Catalysts

52 pages, 1814 KiB

Open AccessReview

An Overview of the Advantages of Combining Photo- and Electrooxidation Processes in Actual Wastewater Treatment

by Laura Valenzuela, Beatriz Villajos, Sara Mesa Medina and Marisol Faraldos

Catalysts 2025, 15(1), 14; https://doi.org/10.3390/catal15010014 - 27 Dec 2024

The elimination of pollutants in real water and wastewater is a challenge for the successful application of electrooxidation processes (EOPs). The presence of inorganic salts in the reaction medium is of great relevance during EOPs, with active participation in the electrochemical reactions. A [...] Read more.

The elimination of pollutants in real water and wastewater is a challenge for the successful application of electrooxidation processes (EOPs). The presence of inorganic salts in the reaction medium is of great relevance during EOPs, with active participation in the electrochemical reactions. A revision of the reported devices used in the decontamination and disinfection of real wastewater demonstrated the main drawbacks of efficiently removing pollutants. However, the combination of photocatalytic processes with electrochemical technologies has been explored to improve overall efficiency and reduce energy consumption. A wide variety of materials, mainly metals, polymers, carbon and graphite derivatives, oxides, and MOFs, as well as their combinations, have been applied to electrodes and photoactive coatings. The deposition of the active layer has been enriched with novel designs, including porous hierarchical growth and 3D printing. The use of powerful characterization techniques allows for the study of the composition, structure, surface, and photo- and electrochemical performance of the fabricated electrodes. The simultaneous optimization of the operating conditions, parameters, and reactors must be specifically defined according to each water matrix. This approach will increase the efficiency of the whole process and contribute to cost savings. Economic contributions have been revised to calculate the cost of wastewater treatment. Full article

(This article belongs to the Special Issue State-of-the-Art of Heterostructured Photocatalysts)

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Graphical abstract

13 pages, 2854 KiB

Open AccessFeature PaperArticle

Enhanced CO₂ Photoreduction Performance of WO_3−x

by Yelan Cheng, Zhaolin Li and Xiaofei Yang

Catalysts 2025, 15(1), 13; https://doi.org/10.3390/catal15010013 - 27 Dec 2024

Abstract

Converting CO₂ greenhouse gases into high-value-added fuels via semiconductor photocatalysts is an ideal solution to address current environmental and energy issues. Due to its unique physicochemical traits and flexible structure, WO₃ is widely employed in photocatalysis. Nevertheless, it commonly faces problems [...] Read more.

Converting CO₂ greenhouse gases into high-value-added fuels via semiconductor photocatalysts is an ideal solution to address current environmental and energy issues. Due to its unique physicochemical traits and flexible structure, WO₃ is widely employed in photocatalysis. Nevertheless, it commonly faces problems such as limited light absorption and low reaction selectivity. Here, we effectively tackle the existing issue by introducing an oxygen defect strategy to synthesize two-dimensional WO_3−x nanosheets with rich oxygen vacancies. Due to localized surface plasmon resonance (LSPR), these nanosheets may exhibit broad light absorption and efficient CO₂ adsorption and activation. In the photocatalytic reduction of carbon dioxide (CO₂) to carbon monoxide (CO), WO_3−x nanosheets exhibited 100% selectivity and 16.1 μmol g⁻¹ h⁻¹ yield, 6.2 times higher than WO₃. Oxygen vacancies improve WO₃’s band structure and increase its capacity to absorb visible light. Based on electrochemical tests and fluorescence spectroscopy analysis, the outstanding functionality of WO_3−x nanosheets is related to the improved separation and transport of photocurrents and the restricted radiative recombination of the resulting electron pairs and holes. Full article

(This article belongs to the Section Photocatalysis)

10 pages, 2442 KiB

Open AccessCommunication

Residual Trifluorosulfonic Acid in Amino-Functionalized Covalent Triazine Frameworks for Boosting Photocatalytic Hydrogen Evolution

by Chengxiao Zhao, Zhaolin Li and Weiping Xiao

Catalysts 2025, 15(1), 12; https://doi.org/10.3390/catal15010012 - 26 Dec 2024

Abstract

The utilization of covalent triazine frameworks (CTFs) as photocatalysts has witnessed rapid advancements in the field of photocatalysis. However, the presence of residual components in certain CTFs materials is widely ignored as regards their influence on photocatalytic performance. In this study, we find [...] Read more.

The utilization of covalent triazine frameworks (CTFs) as photocatalysts has witnessed rapid advancements in the field of photocatalysis. However, the presence of residual components in certain CTFs materials is widely ignored as regards their influence on photocatalytic performance. In this study, we find that trifluorosulfonic acid (TfOH) molecules stably exist in the amino-functionalized CTF-NH₂ framework, which enhance the affinity for water. The experimental results indicate that the residual TfOH elevates the VB position of CTF-NH₂, facilitating the oxidization of both water and sacrificial agents. Moreover, the present of TfOH accelerates the separation and transfer of photogenerated charge carriers to the Pt cocatalyst. Consequently, CTF-NH₂-F containing residual TfOH molecules demonstrates a significant enhancement in the photocatalytic hydrogen evolution, achieving about 250 µmol over a duration of 3 h of illumination, which represents a 2.5-fold increase compared to that observed for CTF-NH₂. This research underscores the substantial impact that residues exert on photocatalytic performance. Full article

(This article belongs to the Special Issue Recent Advances in Environment and Energy Catalysis)

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12 pages, 2732 KiB

Open AccessFeature PaperArticle

Tuning Surface State in CoFe (Oxy)Hydroxide for Improved Oxygen Evolution Electrocatalysis

by Wen Guo, Chizhong Wang, Lei Qiu, Fanghua Liu, Sizhe Chen and Huazhen Chang

Catalysts 2025, 15(1), 11; https://doi.org/10.3390/catal15010011 - 26 Dec 2024

Abstract

CoFe-based catalysts have shown excellent activity for the oxygen evolution reaction (OER), with the oxidation states of the active sites playing a crucial role in determining catalytic performance. However, how to effectively increase the oxidation state of these active sites remains a key [...] Read more.

CoFe-based catalysts have shown excellent activity for the oxygen evolution reaction (OER), with the oxidation states of the active sites playing a crucial role in determining catalytic performance. However, how to effectively increase the oxidation state of these active sites remains a key challenge. In this work, a facile treatment with NaBH₄ solution was employed to modulate the surface state of CoFeO_xH_y catalysts, inducing an enhanced OER activity. The overpotential at 10 mA cm⁻² for the NaBH₄-treated CoFe catalyst was reduced to 270 mV, indicating improved OER activity. X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) results reveal that NaBH₄ treatment induced a phase reconstruction of the CoFe oxalate framework, a critical step in enhancing its catalytic properties. The strong reducing ability of NaBH₄ strengthened the Co-Fe interaction, allowing the retention of low-valence Co species while facilitating the formation of high-valence Fe sites. This dual modulation of Co and Fe oxidation states significantly accelerated charge transfer kinetics, ultimately boosting OER performance. These findings highlight the importance of improving the oxidation states of active sites in CoFe-based catalysts, providing insights for developing efficient catalysts for electrochemical water splitting. Full article

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

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11 pages, 4165 KiB

Open AccessArticle

Preparation and Application of Highly Efficient Self-Cleaning Coating g-C₃N₄/MoS₂@PDMS

by Chunhua Gao, Yifei Sima, Cong Xiang and Zerun Lv

Catalysts 2025, 15(1), 10; https://doi.org/10.3390/catal15010010 - 26 Dec 2024

Abstract

Photocatalytic coatings are capable of achieving pollution-free degradation of organic pollutants on the surface of buildings. The preparation of photocatalytic coatings with high degradation efficiency, stability and durability constitutes a significant challenge in current widespread applications. This study prepared g-C₃N₄ [...] Read more.

Photocatalytic coatings are capable of achieving pollution-free degradation of organic pollutants on the surface of buildings. The preparation of photocatalytic coatings with high degradation efficiency, stability and durability constitutes a significant challenge in current widespread applications. This study prepared g-C₃N₄/MoS₂ photocatalytic materials through a simple hydrothermal combined low-temperature calcination process, and selected the materials through characterization and photocatalytic degradation of organic wastewater experiments. Finally, poly(dimethylsiloxane) (PDMS) was added to obtain a g-C₃N₄/MoS₂@PDMS coating. The coating was applied to the concrete surface, and, in the experiment, the coating showed good durability, stability, and high photocatalytic activity. Full article

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

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25 pages, 8269 KiB

Open AccessArticle

Hydrogen Production from Ethanol Steam Reforming by Stable LaNi_xCu_1−xO_3−λ Perovskite-Type Catalysts

by Chenjie Ruan, Binlin Dou, Na Chen and Hua Zhang

Catalysts 2025, 15(1), 9; https://doi.org/10.3390/catal15010009 - 26 Dec 2024

Abstract

Hydrogen production from ethanol steam reforming (ESR) was performed using the synthesized LaNi_xCu_1−xO_3−λ perovskite-type catalysts in a continuous two-stage fixed-bed reactor from 450 to 700 °C under atmospheric pressure. The elemental analysis (EA), XRD, SEM, BET, and TGA-DTG [...] Read more.

Hydrogen production from ethanol steam reforming (ESR) was performed using the synthesized LaNi_xCu_1−xO_3−λ perovskite-type catalysts in a continuous two-stage fixed-bed reactor from 450 to 700 °C under atmospheric pressure. The elemental analysis (EA), XRD, SEM, BET, and TGA-DTG technologies were used to characterize the structures and properties of the synthesized catalysts. The thermodynamic equilibrium model, based on the minimization of Gibbs free energy using a non-stoichiometric methodology, was carried out and compared with experimental data. The results demonstrated that the catalytic activity of the perovskite-type catalysts for ESR can be improved after modification with a certain amount of copper (about 0.67 mmol/g) and decreased further with an increase in copper content (about 3.41 mmol/g). The most active catalyst was found to be LaNi_0.9Cu_0.1O_3−λ, with an ethanol conversion value of 96.0% and hydrogen selectivity of 71.3%. The perovskite-type catalysts with an appropriate amount of Cu promoter improved coking resistance and presented excellent stability with no loss of activity over 101 h at 700 °C. Based on the power-law kinetic model with the first reaction order, the activation energy and the frequency factor for ethanol steam reforming by perovskite-type catalysts were calculated. Our studies indicated the enhanced effects of Ni and Cu on the small Ni-Cu bimetallic particles in the water gas shift (WGS) reaction, which could also contribute to the activity and stability of the LaNi_xCu_1−xO_3−λ perovskite-type catalysts in hydrogen production. Full article

(This article belongs to the Special Issue State-of-the-Art Catalytic Conversion of Biomass and Their Derivatives in Asia)

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20 pages, 13753 KiB

Open AccessFeature PaperArticle

Electrolessly Deposited Cobalt–Phosphorus Coatings for Efficient Hydrogen and Oxygen Evolution Reactions

by Huma Amber, Aldona Balčiūnaitė, Zita Sukackienė, Loreta Tamašauskaitė-Tamašiūnaitė and Eugenijus Norkus

Catalysts 2025, 15(1), 8; https://doi.org/10.3390/catal15010008 - 24 Dec 2024

Abstract

Hydrogen production via water splitting is one of the latest low-cost green hydrogen production technologies. The challenge is to develop inexpensive and highly active catalysts. Herein, we present the preparation of electrocatalysts based on cobalt–phosphorus (Co-P) coatings with different P contents for hydrogen [...] Read more.

Hydrogen production via water splitting is one of the latest low-cost green hydrogen production technologies. The challenge is to develop inexpensive and highly active catalysts. Herein, we present the preparation of electrocatalysts based on cobalt–phosphorus (Co-P) coatings with different P contents for hydrogen and oxygen evolution reactions (HER and OER). The Co-P coatings were deposited on the copper (Cu) surface using the economical and simple method of electroless metal deposition. The morphology, structure, and composition of the Co-P coatings deposited on the Cu surface were studied via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), while their activity for HER and OER in 1 M KOH was investigated using linear sweep voltammetry (LSV) and chrono-techniques. It was found that the catalyst activity for both HER and OER depends on the P content of the catalyst and varies based on the highest efficiency for each reaction. The Co-P coating with 11 wt% P exhibited the lowest overpotential value of 98.9 mV for the HER to obtain a current density of 10 mA cm⁻² compared to the Co-P coatings with 8, 5, 1.6, and 0.4 wt% P (107.6, 165.9, 218.2, and 253.9 mV, respectively). In contrast, the lowest OER overpotential (378 mV) was observed for the Co-P coating with 8 wt% P to obtain a current density of 10 mA cm⁻² as compared to the Co-P coatings with 5, 11, 1.6, and 0.4 wt% P (400, 413, 434, and 434 mV, respectively). These results suggest that the obtained catalysts are suitable for HER and OER in alkaline media. Full article

(This article belongs to the Special Issue Recent Advances in Energy-Related Materials in Catalysts, 2nd Edition)

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18 pages, 3112 KiB

Open AccessPerspective

Photocatalytic and Thermo-Photocatalytic Processes: Advantages of Modelling Light Irradiation and Temperature Profiles

by Mario J. Muñoz-Batista

Catalysts 2025, 15(1), 7; https://doi.org/10.3390/catal15010007 - 24 Dec 2024

Abstract

This contribution presents a personal perspective on the development of thermo-photocatalytic schemes. It discusses several concepts focused on the common presentation of catalytic and thermo-photocatalytic data, with special emphasis on the determination of TOF (Turnover Frequency) and Quantum Efficiency parameters. The importance of [...] Read more.

This contribution presents a personal perspective on the development of thermo-photocatalytic schemes. It discusses several concepts focused on the common presentation of catalytic and thermo-photocatalytic data, with special emphasis on the determination of TOF (Turnover Frequency) and Quantum Efficiency parameters. The importance of including temperature profiles and photon absorption rates in the analysis for intrinsic kinetic studies, comparison of catalytic results, and the potential scaling of reactors is highlighted. Additionally, topics related to the efficiency of the use of radiation and heat transfer are discussed. Photon absorption profiles are presented for a TiO₂ catalytic surface of 20 × 20 cm (both fluorescent and LED configuration), as well as the temperature profile obtained using a thermal resistance with a diameter of 5 cm in a flat reactor. Using this example, the importance of designing thermo-photocatalytic systems to ensure an acceptable level of homogeneity in light irradiation and temperature is discussed. The discussion provides data that positions thermo-photocatalytic processes in the early stages of research. It is still necessary to advance the understanding of phenomena occurring under mixed temperature and light conditions. Additionally, new materials that meet the required characteristics for each application need to be developed, along with the design of new thermo-photocatalytic reactors. Full article

(This article belongs to the Section Catalytic Materials)

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20 pages, 3762 KiB

Open AccessArticle

The Characteristics of Hydrodeoxygenation of Biomass Pyrolysis Oil over Alumina-Supported NiMo Catalysts

by Dong-Jin Seo, Jong Beom Lee, Yu-Jin Kim, Hye-Ryeong Cho, So-Yeon Kim, Ga-Eun Kim, Young-Duk Park, Geon-Hee Kim, Jung-Chul An, Kyeongseok Oh and Joo-Il Park

Catalysts 2025, 15(1), 6; https://doi.org/10.3390/catal15010006 - 24 Dec 2024

Abstract

The hydrodeoxygenation (HDO) of biomass pyrolysis oil (BPO) was evaluated in the presence of two commercial alumina-supported transition metal catalysts, NiMo/alumina-1 (NM1) and NiMo/alumina-2 (NM2). The study explored two characteristic aspects: how HDO reaction conditions affected the oxygen content, density, and boiling point [...] Read more.

The hydrodeoxygenation (HDO) of biomass pyrolysis oil (BPO) was evaluated in the presence of two commercial alumina-supported transition metal catalysts, NiMo/alumina-1 (NM1) and NiMo/alumina-2 (NM2). The study explored two characteristic aspects: how HDO reaction conditions affected the oxygen content, density, and boiling point distribution of BPO with varying temperature and HDO reaction time, and the roles of catalysts. Characterizations of HDO-treated oils included elemental analysis, GC-MS, SIMDIS, ¹³C NMR, and ¹H NMR, and characterizations of catalysts included NH₃-TPD, XRF, and TPO-MS analysis. The results show that both NM1 and NM2 catalysts removed oxygenated compounds effectively, which led to decreases in density and shifts toward higher boiling point distributions of BPO. Compared to the NM1 catalyst, NM2 had a higher acidity and enhanced HDO activity. The best HDO reaction performance was achieved in the presence of the NM2 catalyst at 300 °C. Furthermore, HDO reactions showed a significant amount of CO₂, CH₄, C₂H₆, and C₃H₈, which suggests that HDO reactions proceeded via a series of reactions of decarboxylation, water–gas shift, and methanation. In addition, hydrocarbon fraction tests suggested a favorable potential for the blending of HDO-treated biomass pyrolysis oil (HDO-BPO) with petroleum-derived fractions. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Sustainable Conversion of Biomass, Carbon Dioxide and Plastic Waste into Fuels and Chemicals)

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12 pages, 3872 KiB

Open AccessArticle

Towards Efficient Oxygen Reduction Reaction: One-Step Synthesis of Co-N Catalysts with Polyhexamethylene Guanidine as Nitrogen Precursor

by Ruyang Song, Lin Gu, Chuanyue Sun, Huaxing Li, Abdullah N. Alodhayb, Yunyun Dong and Jinsheng Zhao

Catalysts 2025, 15(1), 5; https://doi.org/10.3390/catal15010005 - 24 Dec 2024

Abstract

Developing non-noble metal catalysts that exhibit oxygen reduction reaction (ORR) activity comparable to or exceeding that of platinum-based catalysts remains a significant challenge. This research presents the successful fabrication of novel cobalt-nitrogen (Co-N) catalysts through a straightforward one-step synthesis method. This method involves [...] Read more.

Developing non-noble metal catalysts that exhibit oxygen reduction reaction (ORR) activity comparable to or exceeding that of platinum-based catalysts remains a significant challenge. This research presents the successful fabrication of novel cobalt-nitrogen (Co-N) catalysts through a straightforward one-step synthesis method. This method involves stirring a mixture of cobalt (II) nitrate, polyhexamethylene guanidine (PHMG) as a nitrogen source, and carbon spheres at ambient temperature. By varying the mass ratio of PHMG to cobalt salt, three distinct catalyst formulations were produced. The catalyst with an optimal PHMG-to-cobalt nitrate ratio of 2:1 (Co-PHMG-2@C) exhibited exceptional electrocatalytic activity for the oxygen reduction reaction (ORR) in alkaline electrolytes. This catalyst demonstrated a high onset potential of 0.97 V and a half-wave potential of 0.82 V versus the reversible hydrogen electrode (RHE), favorably comparable to those of the benchmark Pt/C catalyst (1.02 V vs. RHE). Furthermore, Co-PHMG-2@C displayed superior stability and resistance to methanol poisoning. The scalability of this synthesis technique offers a promising pathway for cost-effective and environmentally friendly production of carbon nanomaterials for applications in fuel cells and other electrochemical energy devices. Full article

(This article belongs to the Section Catalytic Materials)

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25 pages, 7157 KiB

Open AccessFeature PaperArticle

Green Synthesis of Photocatalytically Active ZnO Nanoparticles Using Chia Seed Extract and Mechanistic Elucidation of the Photodegradation of Diclofenac and p-Nitrophenol

by Yossra Ounis Dkhil, Tim Peppel, Michael Sebek, Jennifer Strunk and Ammar Houas

Catalysts 2025, 15(1), 4; https://doi.org/10.3390/catal15010004 - 24 Dec 2024

Abstract

Zinc oxide nanoparticles (ZnO NPs) were synthesized using a simple and eco-friendly precipitation method, employing a capping agent derived from chia seeds (Salvia hispanica). X-ray diffraction (XRD) analysis confirmed the formation of ZnO with a hexagonal crystal structure and an average [...] Read more.

Zinc oxide nanoparticles (ZnO NPs) were synthesized using a simple and eco-friendly precipitation method, employing a capping agent derived from chia seeds (Salvia hispanica). X-ray diffraction (XRD) analysis confirmed the formation of ZnO with a hexagonal crystal structure and an average crystallite size of less than 30 nm. Scanning electron microscopy (SEM) revealed distinct quasi-spherical and nanorod-like morphologies, while energy-dispersive X-ray spectroscopy (EDX) verified the presence of zinc and oxygen. Diffuse reflectance spectroscopy (DRS) indicated significant activity in the UV region, with the nanoparticles exhibiting a band gap of 3.25 eV. The photocatalytic efficiency of the synthesized ZnO NPs was evaluated through their ability to degrade diclofenac sodium (DCF) and para-nitrophenol (4-nitrophenol, PNP) under UV-LED irradiation, achieving pollutant removal rates exceeding 98%. The degradation mechanism is clarified by a detailed characterization of the reaction intermediates. These findings highlight the potential of ZnO NPs synthesized from chia seed extract for effective environmental remediation of pharmaceutical and organic pollutants. Full article

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

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24 pages, 9225 KiB

Open AccessArticle

Synthesis and Mechanism of Z-Scheme Heterojunction Photocatalyst MoS₂-WO₃

by Yuan Lu, Xinyu Wang, Yu Zhang, Siyuan Ren, Yukun Mei and Longjun Xu

Catalysts 2025, 15(1), 3; https://doi.org/10.3390/catal15010003 - 24 Dec 2024

Abstract

A novel spherical MoS₂/WO₃ composite was fabricated via a hydrothermal method for the photocatalytic degradation of RhB from wastewater. The structure and morphology of the photocatalyst were systematically characterized. The MoS₂/WO₃ nanospheres formed a p-n heterojunction, with [...] Read more.

A novel spherical MoS₂/WO₃ composite was fabricated via a hydrothermal method for the photocatalytic degradation of RhB from wastewater. The structure and morphology of the photocatalyst were systematically characterized. The MoS₂/WO₃ nanospheres formed a p-n heterojunction, with charge migration following a Z-scheme mechanism. The MoS₂/WO₃ composites exhibited superior photocatalytic activity, achieving a 94.5% degradation rate for RhB in just 60 min under visible light irradiation, far surpassing the performance of pure WO₃ and MoS₂. This enhanced activity was attributed to the improved charge separation efficiency and redox capacity, enabled by the unique “layer–bending layer” growth mode. The composite’s transfer resistance (R_ct) was as low as 7.42 × 10² Ω, promoting faster electrochemical reactions. With a maximum photocurrent density of 87 μA·cm⁻², the composite rapidly separated photogenerated electron–hole pairs. The primary reactive species in the photocatalytic reaction were ·OH and O₂⁻, with h⁺ playing a secondary role. Full article

(This article belongs to the Special Issue Advances in Enhancement of Catalytic Performance for Wastewater Treatment)

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14 pages, 5070 KiB

Open AccessArticle

Magnetically Assembled Electrode Incorporating Self-Powered Tourmaline Composite Particles: Exploiting Waste Energy in Electrochemical Wastewater Treatment

by Bo Zhang, Dan Shao, Yaru Wang, Hao Xu and Haojie Song

Catalysts 2025, 15(1), 2; https://doi.org/10.3390/catal15010002 - 24 Dec 2024

Abstract

A magnetically assembled electrode (MAE) is a modular electrode format in electrochemical oxidation wastewater treatment. MAE utilizes magnetic forces to attract the magnetic catalytic auxiliary electrodes (AEs) on the main electrode (ME), which has the advantages of high efficiency and flexible adjustability. However, [...] Read more.

A magnetically assembled electrode (MAE) is a modular electrode format in electrochemical oxidation wastewater treatment. MAE utilizes magnetic forces to attract the magnetic catalytic auxiliary electrodes (AEs) on the main electrode (ME), which has the advantages of high efficiency and flexible adjustability. However, the issue of the insufficient polarization of the AEs leaves the potential of this electrode underutilized. In this study, natural tourmaline (Tml) particles with pyroelectric and piezoelectric properties were utilized to solve the above issue by harvesting and converting the waste energy (i.e., the joule heating energy and the bubble striking mechanical energy) from the electrolysis environment into additional electrical energy applied on the AEs. Different contents of Tml particles were composited with Fe₃O₄/Sb-SnO₂ particles as novel AEs, and the structure–activity relationship of the novel MAE was investigated by various electrochemical measurements and orthogonal tests of dye wastewater treatment. The results showed that Tml could effectively enhance all electrochemical properties of the electrode. The optimal dye removal rate was obtained by loading the AEs with 0.2 g·cm⁻² when the Tml content was 4.5 wt%. The interaction of current density and Tml content had a significant effect on the COD removal rate, and the mineralization capacity of the electrode was significantly enhanced. The findings of this study have unveiled the potential application of minerals and energy conversion materials in the realm of electrochemical oxidation wastewater treatment. Full article

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

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13 pages, 4352 KiB

Open AccessArticle

Modulation of the Coordination Environment of Graphene-Loaded NiFe-LDH and PbO₂ Catalysts by Plasma for Oxygen Evolution Reaction

by Tingting Yang, Zheng Zhang, Fei Tan, Huayu Liu, Xingyu Li, Hongqi Wang and Qing Yang

Catalysts 2025, 15(1), 1; https://doi.org/10.3390/catal15010001 - 24 Dec 2024

Abstract

The generation of hydrogen through water electrolysis represents a significant advancement in the transition towards low-carbon energy systems. Graphene-supported catalysts have demonstrated significant potential in improving the oxygen evolution reaction (OER) among several electrocatalysts utilised for this process. Nonetheless, attaining exact control over [...] Read more.

The generation of hydrogen through water electrolysis represents a significant advancement in the transition towards low-carbon energy systems. Graphene-supported catalysts have demonstrated significant potential in improving the oxygen evolution reaction (OER) among several electrocatalysts utilised for this process. Nonetheless, attaining exact control over the morphology and electrical configuration of these catalysts continues to pose a considerable difficulty. This study presents the development of a highly effective electrocatalyst composed of graphene-supported NiFe LDH and PbO₂, incorporating sulphur anions into the structure by a plasma jet treatment method. By optimising the ratio of sulphur anions, we were able to fine-tune the local coordination environment, which effectively adjusted the properties of the OH and OOH intermediates, thereby improving the OER catalytic performance. The plasma treatment introduced vacancy defects into the catalyst, further regulating its surface morphology and electronic structure. After sulphur anion optimisation, the graphene-supported catalyst exhibited excellent electrocatalytic performance in alkaline environments, achieving an OER overpotential of 228 mV at 100 mA·cm⁻². This performance, along with exceptional stability, exceeds the majority of previously documented catalysts. The results underscore the promise of sulphur anion optimisation and plasma treatment in improving OER performance, providing significant insights for the advancement of highly effective water-splitting catalysts. Full article

(This article belongs to the Special Issue Non-Novel Metal Electrocatalytic Materials for Clean Energy)

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14 pages, 3394 KiB

Open AccessArticle

Enhanced Diclofenac Removal from Constructed Wetland Effluent Using a Photoelectrocatalytic System with N-TiO₂ Nanocrystal-Modified TiO₂ Nanotube Anode and Graphene Oxide/Activated Carbon Photocathode

by Xiongwei Liang, Shaopeng Yu, Bo Meng, Xiaodi Wang, Chunxue Yang, Chuanqi Shi and Junnan Ding

Catalysts 2024, 14(12), 954; https://doi.org/10.3390/catal14120954 - 23 Dec 2024

Abstract

This investigation reports on the efficacy of a photoelectrocatalysis (PEC) system enhanced by a nitrogen-doped TiO₂ nanocrystal-modified TiO₂ nanotube array (N-TiO₂ NCs/TNTAs) anode paired with a graphene oxide/activated carbon (GO/AC) photocathode for diclofenac removal from effluent. The FE-SEM and EDX [...] Read more.

This investigation reports on the efficacy of a photoelectrocatalysis (PEC) system enhanced by a nitrogen-doped TiO₂ nanocrystal-modified TiO₂ nanotube array (N-TiO₂ NCs/TNTAs) anode paired with a graphene oxide/activated carbon (GO/AC) photocathode for diclofenac removal from effluent. The FE-SEM and EDX analyses validated the elemental composition of the anode—27.56% C, 30.81% N, 6.03% O, and 26.49% Ti. The XRD results confirmed the anatase phase and nitrogen integration, essential for photocatalytic activity enhancement. Quantum chemical simulations provided a comprehensive understanding of the red-shifted absorption bands in N-TiO₂, and UV-vis DRS demonstrated a red-shift in absorption to the visible spectrum, indicating improved light utilization. The PEC configuration achieved a photocurrent density of 9.8 mA/dm², significantly higher than the unmodified and solely nitrogen-doped counterparts at 4.8 mA/dm² and 6.1 mA/dm², respectively. Notably, this system reduced diclofenac concentrations by 58% within 75 min, outperforming standard photocatalytic setups. These findings underscore the potential of N-TiO₂ NCs/TNTAs-AC-GO/PTFE composite material for advanced environmental photoelectrocatalytic applications. Full article

(This article belongs to the Special Issue Nanomaterials in Environmental Catalysis)

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16 pages, 4164 KiB

Open AccessArticle

Hydrogenolysis of Benzyl Phenyl Ether Using Nickel–Molybdenum Clay Catalysts—A Model for Cleaving Ether Linkages in Lignin

by Indri B. Adilina, Muhammad A. Fitriady, Ferensa Oemry, Fauzan Aulia, Nino Rinaldi, Gagus K. Sunnardianto, Ian P. Silverwood and Stewart F. Parker

Catalysts 2024, 14(12), 953; https://doi.org/10.3390/catal14120953 - 23 Dec 2024

Abstract

The solvent-free hydrogenolysis (HDL) of benzyl phenyl ether (BPE), a model for the C–O (α-O-4) linkage in lignin, was investigated using NiMo-pillared clay catalysts in their reduced (NiMoPR) and sulfided (NiMoPS) forms. NiMoPS show higher activity and selectivity to give an equimolar mixture [...] Read more.

The solvent-free hydrogenolysis (HDL) of benzyl phenyl ether (BPE), a model for the C–O (α-O-4) linkage in lignin, was investigated using NiMo-pillared clay catalysts in their reduced (NiMoPR) and sulfided (NiMoPS) forms. NiMoPS show higher activity and selectivity to give an equimolar mixture of toluene and phenol, demonstrating selective cleavage of the C_aliphatic–O of BPE, while non-equimolar amounts were found for NiMoPR. Strong acid sites are dominant in NiMoPS, giving a higher total acidity compared to NiMoPR, which explains the higher selectivity of the sulfided catalyst towards the HDL products and monomeric aromatics. To understand the interaction of BPE on the catalyst surface, we carried out a comprehensive investigation of the 2D potential energy surface (PES) of BPE and the vibrational spectra using neutron scattering and computational studies. The results suggest that BPE is weakly adsorbed on NiMoPS and the pillared clay support (PILC) via a van der Waals or H-bonding interaction, but they are strongly chemisorbed on the NiMoPR due to covalent bonding. Weakly adsorbed BPE allows higher mobility during diffusion to the catalytic site, which promotes the higher activity of NiMoPS for the HDL. This work demonstrates the potential use of clay-supported NiMo catalysts for lignin valorization and the future circular economy. Full article

(This article belongs to the Section Biomass Catalysis)

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16 pages, 2660 KiB

Open AccessReview

Enabling Catalysts for Carbonyl Sulfide Hydrolysis

by Xun Zhang, Xiaoyu Qiu and Rui Wang

Catalysts 2024, 14(12), 952; https://doi.org/10.3390/catal14120952 - 23 Dec 2024

Abstract

Carbonyl sulfide (COS), an organosulfur compound commonly present in industrial gases, poses significant challenges for environmental protection and industrial processes due to its toxicity. This paper reviews recent advancements in the development of catalysts for COS hydrolysis, emphasizing the effects of various supports [...] Read more.

Carbonyl sulfide (COS), an organosulfur compound commonly present in industrial gases, poses significant challenges for environmental protection and industrial processes due to its toxicity. This paper reviews recent advancements in the development of catalysts for COS hydrolysis, emphasizing the effects of various supports and active components on catalyst performance, as well as the mechanisms underlying the hydrolysis reaction. Traditional supports like γ-Al₂O₃ demonstrate high activity for COS hydrolysis but are susceptible to deactivation. In contrast, novel supports such as activated carbon, TiO₂, and ZrO₂ have garnered attention for their unique structures and properties. The incorporation of active components, including alkali metals, alkaline earth metals, transition metals, and rare earth metals, significantly enhances the hydrolysis efficiency and resistance to deactivation of the catalysts. Additionally, this paper outlines three primary mechanisms for COS hydrolysis: the alkali-catalyzed mechanism, the Langmuir–Hinshelwood model, and the Eley–Rideal model mechanism, as well as the thiocarbonate intermediate mechanism, which collectively elucidate the conversion of COS into the H₂S and CO₂ catalyzed by these systems. Future research efforts will concentrate on developing high-activity, high-stability, and cost-effective COS hydrolysis catalysts, along with a more in-depth exploration of the reaction mechanisms to facilitate the efficient removal of COS from industrial emissions. Full article

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17 pages, 5343 KiB

Open AccessArticle

In Situ Synthesis of Co₃O₄ Nanoparticles on N-Doped Biochar as High-Performance Oxygen Reduction Reaction Electrocatalysts

by Renata Matos, Jorge V. Manuel, António J. S. Fernandes, Victor K. Abdelkader-Fernández, Andreia F. Peixoto and Diana M. Fernandes

Catalysts 2024, 14(12), 951; https://doi.org/10.3390/catal14120951 - 23 Dec 2024

Abstract

The development of sustainable and high-performance oxygen reduction reaction (ORR) electrocatalysts is fundamental to fuel cell implementation. Non-precious transition metal oxides present interesting electrocatalytic behavior, and their incorporation into N-doped carbon supports leads to excellent ORR performance. Herein, we prepared a shrimp shell-derived [...] Read more.

The development of sustainable and high-performance oxygen reduction reaction (ORR) electrocatalysts is fundamental to fuel cell implementation. Non-precious transition metal oxides present interesting electrocatalytic behavior, and their incorporation into N-doped carbon supports leads to excellent ORR performance. Herein, we prepared a shrimp shell-derived biochar (CC), which was doped with nitrogen via a ball milling approach (N-CC), and then used as support for Co₃O₄ nanoparticles growth (N-CC@Co₃O₄). Co₃O₄ loading was optimized using three different amounts of cobalt precursor: 1.56, 2.33 and 3.11 mmol in N-CC@Co₃O₄_1, N-CC@Co₃O₄_2 and N-CC@Co₃O₄_3, respectively. Interestingly, all prepared electrocatalysts, including the initial biochar CC, presented electrocatalytic activity towards ORR. Both N-doping and the introduction of Co₃O₄ NPs had a significant positive effect on ORR performance. Meanwhile, the three composites showed distinct ORR behavior, demonstrating that it is possible to tune their electrocatalytic performance by changing the Co₃O₄ loading. Overall, N-CC@Co₃O₄_2 achieved the most promising ORR results, displaying an E_onset of 0.84 V vs. RHE, j_L of −3.45 mA cm⁻² and excellent selectivity for the 4-electron reduction (n = 3.50), besides good long-term stability. These results were explained by a combination of high content of pyridinic-N and graphitic-N, high ratio of pyridinic-N/graphitic-N, and optimized Co₃O₄ loading interacting synergistically with the porous N-CC support. Full article

(This article belongs to the Special Issue Advances in Biomass-Based Electrocatalysts)

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25 pages, 1711 KiB

Open AccessFeature PaperReview

Bimetallic and Trimetallic Catalysts Advancements in the Conventional and MW-Assisted Propane Dehydrogenation Process

by Olga Muccioli, Concetta Ruocco and Vincenzo Palma

Catalysts 2024, 14(12), 950; https://doi.org/10.3390/catal14120950 - 22 Dec 2024

Abstract

A huge variety of chemical commodities are built from propylene molecules, and its conventional production technologies (naphtha steam cracking and fluid catalytic cracking) are unable to satisfy C₃H₆’s increasing requirements. In this scenario, Direct Propane Dehydrogenation (PDH) provides a [...] Read more.

A huge variety of chemical commodities are built from propylene molecules, and its conventional production technologies (naphtha steam cracking and fluid catalytic cracking) are unable to satisfy C₃H₆’s increasing requirements. In this scenario, Direct Propane Dehydrogenation (PDH) provides a practical and reliable route for supplying this short demand due to the economic availability of the raw material (C₃H₈) and the high propylene selectivities. The main challenges of propane dehydrogenation technology are related to the design of very active catalysts with negligible byproduct formation. In particular, the issue of catalyst deactivation by coke deposition still requires further development. In addition, PDH is a considerable endothermic reaction, and the efficiency of this technology is strictly related to heat transfer management. Thus, this current review specifically discusses the recent advances in highly dispersed bimetallic and trimetallic catalysts proposed for the PDH reaction in both conventional-heated and microwave-heated reactors. From the point of view of catalyst development, the recent research is mainly addressed to obtain nanometric and single-atom catalysts and core–shell alloys: atomically dispersed metal atoms promote the desorption of surface-bonded propylene and inhibit its further dehydrogenation. The discussion is focused on the alternative formulations proposed in the last few years, employing active species and supports different from the classical Pt-Sn/Al₂O₃ catalyst. Concerning the conventional route of energy-supply to the catalytic bed, the advantage of using a membrane as well as fluidized bed reactors is highlighted. Recent developments in alternative microwave-assisted dehydrogenation (PDH) employing innovative catalytic systems based on silicon carbide (SiC) facilitate selective heating of the catalyst. This advancement leads to improved catalytic activity and propylene selectivity while effectively reducing coke formation. Additionally, it promotes environmental sustainability in the ongoing electrification of chemical processes. Full article

(This article belongs to the Special Issue Current Status and Future Aspects of Bimetallic and Trimetallic Catalysts)

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