obtained by anodizing the alloy in the ionic liquid BmimNTf₂ and characterized by using a combination of modern physicochemical and electrochemical methods. The Faradaic efficiency (FE) for the nanocell catalyst exceeds by more than three-fold and seven-fold catalyst with a polished surface and the initial catalyst having a natural oxide on the surface, respectively. A mechanism of this reaction on the studied electrocatalysts with structured and non-structured surfaces is proposed. It is mentioned that the nanocell electrocatalyst is an extremely stable material that passes all tests without visible changes. The authors consider their work as a starting point for the application of a nanostructured Co-electrocatalyst in NO₃RR. Full article

(This article belongs to the Special Issue Photocatalyzed and Electrochemical Processes for a Cleaner Environment)

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46 pages, 3942 KiB

Open AccessReview

Catalytic Fluorination with Modern Fluorinating Agents: Recent Developments and Synthetic Scope

by Muhammad Saeed Akhtar, Mohammad Aslam, Wajid Zaman, Kuppu Sakthi Velu, Seho Sun and Hee Nam Lim

Catalysts 2025, 15(7), 665; https://doi.org/10.3390/catal15070665 - 8 Jul 2025

Viewed by 353

Abstract

Fluorinated organic molecules have become indispensable in modern chemistry, owing to the unique properties imparted by fluorine to other compounds, including enhanced metabolic stability, controlled lipophilicity, and improved bioavailability. The site-selective incorporation of fluorine atoms into organic frameworks is essential in pharmaceutical, agrochemical, [...] Read more.

Fluorinated organic molecules have become indispensable in modern chemistry, owing to the unique properties imparted by fluorine to other compounds, including enhanced metabolic stability, controlled lipophilicity, and improved bioavailability. The site-selective incorporation of fluorine atoms into organic frameworks is essential in pharmaceutical, agrochemical, and material science research. In recent years, catalytic fluorination has become an important methodology for the efficient and selective incorporation of fluorine atoms into complex molecular architectures. This review highlights advances in catalytic fluorination reactions over the past six years and describes the contributions of transition metal catalysts, photocatalysts, organocatalysts, and electrochemical systems that have enabled site-selective fluorination under a variety of conditions. Particular attention is given to the use of well-defined fluorinating agents, including Selectfluor, N-fluorobenzenesulfonimide (NFSI), AlkylFluor, Synfluor, and hypervalent iodine reagents. These reagents have been combined with diverse catalytic systems, such as AgNO₃, Rh(II), Mo-based complexes, Co(II)-salen, and various organocatalysts, including β,β-diaryl serine catalysts, isothiourea catalysts, and chiral phase-transfer catalysts. This review summarizes proposed mechanisms reported in the original studies and discusses examples of electrophilic, nucleophilic, radical, photoredox, and electrochemical fluorination pathways. Recent developments in stereoselective and more sustainable protocols are also examined. By consolidating these strategies, this article provides an up-to-date perspective on catalytic fluorination and its impact on synthetic organic chemistry. Full article

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

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14 pages, 3884 KiB

Open AccessArticle

Self-Supported Tailoring of Nickel Sulfide/CuCo Nanosheets into Hierarchical Heterostructures for Boosting Urea Oxidation Reaction

by Prince J. J. Sagayaraj, Aravind Senthilkumar, Juwon Lee, Eun-Kyeong Byeon, Hyoung-il Kim, Sulakshana Shenoy and Karthikeyan Sekar

Catalysts 2025, 15(7), 664; https://doi.org/10.3390/catal15070664 - 7 Jul 2025

Viewed by 253

Abstract

Electro-oxidation of urea (UOR) in alkaline medium is one of the most effective alternative ways of producing green hydrogen, as the oxidation potential in UOR is less and thermodynamically more favorable than conventional water oxidation. The development of cost-effective materials in catalyzing UOR [...] Read more.

Electro-oxidation of urea (UOR) in alkaline medium is one of the most effective alternative ways of producing green hydrogen, as the oxidation potential in UOR is less and thermodynamically more favorable than conventional water oxidation. The development of cost-effective materials in catalyzing UOR is recently seeking more attention in the research hotspot. Suitably modifying the Ni-based catalysts towards active site creation and preventing surface passivation is much important in this context, following which we reported the synthesis of Ni₃S₂ (NS) supported with CuCo (CC) bimetallic (NSCC). A simple hydrothermal route for NS synthesis and the electrodeposition method for CuCo (CC) deposition is adapted in a self-supported manner. The NS and CC catalysts exhibited sheet-like morphology, as confirmed by SEM and TEM analysis. The bimetallic CC deposition prevented the surface passivation of nickel sulfide (NS) over oxygen evolution reaction (OER) and improved the charge-transfer kinetics. The NSCC catalyst catalyzed UOR in an alkaline medium, which required a lower potential of 1.335 V vs. RHE to attain the current density of 10 mAcm⁻², with a lower Tafel slope value of 131 mVdec⁻¹. In addition, a two-electrode cell setup is constructed with an operating cell voltage of 1.512 V for delivering 10 mAcm⁻² current density. This study illustrates the new strategy of designing heterostructure catalysts for electrocatalytic UOR. Full article

(This article belongs to the Special Issue Homogeneous and Heterogeneous Catalytic Oxidation and Reduction)

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12 pages, 7657 KiB

Open AccessArticle

Cation Vacancies Anchored Transition Metal Dopants Based on a Few-Layer Ti₃C₂T_x Catalyst for Enhanced Hydrogen Evolution

by Xiangjie Liu, Xiaomin Chen, Chunlan Huang, Sihan Sun, Ding Yuan and Yuhai Dou

Catalysts 2025, 15(7), 663; https://doi.org/10.3390/catal15070663 - 7 Jul 2025

Viewed by 189

Abstract

This study addresses the efficiency and cost challenges of hydrogen evolution reaction (HER) catalysts in the context of carbon neutrality strategies by employing a synergistic approach that combines cation vacancy anchoring and transition metal doping on two-dimensional (2D) MXenes. Using an in situ [...] Read more.

This study addresses the efficiency and cost challenges of hydrogen evolution reaction (HER) catalysts in the context of carbon neutrality strategies by employing a synergistic approach that combines cation vacancy anchoring and transition metal doping on two-dimensional (2D) MXenes. Using an in situ LiF/HCl etching process, the aluminum layers in Ti₃AlC₂ were precisely removed, resulting in a few-layer Ti₃C₂T_x MXene with an increased interlayer spacing of 12.3 Å. Doping with the transition metals Fe, Co, Ni, and Cu demonstrated that Fe@Ti₃C₂ provided the optimal HER performance, characterized by an overpotential (η₁₀) of 81 mV at 10 mA cm⁻², a low Tafel slope of 33.03 mV dec⁻¹, and the lowest charge transfer resistance (R_ct = 5.6 Ω cm²). Mechanistic investigations revealed that Fe’s 3d⁶ electrons induce an upward shift in the d-band center of MXene, improving hydrogen adsorption free energy and reducing lattice distortion. This research lays a solid foundation for the design of non-precious metal catalysts using MXenes and highlights future avenues in bimetallic synergy and scalability. Full article

(This article belongs to the Special Issue Novel Electrocatalysts for Boosting Oxygen/Hydrogen Evolution Reactions)

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18 pages, 10208 KiB

Open AccessArticle

Development of Ni-P-N-C/Nickel Foam for Efficient Hydrogen Production via Urea Electro-Oxidation

by Abdullah M. Aldawsari, Maged N. Shaddad and Saba A. Aladeemy

Catalysts 2025, 15(7), 662; https://doi.org/10.3390/catal15070662 - 7 Jul 2025

Viewed by 207

Abstract

Electrocatalytic urea oxidation reaction (UOR) is a promising dual-purpose approach for hydrogen production and wastewater treatment, addressing critical energy and environmental challenges. However, conventional anode materials often suffer from limited active sites and high charge transfer resistance, restricting UOR efficiency. To overcome these [...] Read more.

Electrocatalytic urea oxidation reaction (UOR) is a promising dual-purpose approach for hydrogen production and wastewater treatment, addressing critical energy and environmental challenges. However, conventional anode materials often suffer from limited active sites and high charge transfer resistance, restricting UOR efficiency. To overcome these issues, a novel NiP@PNC/NF electrocatalyst was developed via a one-step thermal annealing process under nitrogen, integrating nickel phosphide (NiP) with phosphorus and nitrogen co-doped carbon nanotubes (PNCs) on a nickel foam (NF) substrate. This design enhances catalytic activity and charge transfer, achieving current densities of 50 mA cm⁻² at 1.34 V and 100 mA cm⁻² at 1.43 V versus the reversible hydrogen electrode (RHE). The electrode’s high electrochemical surface area (235 cm²) and double-layer capacitance (94.1 mF) reflect abundant active sites, far surpassing NiP/NF (48 cm², 15.8 mF) and PNC/NF (39.5 cm², 12.9 mF). It maintains exceptional stability, with only a 16.3% performance loss after 35 h, as confirmed by HR-TEM showing an intact nanostructure. Our single-step annealing technique provides simplicity, scalability, and efficient integration of NiP nanoparticles inside a PNC matrix on nickel foam. This method enables consistent distribution and robust substrate adhesion, which are difficult to attain with multi-step or more intricate techniques. Full article

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

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10 pages, 1115 KiB

Open AccessArticle

Ab Initio Study of Ti Segregation on the Pd–Ti Alloy Surface in the Presence of Adsorbed Atomic Oxygen

by Yufeng Wen, Yanlin Yu, Huaizhang Gu, Yaya Shi, Guoqi Zhao, Yuanxun Li and Qiuling Huang

Catalysts 2025, 15(7), 661; https://doi.org/10.3390/catal15070661 - 7 Jul 2025

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Abstract

Surface segregation in bimetallic systems plays a critical role in material functionality, as electrochemical activity and catalytic performance are governed by the surface composition. To explore the influence of atomic oxygen on the surface composition of Pd–Ti alloys, density functional theory (DFT) simulations [...] Read more.

Surface segregation in bimetallic systems plays a critical role in material functionality, as electrochemical activity and catalytic performance are governed by the surface composition. To explore the influence of atomic oxygen on the surface composition of Pd–Ti alloys, density functional theory (DFT) simulations were utilized to analyze Ti segregation within Pd matrices. The adsorption behavior of atomic oxygen on Pd–Ti low-index (111), (100), and (110) surfaces was systematically investigated through energetic and electronic analyses. Simulation results reveal that Ti atoms prefer to remain in the bulk of the alloy under vacuum conditions, whereas oxygen adsorption induces significant Ti segregation to the surface layer. This oxygen-driven segregation is mechanistically linked to oxygen-surface bonding strength, as evidenced by correlating adsorption energetics with electronic structure modifications. These results provide a theoretical basis for engineering Pd–Ti alloys as high-performance catalysts in the oxygen reduction reaction. Full article

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15 pages, 4061 KiB

Open AccessFeature PaperArticle

Influence of Metal Compounds on Structural and Electrochemical Characteristics of Chars from PVC Pyrolysis

by Jiayou Sun, Tianyang Ding, Xue Zhao, Guorong Xu, Chang Wen and Jie Yu

Catalysts 2025, 15(7), 660; https://doi.org/10.3390/catal15070660 - 6 Jul 2025

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Abstract

This study aims to investigate the influence of various metal compounds (ZnO, ZnCl₂, Zn(OH)₂, MgO, MgCl₂, and Mg(OH)₂) on the structural and electrochemical properties of chars derived from the pyrolysis of polyvinyl chloride (PVC). Raw [...] Read more.

This study aims to investigate the influence of various metal compounds (ZnO, ZnCl₂, Zn(OH)₂, MgO, MgCl₂, and Mg(OH)₂) on the structural and electrochemical properties of chars derived from the pyrolysis of polyvinyl chloride (PVC). Raw PVC samples mixed with different metal compounds were firstly pyrolyzed at 500 °C in a fixed-bed reactor. The produced chars were further pyrolyzed at 800 °C. The objective was to evaluate the impact of these metal compounds on the char structure through comparative analysis. The pyrolytic chars were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. Zinc-based additives notably increased carbon yield to 32–34 wt.%, attributed to ZnCl₂-induced cross-linking. Specifically, ZnO facilitated porous architectures and aromatic structures with six or more rings. Mg-based compounds induce the formation of a highly stacked carbon structure primarily composed of crosslinked cyclic alkenes, rather than large polyaromatic domains. Upon further thermal treatment, these aliphatic-rich stacked structures can be progressively transformed into aromatic frameworks through dehydrogenation reactions at elevated temperatures. A high-surface-area porous carbon material (PVC/ZnO-800, SSA = 609.382 m² g⁻¹) was synthesized, demonstrating a specific capacitance of 306 F g⁻¹ at 1 A g⁻¹ current density. Full article

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

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18 pages, 4443 KiB

Open AccessArticle

Comparative Study on Ni/MgO-Al₂O₃ Catalysts for Dry and Combined Steam–CO₂ Reforming of Methane

by Tingting Zheng, Yuqi Zhou, Hongjie Cui and Zhiming Zhou

Catalysts 2025, 15(7), 659; https://doi.org/10.3390/catal15070659 - 6 Jul 2025

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Abstract

The dry reforming of methane (DRM) and the combined steam–CO₂ reforming of methane (CSCRM) are promising routes for syngas production while simultaneously utilizing two major greenhouse gases—CO₂ and CH₄. In this study, a series of Ni/MgO-Al₂O₃ [...] Read more.

The dry reforming of methane (DRM) and the combined steam–CO₂ reforming of methane (CSCRM) are promising routes for syngas production while simultaneously utilizing two major greenhouse gases—CO₂ and CH₄. In this study, a series of Ni/MgO-Al₂O₃ catalysts with varying Mg/Al molar ratios (Ni/MgAl(x), x = 0.5–0.9), along with Ni/MgO and Ni/Al₂O₃, were synthesized, characterized, and evaluated in both the DRM and CSCRM. Ni/MgO and Ni/Al₂O₃ exhibited a lower activity due to fewer active sites and a poor CH₄/CO₂ activation balance. In contrast, Ni/MgAl(0.6), Ni/MgAl(0.7), and Ni/MgAl(0.8) showed an enhanced activity, attributed to more abundant active sites and a more balanced activation of CH₄ and CO₂. Ni/MgAl(0.7) delivered the best DRM performance, whereas Ni/MgAl(0.8) was optimal for the CSCRM, likely due to its greater number of strong basic sites promoting CO₂ and H₂O adsorption. At 750 °C and 0.1 MPa over 100 h, Ni/MgAl(0.7) maintained a stable DRM performance (77% CH₄ and 86% CO₂ conversion; H₂/CO = 0.9) at 120 L/(g_cat·h), while Ni/MgAl(0.8) achieved a stable CSCRM performance (80% CH₄ and 62% CO₂ conversion; H₂/CO = 2.1) at 132 L/(g_cat·h). This study provides valuable insights into designing efficient Ni/MgO-Al₂O₃ catalysts for targeted syngas production. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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15 pages, 3237 KiB

Open AccessFeature PaperArticle

A Simple Fabrication of Tourmaline-Supported Ni-NiAl₂O₄ Nanocomposites for Enhanced Methane Dry Reforming Activity

by Jin Wang, Xianku Wang, Pengfei Zhou, Liang Bian and Fei Wang

Catalysts 2025, 15(7), 658; https://doi.org/10.3390/catal15070658 - 6 Jul 2025

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Abstract

Ni-based catalysts have been widely used in catalytic reactions by researchers due to their advantages such as abundant resources, high catalytic activity and lower prices than precious metals. However, the problems of easy agglomeration and poor dispersion of Ni-based catalysts have hindered their [...] Read more.

Ni-based catalysts have been widely used in catalytic reactions by researchers due to their advantages such as abundant resources, high catalytic activity and lower prices than precious metals. However, the problems of easy agglomeration and poor dispersion of Ni-based catalysts have hindered their large-scale application. Therefore, it is necessary to select a suitable preparation method to reduce the agglomeration of the catalyst and improve its dispersion. In this paper, the Ni-NiAl₂O₄/tourmaline composite material was prepared by using the microwave hydrothermal reduction method. The most favorable conditions for preparing NiAl₂O₄/tourmaline are as follows: using TEOA as the additive, the microwave hydrothermal temperature is 220 °C, the calcination temperature is 800 °C, and the addition amount of tourmaline is 7.4 wt.%. NiAl₂O₄ has a good dispersion over the surface of tourmaline support and the optimal NiAl₂O₄/tourmaline catalyst exhibits a specific surface area of 106.5 m²/g. Metallic nickel was reduced at 650 °C to further obtain Ni-NiAl₂O₄/tourmaline composites. Finally, the Ni-NiAl₂O₄/tourmaline composites showed significantly improved catalytic dry reforming of methane (DRM) activity compared to Ni-NiAl₂O₄ sample under low-temperature conditions (500–600 °C), meaning that the tourmaline carrier could effectively optimize the low-temperature catalytic performance of Ni-NiAl₂O₄. Full article

(This article belongs to the Special Issue Catalytic Reforming and Hydrogen Production: From the Past to the Future, 2nd Edition)

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17 pages, 989 KiB

Open AccessFeature PaperArticle

Combination of aza-Friedel Crafts MCR with Other MCRs Under Heterogeneous Conditions

by Giovanna Bosica and Roderick Abdilla

Catalysts 2025, 15(7), 657; https://doi.org/10.3390/catal15070657 - 6 Jul 2025

Viewed by 366

Abstract

Multicomponent reactions (MCRs) enable the efficient assembly of complex small molecules via multiple bond-forming events in a single step. However, individual MCRs typically yield products with similar core structures, limiting access to larger, more intricate scaffolds. Strategic selection of reactants allows the combination [...] Read more.

Multicomponent reactions (MCRs) enable the efficient assembly of complex small molecules via multiple bond-forming events in a single step. However, individual MCRs typically yield products with similar core structures, limiting access to larger, more intricate scaffolds. Strategic selection of reactants allows the combination of distinct MCRs, thus facilitating the synthesis of advanced molecular architectures with potential biological significance. Using our previously reported method for performing the aza-Friedel Crafts multicomponent reaction under green heterogeneous conditions, we have incorporated some of the obtained products into diverse multicomponent reactions to generate, in an unprecedent approach, eight novel products, some of which were also characterized by two-dimensional NMR techniques. The biological properties of such products are under investigation. Full article

(This article belongs to the Special Issue Multicomponent Catalytic Reactions Under Green Conditions, 2nd Edition)

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28 pages, 3496 KiB

Open AccessFeature PaperArticle

Production of 5-Hydroxymethylfurfural (HMF) from Sucrose in Aqueous Phase Using S, N-Doped Hydrochars

by Katarzyna Morawa Eblagon, Rafael G. Morais, Anna Malaika, Manuel Alejandro Castro Bravo, Natalia Rey-Raap, M. Fernando R. Pereira and Mieczysław Kozłowski

Catalysts 2025, 15(7), 656; https://doi.org/10.3390/catal15070656 - 5 Jul 2025

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Abstract

5-Hydroxymethylfurfural (HMF) is a versatile platform molecule with the potential to replace many fossil fuel derivatives. It can be obtained through the dehydration of carbohydrates. In this study, we present a simple and cost-effective microwave-assisted method for producing HMF. This method involves the [...] Read more.

5-Hydroxymethylfurfural (HMF) is a versatile platform molecule with the potential to replace many fossil fuel derivatives. It can be obtained through the dehydration of carbohydrates. In this study, we present a simple and cost-effective microwave-assisted method for producing HMF. This method involves the use of readily available sucrose as a substrate and glucose-derived bifunctional hydrochars as carbocatalysts. These catalysts were produced via hydrothermal carbonisation using thiourea and urea as nitrogen and sulphur sources, respectively, to introduce Brønsted acidic and basic sites into the materials. Using a microwave reactor, we found that the S, N-doped hydrochars were active in sucrose dehydration in water. Catalytic results showed that HMF yield depended on the balance between acidic and basic sites as well as the types of S and N species present on the surfaces of these hydrochars. The best-performing catalyst achieved an encouraging HMF yield of 37%. The potential of N, S-co-doped biochar as a green solid catalyst for various biorefinery processes was demonstrated. A simple kinetic model was developed to elucidate the kinetics of the main reaction pathways of this cascade process, showing a very good fit with the experimental results. The calculated rate constants revealed that reactions with a 5% sucrose loading exhibited significantly higher fructose dehydration rates and produced fewer side products than reactions using a more diluted substrate. No isomerisation of glucose into fructose was observed in an air atmosphere. On the contrary, a limited rate of isomerisation of glucose into fructose was recorded in an oxygen atmosphere. Therefore, efforts should focus on achieving a high glucose-to-fructose isomerisation rate (an intermediate reaction step) to improve HMF selectivity by reducing humin formation. Full article

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

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19 pages, 3246 KiB

Open AccessFeature PaperArticle

Direct Conversion of 1,3-Butanediol to 1,3-Butadiene over ZSM-22 Catalysts: Influence of the Si/Al Ratio

by Loïc Eloi, Jeroen Poissonnier, Arne De Landsheere, Dhanjay Sharma, Jaouad Al Atrach, Valérie Ruaux, Valentin Valtchev, Maarten K. Sabbe, Joris W. Thybaut and An Verberckmoes

Catalysts 2025, 15(7), 655; https://doi.org/10.3390/catal15070655 - 5 Jul 2025

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Abstract

ZSM-22 zeolites with different Si/Al ratios (38, 50, 80) were prepared via a hydrothermal synthesis method, investigated for the catalytic dehydration of 1,3-butanediol (1,3-BDO) to butadiene (BD) at 300 °C. The catalytic performance of the synthesized materials was related to their properties and [...] Read more.

ZSM-22 zeolites with different Si/Al ratios (38, 50, 80) were prepared via a hydrothermal synthesis method, investigated for the catalytic dehydration of 1,3-butanediol (1,3-BDO) to butadiene (BD) at 300 °C. The catalytic performance of the synthesized materials was related to their properties and compared to a commercial ZSM-22 zeolite (Si/Al = 30). ZSM-22 (50) exhibited a quick decline in conversion, a lower BD selectivity, and higher propylene selectivity compared to the other materials, which could be attributed to the presence of strong Lewis acid sites and silanol nests. The Lewis sites favor the cracking of the intermediate 3-buten-1-ol (3B1OL) into propylene, while the silanol nests interact with the free hydroxyl group of 3B1OL, potentially inhibiting further dehydration towards BD. The highest initial BD yield of 74% was observed over ZSM-22 (80), while the highest initial BD productivity of 2.7 g_BD·g⁻¹_cata·h⁻¹ was achieved over ZSM-22 (38). After 22 h time on stream (TOS), c-ZSM-22 and ZSM-22 (38) outperformed previously reported catalysts from the literature, with productivities amounting to 1.3 g_BD·g⁻¹_cata·h⁻¹ and 1.2 g_BD·g⁻¹_cata·h⁻¹, respectively, at a site time of 6.6 mol_H+·s·mol⁻¹_1,3-BDO. Full article

(This article belongs to the Special Issue Zeolites as Catalysts: Applications in Chemical Engineering, Energy Sources and Environmental Protection, 2nd Edition)

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22 pages, 2989 KiB

Open AccessFeature PaperArticle

Preparation and Screening of Ni-Based Catalysts for the Olive Oil Mill Wastewater Steam Reforming Process

by Cláudio Rocha, Miguel A. Soria and Luís M. Madeira

Catalysts 2025, 15(7), 654; https://doi.org/10.3390/catal15070654 - 4 Jul 2025

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Abstract

Olive mill wastewater (OMW) is a highly polluting effluent rich in organic pollutant compounds derived from olive oil production. In this work, the steam reforming reaction of OMW (OMWSR) was performed in a traditional reactor at 400 °C and different pressures (1–4 bar) [...] Read more.

Olive mill wastewater (OMW) is a highly polluting effluent rich in organic pollutant compounds derived from olive oil production. In this work, the steam reforming reaction of OMW (OMWSR) was performed in a traditional reactor at 400 °C and different pressures (1–4 bar) to treat and valorize this effluent. A commercial catalyst (Rh/Al₂O₃) was used as a reference sample and several new catalysts were prepared (Ni-Ru/Ce-SiO₂) using different preparation methods to study their effect on the activity and stability. The best-performing catalysts were also subjected to long-term operation experimental tests (24 h). It was observed that the preparation method used for the catalysts synthesis influenced the catalytic performance of the samples. In addition, temperature-programmed oxidation (TPO) analysis of the used catalyst showed the presence of carbon deposits: the results showed that periodic oxidative regeneration improved the catalyst stability and sustained H₂ production. Finally, it was verified that the Ni-Ru/Ce³ catalyst stood out during the experimental tests, exhibiting high catalytic activity along the stability test at 400 °C and 1 bar: H₂ yield always over 7 mol_H2·mol_OMW⁻¹ and total organic carbon (TOC) conversion always higher than 94%. Despite these promising results, further research is needed to assess the economic feasibility of scaling up the process. Additionally, future work could explore the development of catalysts with enhanced resistance to deactivation by carbon deposition. Full article

(This article belongs to the Special Issue Green Chemistry and Catalysis)

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38 pages, 6778 KiB

Open AccessReview

Challenges and Opportunities for g-C₃N₄-Based Heterostructures in the Photodegradation of Environmental Pollutants

by Eduardo Estrada-Movilla, Jhonathan Castillo-Saenz, Benjamín Valdez-Salas, Álvaro Ortiz-Pérez, Ernesto Beltrán-Partida, Jorge Salvador-Carlos and Esneyder Puello-Polo

Catalysts 2025, 15(7), 653; https://doi.org/10.3390/catal15070653 - 4 Jul 2025

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Abstract

Graphitic carbon nitride (g-C₃N₄) is emerging as one of the most promising non-metallic semiconductors for the degradation of pollutants in water by photocatalytic processes. Its exceptional reduction–oxidation (redox) potentials and adequate band gap of approximately 2.7 eV give it [...] Read more.

Graphitic carbon nitride (g-C₃N₄) is emerging as one of the most promising non-metallic semiconductors for the degradation of pollutants in water by photocatalytic processes. Its exceptional reduction–oxidation (redox) potentials and adequate band gap of approximately 2.7 eV give it the ability to absorb in the visible light range. However, the characteristic sensitivity to light absorption is limited, leading to rapid recombination of electron–hole pairs. Therefore, different strategies have been explored to optimize this charge separation, among which the formation of heterostructures based on g-C₃N₄ is highlighted. This review addresses recent advances in photocatalysis mediated by g-C₃N₄ heterostructures, considering the synthesis methods enabling the optimization of the morphology and active interface of these materials. Next, the mechanisms of charge transfer are discussed in detail, with special emphasis on type II, type S, and type Z classifications and their influence on the efficiency of photodegradation. Subsequently, the progress in the application of these photocatalysts for the degradation of water pollutants, such as toxic organic dyes, pharmaceutical pollutants, pesticides, and per- and polyfluoroalkyl substances (PFAS), are analyzed, highlighting both experimental advances and remaining challenges. Finally, future perspectives oriented towards the optimization of heterostructures, the efficiency of synthesis methods, and the practical application of these in photocatalytic processes for environmental remediation. Full article

(This article belongs to the Special Issue Design and Synthesis of Nanostructured Catalysts, 3rd Edition)

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19 pages, 5983 KiB

Open AccessArticle

Fabrication of CoP@P, N-CNTs-Deposited Nickel Foam for Energy-Efficient Hydrogen Generation via Electrocatalytic Urea Oxidation

by Hany M. Youssef, Maged N. Shaddad, Saba A. Aladeemy and Abdullah M. Aldawsari

Catalysts 2025, 15(7), 652; https://doi.org/10.3390/catal15070652 - 4 Jul 2025

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Abstract

The simultaneous generation of hydrogen fuel and wastewater remediation via electrocatalytic urea oxidation has emerged as a promising approach for sustainable energy and environmental solutions. However, the practical application of this process is hindered by the limited active sites and high charge-transfer resistance [...] Read more.

The simultaneous generation of hydrogen fuel and wastewater remediation via electrocatalytic urea oxidation has emerged as a promising approach for sustainable energy and environmental solutions. However, the practical application of this process is hindered by the limited active sites and high charge-transfer resistance of conventional anode materials. In this work, we introduce a novel CoP@P, N-CNTs/NF electrocatalyst, fabricated through a facile one-step thermal annealing technique. Comprehensive characterizations confirm the successful integration of CoP nanoparticles and phosphorus/nitrogen co-doped carbon nanotubes (P, N-CNTs) onto nickel foam, yielding a unique hierarchical structure that offers abundant active sites and accelerated electron transport. As a result, the CoP@P, N-CNTs/NF electrode achieves outstanding urea oxidation reaction (UOR) performance, delivering current densities of 158.5 mA cm⁻² at 1.5 V and 232.95 mA cm⁻² at 1.6 V versus RHE, along with exceptional operational stability exceeding 50 h with negligible performance loss. This innovative, multi-element-doped electrode design marks a significant advancement in the field, enabling highly efficient UOR and energy-efficient hydrogen production. Our approach paves the way for scalable, cost-effective solutions that couple renewable energy generation with effective wastewater treatment. Full article

(This article belongs to the Special Issue Nanocatalysts for Degradation of Environmental Pollutants and Hydrogen Generation)

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35 pages, 3949 KiB

Open AccessFeature PaperReview

The Influence of Defect Engineering on the Electronic Structure of Active Centers on the Catalyst Surface

by Zhekun Zhang, Yankun Wang, Tianqi Guo and Pengfei Hu

Catalysts 2025, 15(7), 651; https://doi.org/10.3390/catal15070651 - 3 Jul 2025

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Abstract

Defect engineering has recently emerged as a cutting-edge discipline for precise modulation of electronic structures in nanomaterials, shifting the paradigm in nanoscience from passive ‘inherent defect tolerance’ to proactive ‘defect-controlled design’. The deliberate introduction of defect—including vacancies, dopants, and interfaces—breaks the rigid symmetry [...] Read more.

Defect engineering has recently emerged as a cutting-edge discipline for precise modulation of electronic structures in nanomaterials, shifting the paradigm in nanoscience from passive ‘inherent defect tolerance’ to proactive ‘defect-controlled design’. The deliberate introduction of defect—including vacancies, dopants, and interfaces—breaks the rigid symmetry of crystalline lattices, enabling new pathways for optimizing catalysis performance. This review systematically summarizes the mechanisms underlying defect-mediated electronic structure at active sites regulation, including (1) reconstruction of the electronic density of states, (2) tuning of coordination microenvironments, (3) charge transfer and localization effects, (4) spin-state and magnetic coupling modulation, and (5) dynamic defect and interface engineering. These mechanisms elucidate how defect-induced electronic restructuring governs catalytic activity and selectivity. We further assess advanced characterization techniques and computational methodologies for probing defects-induced electronic states, offering deeper mechanistic insights at atomic scales. Finally, we highlight recent breakthroughs in defect-engineered nanomaterials for catalytic applications, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and beyond, while discussing existing challenges in scalability, defect stability, and structure–property causality. This review aims to provide actionable principles for the rational design of defects to tailor electronic structures toward next-generation energy technologies. 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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19 pages, 5973 KiB

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Chitosan-Modified SBA-15 as a Support for Transition Metal Catalysts in Cyclohexane Oxidation and Photocatalytic Hydrogen Evolution

by Assemgul S. Auyezkhanova, Alima K. Zharmagambetova, Eldar T. Talgatov, Aigul I. Jumekeyeva, Sandugash N. Akhmetova, Zhannur K. Myltykbayeva, Imge Kalkan, Atıf Koca, Akzhol A. Naizabayev and Aigul T. Zamanbekova

Catalysts 2025, 15(7), 650; https://doi.org/10.3390/catal15070650 - 3 Jul 2025

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Abstract

This work aims to study the catalytic properties of Fe, Cr, and Cu catalysts deposited on chitosan–silica (SBA-15) composites in liquid phase oxidation of cyclohexane (CH) with H₂O₂ and photocatalytic hydrogen evolution reaction. The catalysts were obtained by consecutive adsorption [...] Read more.

This work aims to study the catalytic properties of Fe, Cr, and Cu catalysts deposited on chitosan–silica (SBA-15) composites in liquid phase oxidation of cyclohexane (CH) with H₂O₂ and photocatalytic hydrogen evolution reaction. The catalysts were obtained by consecutive adsorption of chitosan (CS) and metal ions (Fe³⁺, Cr³⁺, Cu²⁺) on SBA-15 at ambient conditions. Characterization of the catalysts by XRD, IR spectroscopy, XPS, TEM, SEM, etc., showed the CS and metal ion adsorption on the solid support. Modification with CS provided better immobilization of the metal ions on SBA-15. The synthesized catalysts demonstrated different performance in liquid phase oxidation of cyclohexane with H₂O₂ under mild conditions at 40 °C and atmospheric pressure. Cyclohexane conversion on Fe–CS/SBA-15 (18.5%) and Cr–CS/SBA-15 (21.6%) was higher than on Cu–CS/SBA-15 (9.3%). The influence of different conditions of the reaction such as time, temperature, catalyst dosage, substrate and oxidant ratio on cyclohexane conversion in the presence of the most efficient Cr–CS/SBA-15 catalyst was also studied. The optimal reaction conditions were found to be the following: duration of reaction—4 h, temperature of reaction—50 °C, m_cat—0.03 g, a substrate/H₂O₂ ratio of 1:3. In addition, Cr–CS/SBA-15 and Fe–CS/SBA-15 catalysts were studied in a photocatalytic H₂ evolution reaction. The Fe-containing catalyst demonstrated superior efficiency in photocatalytic H₂ evolution. The total volume of hydrogen produced within 3 h was 103 mL/g. Thus, this study demonstrates that chitosan possesses promising potential in the design of the supported catalysts for cyclohexane oxidation and photocatalytic hydrogen evolution reactions. Full article

(This article belongs to the Special Issue Homogeneous and Heterogeneous Catalytic Oxidation and Reduction)

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12 pages, 3285 KiB

Open AccessArticle

Ceria Promoted Ni/SiO₂ as an Efficient Catalyst for Carbon Dioxide Reforming of Methane

by Hua-Ping Ren, Lin-Feng Zhang, Yu-Xuan Hui, Xin-Ze Wu, Shao-Peng Tian, Si-Yi Ding, Qiang Ma and Yu-Zhen Zhao

Catalysts 2025, 15(7), 649; https://doi.org/10.3390/catal15070649 - 2 Jul 2025

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Abstract

The Ni/SiO₂ and the ceria-promoted Ni-CeO₂/SiO₂ were prepared by the impregnation method and co-impregnation method, respectively. The performance of the carbon dioxide reforming of methane (CDR) over Ni/SiO₂ and Ni-CeO₂/SiO₂ was investigated under the conditions [...] Read more.

The Ni/SiO₂ and the ceria-promoted Ni-CeO₂/SiO₂ were prepared by the impregnation method and co-impregnation method, respectively. The performance of the carbon dioxide reforming of methane (CDR) over Ni/SiO₂ and Ni-CeO₂/SiO₂ was investigated under the conditions of CH₄/CO₂ = 1.0, T = 800 °C, and GHSV = 60,000 mL·g⁻¹·h⁻¹. As a result, a high CDR performance, especially stability, was obtained over Ni-CeO₂/SiO₂, in which the conversion of CH₄ was very similar to that of the thermodynamic equilibrium (88%), and a negligible decrease in CH₄ conversion was observed after 50 h of the CDR reaction. Ni/SiO₂ and Ni-CeO₂/SiO₂ before and after the CDR reaction were subjected to structural characterization by XRD, TEM, TG–DSC, and physical adsorption. It was found that the addition of CeO₂ into Ni/SiO₂ significantly affected its surface area, the size and dispersion of Ni, the reduction behavior, and the coking properties. Moreover, the redox property of Ce³⁺-Ce⁴⁺, which accelerates the gasification of the coke, made Ni-CeO₂/SiO₂ successfully operate for 50 h without observable deactivation. Thus, the developed catalyst is very promising for the CDR. Full article

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

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28 pages, 3287 KiB

Open AccessReview

Recent Progress in Photocatalytic Hydrogen Production Using 2D MoS₂ Based Materials

by Khursheed Ahmad and Tae Hwan Oh

Catalysts 2025, 15(7), 648; https://doi.org/10.3390/catal15070648 - 2 Jul 2025

Viewed by 434

Abstract

Due to the increase in energy demand, photocatalytic hydrogen (H₂) production has received enormous interest from the scientific community due to its simplicity and cost-effectiveness. The photocatalyst (PC) plays a vital role in H₂ evolution, and it is well understood [...] Read more.

Due to the increase in energy demand, photocatalytic hydrogen (H₂) production has received enormous interest from the scientific community due to its simplicity and cost-effectiveness. The photocatalyst (PC) plays a vital role in H₂ evolution, and it is well understood that an efficient PC should have a larger surface area and better charge separation and transport properties. Previously, extensive efforts were made to prepare the efficient PC for photocatalytic H₂ production. In some cases, pristine catalyst could not catalyze the catalytic reactions due to a fast recombination rate or poor catalytic behavior. Thus, cocatalysts can be explored to boost the photocatalytic H₂ production. In this regard, a promising cocatalyst should have a large surface area, more active sites, decent conductivity, and improved catalytic properties. Molybdenum disulfide (MoS₂) is one of the two-dimensional (2D) layered materials that have excellent optical, electrical, and physicochemical properties. MoS₂ has been widely utilized as a cocatalyst for the photocatalytic H₂ evolution under visible light. Herein, we have reviewed the progress in the fabrication of MoS₂ and its composites with metal oxides, perovskite, graphene, carbon nanotubes, graphitic carbon nitrides, polymers, MXenes, metal-organic frameworks, layered double hydroxides, metal sulfides, etc. for photocatalytic H₂ evolution. The reports showed that MoS₂ is one of the desirable cocatalysts for photocatalytic H₂ production applications. The challenges and future perspectives are also mentioned. This study may be beneficial for the researchers working on the design and fabrication of MoS₂-based PCs for photocatalytic H₂ evolution applications. Full article

(This article belongs to the Special Issue Catalytic Reforming and Hydrogen Production: From the Past to the Future, 2nd Edition)

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