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19 pages, 1890 KB

Open AccessArticle

Sustainable Biofuel Production from Sludge by Oleaginous Fungi: Effect of Process Variables on Lipid Accumulation

by Habib Ullah, Muzammil Anjum, Bushra Noor, Samia Qadeer, Rab Nawaz, Azeem Khalid, Aansa Rukaya Saleem, Bilal Kabeer, Abubakr M. Idris, Muhammad Tayyab Sohail and Zepeng Rao

Catalysts 2025, 15(11), 1009; https://doi.org/10.3390/catal15111009 - 27 Oct 2025

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Abstract

The current paper investigated the potential of oleaginous fungus Rhizopus oryzae B97 for lipid accumulation under varying process variables. The fungal strain was isolated from bread mold and analyzed for its potential to grow on sludge with simultaneous production of microbial lipids. The [...] Read more.

The current paper investigated the potential of oleaginous fungus Rhizopus oryzae B97 for lipid accumulation under varying process variables. The fungal strain was isolated from bread mold and analyzed for its potential to grow on sludge with simultaneous production of microbial lipids. The sludge sample was sourced from the wastewater treatment plant located in Sector I-9, Islamabad. The effects of various process variables, such as pH, temperature, carbon and nitrogen sources, and shaking, on lipid accumulation, cell dry weight (CDW), chemical oxygen demand (COD), and volatile solids (VS) removal were investigated. It was found that glucose and yeast promoted the maximum lipid accumulation. At the same time, the fungal biomass reached its maximum value of up to 64% at 30 °C and at pH 4 (CDW: 28 g/L). These process conditions also improved the sludge treatment efficiency, achieving 68% COD and 55% VS removal in 168 h. FTIR analysis of the accumulated lipids indicated strong characteristic peaks of functional groups associated with fatty acids. The GC-MS analysis confirmed the production of essential FAMEs required in biodiesel production from the corresponding fatty acids, such as oleic acid, palmitic acid, stearic acid, and erucic acid. Operation in a continuous-shaking aerobic batch reactor (CSABR) system under optimum conditions further improved the process efficiency. Overall, the results indicated the competent potential of oleaginous fungus Rhizopus oryzae B97 for lipid-based biofuel production through fatty acid transesterification. Full article

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

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14 pages, 1086 KB

Open AccessArticle

Magnetite-Catalyzed Enhancement of Heavy Oil Oxidation: Thermal and Kinetic Analysis of Fe(acac)₃ Effects on High-Temperature Oxidation Reactions

by Younes Djouadi, Mohamed-Said Chemam, Alexey A. Eskin, Alexey V. Vakhin and Mohammed Amine Khelkhal

Catalysts 2025, 15(10), 953; https://doi.org/10.3390/catal15100953 - 4 Oct 2025

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Abstract

This study investigates iron acetylacetonate (Fe(acac)₃) as a catalyst for enhancing high-temperature oxidation (HTO) during in situ combustion (ISC) of heavy oil. Thermal analysis revealed that Fe(acac)₃ decomposes at 360 °C to form crystalline magnetite (Fe₃O₄). [...] Read more.

This study investigates iron acetylacetonate (Fe(acac)₃) as a catalyst for enhancing high-temperature oxidation (HTO) during in situ combustion (ISC) of heavy oil. Thermal analysis revealed that Fe(acac)₃ decomposes at 360 °C to form crystalline magnetite (Fe₃O₄). This transformation precedes the HTO regime. Differential scanning calorimetry demonstrated significantly intensified HTO reactions in catalytic systems, as peak temperatures were lower than those in non-catalytic reactions. Kinetic analysis showed that the catalyst reduces HTO activation energy by 15.6%, substantially increasing reaction rates across the HTO temperature range. X-ray powder diffraction confirmed that the mixed-valence Fe²⁺/Fe³⁺ configuration in the magnetite structure facilitates electron transfer during oxidation, enabling more complete combustion at lower temperatures. These findings represent a novel approach to catalyst design, from general activity to temperature-specific activation for a more stable and efficient in situ combustion process. Full article

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

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17 pages, 2550 KB

Open AccessArticle

Degradation of Tetracycline by Laccase–Mediator System Using Tea Polyphenols as Mediator

by Ling Xu, Shuang Zhang, Hui Xu, Anzhou Ma, Guoqiang Zhuang, Shuhao Huo, Bin Zou, Jingya Qian, Guoqiang Guan and Feng Wang

Catalysts 2025, 15(10), 952; https://doi.org/10.3390/catal15100952 - 4 Oct 2025

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Abstract

Tetracycline antibiotics are widely used, but their resistance to degradation and persistence in the environment pose a potential risk of inducing antibiotic resistance, creating significant threats to both the environment and human health. This study established a laccase–mediator system (LMS) using natural green [...] Read more.

Tetracycline antibiotics are widely used, but their resistance to degradation and persistence in the environment pose a potential risk of inducing antibiotic resistance, creating significant threats to both the environment and human health. This study established a laccase–mediator system (LMS) using natural green tea polyphenols (GTPs) as mediators for efficient tetracycline degradation. Through analyzing the main GTP components and optimizing the reaction conditions, the degradation efficiency of the system was evaluated. The experimental results indicated that, among the various tea polyphenol components, epicatechin gallate (ECG) contributed the most significantly to the degradation efficiency. Under optimized conditions, the Lac-ECG system degraded over 98% of tetracycline within 3–4 min. Further optimization of the Lac-GTP system allowed us to identify the following optimal conditions: a GTP concentration of 1.0 mmol/L, laccase concentration of 1.0 mg/mL, pH of 6.0, and temperature of 25 °C. Under these conditions, a degradation rate of 95.07% was attained within 5 min, outperforming a system using the synthetic mediator ABTS. Additionally, metal ions such as Ca²⁺, Mg²⁺, Cu²⁺, Fe³⁺, Fe²⁺, and Ni²⁺ were found to enhance the degradation process, while Mn²⁺ and Hg²⁺ exhibited inhibitory effects. Antibacterial activity tests revealed that the degradation products completely lost their antimicrobial activity, demonstrating effective detoxification of tetracycline. In conclusion, the tea polyphenol-based laccase–mediator system developed in this study exhibits high efficiency, cost-effectiveness, and environmental friendliness, offering a promising strategy for the remediation of tetracycline-contaminated environments. Full article

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

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17 pages, 2176 KB

Open AccessFeature PaperArticle

A Study on Maximizing the Performance of a Concrete-Based TiO₂ Photocatalyst Using Hydrophilic Polymer Dispersion

by Jung Soo Kim, Kanghyeon Song, Jiwon Kim, Hyun-Ju Kang, Dayoung Yu, Hong Gun Kim and Young Soon Kim

Catalysts 2025, 15(10), 935; https://doi.org/10.3390/catal15100935 - 1 Oct 2025

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Abstract

This study investigated the correlation between the dispersion stability and photocatalytic efficiency of titanium dioxide (TiO₂) nanoparticles for the development of self-cleaning functional concrete. After pretreatment of P25 TiO₂ with aqueous solutions of polyvinyl alcohol (PVA), polyethylene glycol (PEG), and [...] Read more.

This study investigated the correlation between the dispersion stability and photocatalytic efficiency of titanium dioxide (TiO₂) nanoparticles for the development of self-cleaning functional concrete. After pretreatment of P25 TiO₂ with aqueous solutions of polyvinyl alcohol (PVA), polyethylene glycol (PEG), and polyethylene glycol methyl ether (PEGME), dynamic light scattering (DLS) and zeta potential measurements were performed, and as a result, a 0.1 wt% PVA solution was optimal for inhibiting aggregation, with an average hydrodynamic diameter of 1.4 µm and a zeta potential of −11 mV. In methylene blue photolysis, the reaction rate constant (k_app) was 1.71 × 10⁻² min⁻¹ (R² = 0.98), which was improved by 11.4 times compared to the control group, and was about twice as high in the concrete specimen experiment. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analyses confirmed an anatase-to-rutile ratio of 81:19 particle sizes of 10–30 nm, and a specific surface area of 58.985 m²·g⁻¹. As a result, it is suggested that PVA pretreatment is a practical method to effectively improve the photocatalytic performance of TiO₂-based self-cleaning concrete. Full article

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

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12 pages, 4562 KB

Open AccessArticle

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

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

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

Viewed by 451

Abstract

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

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

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

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20 pages, 3897 KB

Open AccessArticle

From Pigment to Photocatalyst: CdSe/CdS Solutions Mimicking Cadmium Red for Visible-Light Dye Degradation

by Julia Łacic and Anna Magdalena Kusior

Catalysts 2025, 15(9), 883; https://doi.org/10.3390/catal15090883 - 15 Sep 2025

Viewed by 607

Abstract

This study explores the dual functionality of cadmium-based pigments (CdS, CdSe, and CdS_1−xSe_x solid solutions) as historical colorants and visible-light photocatalysts. Synthesized pigments here replicated hues of traditional cadmium reds. At the same time, their photocatalytic efficiency was evaluated [...] Read more.

This study explores the dual functionality of cadmium-based pigments (CdS, CdSe, and CdS_1−xSe_x solid solutions) as historical colorants and visible-light photocatalysts. Synthesized pigments here replicated hues of traditional cadmium reds. At the same time, their photocatalytic efficiency was evaluated using model dyes, such as indigo carmine (anionic) and fuchsine (cationic), as a representative of heritage materials. Structural and optical characterization confirmed tunable bandgaps (1.63–2.28 eV) and phase-dependent microstructures, with CdS_1−xSe_x composites exhibiting compositional heterogeneity. Photocatalytic tests revealed specific degradation mechanisms. Indigo carmine degradation was dominated by superoxide radicals (O₂^•−), while fuchsine degradation relied on photogenerated electrons (e′). Scavenger experiments highlighted the synergistic role of reactive oxygen species (ROS) and charge carriers, with CdS and CdSe showing the highest activity. Intermediate composites displayed selective reactivity, suggesting trade-offs between phase homogeneity and surface interactions. Reduced photocatalytic efficiency in composites aligns with cultural heritage needs, where pigment stability under light exposure is critical. This work bridges material science and conservation, demonstrating how the compositional tuning of CdS_1−xSe_x can balance color fidelity, photocatalytic activity, and longevity in art preservation. Full article

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

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14 pages, 3413 KB

Open AccessArticle

Study on the Catalytic Effect of Nano Copper Oxide with Different Particle Sizes on the Thermal Decomposition of Ammonium Perchlorate

by Hongfeng Ji, Xiaolin Tang, Lin Fu, Junyu Li, Zeyu Zheng, Chongtao Ding, Yifu Zhang and Chi Huang

Catalysts 2025, 15(9), 882; https://doi.org/10.3390/catal15090882 - 15 Sep 2025

Viewed by 603

Abstract

Ammonium perchlorate (AP), as the most commonly used oxidizer in composite solid propellants, achieving its rapid decomposition at lower temperatures, is one of the key items used to improve propellant performance. Copper-based catalysts, due to their good performance in promoting AP decomposition and [...] Read more.

Ammonium perchlorate (AP), as the most commonly used oxidizer in composite solid propellants, achieving its rapid decomposition at lower temperatures, is one of the key items used to improve propellant performance. Copper-based catalysts, due to their good performance in promoting AP decomposition and improving propellant combustion characteristics, are currently one of the most widely used catalyst types. However, the catalytic performance of copper-based catalysts for the decomposition of ammonium perchlorate, including the decomposition products, changes in the kinetic process during the decomposition, and the combustion process needs further research and clarification in terms of the influencing factors and mechanisms. Based on this question, to further analyze the essence of copper-based catalysts and the decomposition mechanism of CuO-catalyzed ammonium perchlorate, as well as its relationship with particle size, this paper compared and studied the effects of two different particle size CuO catalysts (small-diameter CuO-S and large-diameter CuO-L) on the thermal decomposition and combustion performance of AP. The results indicate that the decomposition of AP catalyzed by CuO mainly includes two stages: the initial low-temperature decomposition stage accelerated by the electron transfer mechanism and the subsequent second stage accelerated by the adsorption and conversion of intermediates by the catalyst. The two stages are controlled by different properties and are related to the particle size of the catalyst. This work provides in-depth research on CuO catalysts for the thermal decomposition of AP. Full article

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

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16 pages, 5209 KB

Open AccessArticle

Elucidating the Synergism by Applying Ni-Cu/Cr₂O₃ Catalysts for Green Methanol Fuel Synthesis by CO₂ Hydrogenation

by Israf Ud Din, Abdulrahman I. Alharthi, Mshari A. Alotaibi, Md Afroz Bakht, Rida Ihsan, Tooba Saeed, Ho Soon Min and Abdul Naeem

Catalysts 2025, 15(9), 877; https://doi.org/10.3390/catal15090877 - 12 Sep 2025

Viewed by 630

Abstract

The CO₂ hydrogenation process is thought to be one of the feasible methods for producing methanol fuel, which might be used to fulfill future energy demands. Improving the catalytic efficiency and understanding of the process are essential elements for the viability of [...] Read more.

The CO₂ hydrogenation process is thought to be one of the feasible methods for producing methanol fuel, which might be used to fulfill future energy demands. Improving the catalytic efficiency and understanding of the process are essential elements for the viability of CO₂ conversion routes. Here, a co-precipitation method was used to synthesize Ni-Cu bimetallic catalysts supported by chromium oxide (Cr₂O₃). To examine nickel (Ni)’s promoting role, the synthesized catalysts were incorporated with different concentrations of Ni. The N₂ adsorption–desorption isotherm exposed the mesoporous nature of Cr₂O₃-based Ni-Cu catalysts. A Fourier Transform Infrared (FTIR) spectroscopy investigation revealed the effective doping of Ni-Cu metal oxides on the surface of Cr₂O₃ by instigating an FTIR absorption band in the region associated with the FTIR absorption of metal oxides. The uniform morphology and homogenous, as well as highly dispersed, form of both Ni and Cu metal were recorded using a Field Emission Scanning Electron Microscope (FESEM) and X-ray Diffraction (XRD) techniques. The surface chemistry, metal–metal, and metal–support interactions of the Ni-Cu/Cr₂O₃ catalysts were disclosed via temperature program reduction (TPR) as well as X-ray photoelectron spectroscopy (XPS). The synergism between the Ni and Cu metals was revealed using both XPS and TPR techniques, which resulted in improving the catalytic profile of Ni-Cu/Cr₂O₃ catalysts. The activity data obtained by applying a slurry reactor demonstrated the active profile of Ni for CO₂ reduction to methanol in terms of the methanol synthesis rate. The promoting role of Ni was established by observing the progressing and linear increase in methanol selectivity by Ni enrichment to the Ni-Cu/Cr₂O₃ catalysts. Structure and activity studies recognized the promoting role of Ni by experiencing metal–metal and metal–support interactions with highly dispersed metal oxides over the Cr₂O₃ support in the current case. Full article

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

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17 pages, 3449 KB

Open AccessFeature PaperArticle

Structure of Cu, Ni, and CuNi Bimetallic Small Clusters Incorporated in g-C₃N₄: A DFT Study

by Agnieszka Drzewiecka-Matuszek, Priti Sharma and Dorota Rutkowska-Zbik

Catalysts 2025, 15(9), 861; https://doi.org/10.3390/catal15090861 - 6 Sep 2025

Viewed by 765

Abstract

Graphitic carbon nitride is recognized as a very promising support structure to anchor single atoms and small, sub-nanometric metal clusters, with vast applications in catalysis. In the current manuscript, we aim to study the geometry and electronic structures of the small, sub-nanometric monometallic [...] Read more.

Graphitic carbon nitride is recognized as a very promising support structure to anchor single atoms and small, sub-nanometric metal clusters, with vast applications in catalysis. In the current manuscript, we aim to study the geometry and electronic structures of the small, sub-nanometric monometallic (copper or nickel) and bimetallic (copper–nickel) clusters anchored to the graphitic carbon nitride. Our Density Functional Theory (DFT) study reveals that Cu and Ni, when in the form of isolated single atoms, lie in the plane of the support. Once the atoms agglomerate and form small clusters, they tend to bind above the carbon nitride (C₃N₄) plane. The nickel atoms form shorter bonds with the support than the copper atoms do, which is reflected by the binding energies. Atoms directly bound to the support become oxidized, forming electrophilic sites at the surface. The computed negative metal–support binding energies mean that the investigated Cu/Ni-C₃N₄ composites are stable, and the metal species will not easily leach from the support. Full article

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

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15 pages, 1803 KB

Open AccessFeature PaperArticle

Efficient and Stable Synthesis of Solketal on Mesoporous Aluminum Phosphate Catalyst

by Jingchen Wu, Jingwen Zhao, Yixiao Zhang, Xiujing Zou, Xingfu Shang and Xueguang Wang

Catalysts 2025, 15(9), 843; https://doi.org/10.3390/catal15090843 - 2 Sep 2025

Viewed by 811

Abstract

Solketal is an important chemical product with widespread applications, and the raw materials glycerol and acetone are inexpensive, making it highly economically viable. The glycerol-acetone condensation reaction is a typical acid-catalyzed reaction. Traditional homogeneous acidic catalysts cause significant environmental pollution and are difficult [...] Read more.

Solketal is an important chemical product with widespread applications, and the raw materials glycerol and acetone are inexpensive, making it highly economically viable. The glycerol-acetone condensation reaction is a typical acid-catalyzed reaction. Traditional homogeneous acidic catalysts cause significant environmental pollution and are difficult to recover. Herein, PEG-800 was used as an additive, and a one-pot process was employed to prepare a series of aluminum phosphate catalysts (xP-Al-O) with different P/Al molar ratios. The physical and chemical properties of the prepared xP-Al-O catalysts were thoroughly investigated using XRD, FTIR, SEM, Py-FTIR, BET, and NH₃ (CO₂)-TPD methods. The results indicated that different P/Al molar ratios indeed affect the catalyst structure, and all prepared xP-Al-O samples exist in the form of amorphous aluminum phosphate, with weak acidic sites dominating the surface. The prepared catalysts were investigated for their catalytic behavior in the acetalization reaction of glycerol and acetone. The 1.1P-Al-O catalyst exhibited the highest acetone glycerol acetal yield and demonstrated good catalytic stability. Full article

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

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14 pages, 3639 KB

Open AccessFeature PaperArticle

Computational Evaluation of Defects in Fe–N₄-Doped Graphene for Electrochemical CO₂ Reduction

by Kewei Yu, Xinyu Liu, Meiyan Wang and Jingyao Liu

Catalysts 2025, 15(9), 837; https://doi.org/10.3390/catal15090837 - 1 Sep 2025

Viewed by 781

Abstract

Single-atom catalysts supported by two-dimensional materials have been widely used in the electrochemical CO₂ reduction reaction (CO₂RR). Defects are inevitably generated during the preparation of two-dimensional materials. In this study, six Fe–N₄-doped graphene catalysts (CAT1–CAT6) containing single carbon [...] Read more.

Single-atom catalysts supported by two-dimensional materials have been widely used in the electrochemical CO₂ reduction reaction (CO₂RR). Defects are inevitably generated during the preparation of two-dimensional materials. In this study, six Fe–N₄-doped graphene catalysts (CAT1–CAT6) containing single carbon vacancy defects were designed and calculated using density functional theory (DFT) calculations. The stability, catalytic activity and product selectivity of these catalysts for CO₂RR to C₁ products CO, HCOOH, CH₃OH and CH₄ were discussed and compared with the defect-free Fe−N₄-doped graphene catalyst (CAT0). The results show that CAT1–CAT6 all exhibit excellent thermodynamic and electrochemical stabilities. The possible reaction pathways for CO₂ reduction to different C₁ products were systematically investigated. The CAT2, CAT3 and CAT6 exhibit high selectivity for HCOOH, whereas the products of CAT1, CAT4 and CAT5 are HCOOH, CH₃OH and CH₄, the same as those of CAT0. Moreover, these six catalysts more effectively suppress the competing hydrogen evolution reaction (HER) compared to CAT0, indicating that the defect improves the catalytic selectivity of CO₂RR. Among all of the catalysts, CAT2 demonstrates the most prominent catalytic activity and selectivity toward the CO₂ reduction reaction (CO₂RR). The large distortion of Fe−N₄ in *HCOO with CAT2 contributes to the lower limiting potential U_L. We hope that the finding that the large distortion of Fe−N₄ could lower the limiting potential will provide theoretical insights for the design of more efficient CO₂RR electrocatalysts. Full article

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

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13 pages, 3882 KB

Open AccessFeature PaperArticle

Energy-Saving-Targeted Solar Photothermal Dehydration and Confined Catalytic Pyrolysis of Oily Sludge Using Wood Sponge Loaded with Carbon Dots

by Chujun Luan, Huiyi Mao, Fawei Lin and Hongyun Yao

Catalysts 2025, 15(8), 764; https://doi.org/10.3390/catal15080764 - 9 Aug 2025

Viewed by 644

Abstract

Pyrolysis of oily sludge (OS) faces two significant challenges, dehydration in emulsion and coke formation, which cause extra energy consumption. Targeting energy saving, this paper first reported on solar photothermal dehydration and confined catalytic pyrolysis of OS using a single material. A wood [...] Read more.

Pyrolysis of oily sludge (OS) faces two significant challenges, dehydration in emulsion and coke formation, which cause extra energy consumption. Targeting energy saving, this paper first reported on solar photothermal dehydration and confined catalytic pyrolysis of OS using a single material. A wood sponge loaded with carbon dots (CM-CDs) can generate heat by absorbing solar energy and promote rapid phase separation and water transport via capillary action of oil–water emulsion in OS under sunlight. Almost all free water in OS with varied content can be removed after 3 h. Hydrocarbons entered the internal space of CM-CDs instead of contacting with soil minerals, contributed to the subsequent confined catalytic pyrolysis, led to a reduction in Ea (35.61 kJ/mol), inhibited coking and caking, and yielded higher oil recovery efficiency. In addition, CDs can form hotspots to enhance pyrolytic behaviors in local regions. When the ratio of OS to CM-CDs reached 10:0.6, the recovery rate of the oil fraction through combined pyrolysis was as high as 89%, which was 17% higher than that of OS pyrolysis alone. This discovery provides a new way to solve the bottleneck problems of OS pyrolysis in the industry. Full article

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

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20 pages, 2213 KB

Open AccessArticle

ANCUT1, a Fungal Cutinase MgCl₂-Activated by a Non-Essential Activation Mechanism for Poly(ethylene terephthalate) Hydrolysis

by José Augusto Castro-Rodríguez, Karla Fernanda Ramírez-González, Francisco Franco-Guerrero, Andrea Sabido-Ramos, Ilce Fernanda Abundio-Sánchez, Rogelio Rodríguez-Sotres, Adela Rodríguez-Romero and Amelia Farrés

Catalysts 2025, 15(8), 757; https://doi.org/10.3390/catal15080757 - 7 Aug 2025

Cited by 1 | Viewed by 1056

Abstract

Plastic waste, particularly poly(ethylene terephthalate) (PET), negatively impacts the environment and human health. Biotechnology could become an alternative to managing PET waste if enzymes ensure the recovery of terephthalic acid with efficiencies comparable to those of chemical treatments. Recent research has highlighted the [...] Read more.

Plastic waste, particularly poly(ethylene terephthalate) (PET), negatively impacts the environment and human health. Biotechnology could become an alternative to managing PET waste if enzymes ensure the recovery of terephthalic acid with efficiencies comparable to those of chemical treatments. Recent research has highlighted the potential of fungal cutinases, such as wild-type ANCUT1 (ANCUT1^wt) from Aspergillus nidulans, in achieving PET depolymerization. Fungal cutinases’ structures differ from those of bacterial cutinases, while their PET depolymerization mechanism has not been well studied. Here, a reliable model of the ANCUT1^wt was obtained using AlphaFold 2.0. Computational chemistry revealed potential cation-binding sites, which had not been described regarding enzymatic activation in fungal cutinases. Moreover, it allowed the prediction of residues with the ability to interact with a PET trimer that were mutation candidates to engineer the substrate binding cleft, seeking enhancements of PET hydrolysis. Enzyme kinetics revealed that both ANCUT1^wt and ANCUT1^N73V/L171Q (DM) were activated by MgCl₂, increasing the dissociation constant of the substrate and maximal reaction rate. We found that in the presence of MgCl₂, DM hydrolyzed different PET samples and released 9.1-fold more products than ANCUT1^wt. Scanning Electron Microscopy revealed a different hydrolysis mode of these enzymes, influenced by the polymer’s crystallinity and structure. Full article

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

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14 pages, 2584 KB

Open AccessArticle

Enhanced Catalytic Ozonation of Formaldehyde over MOFs- Derived MnO_x Catalysts with Diverse Morphologies: The Role of Oxygen Vacancies

by Yulin Sun, Yiwei Zhang, Yong He, Wubin Weng, Yanqun Zhu and Zhihua Wang

Catalysts 2025, 15(8), 752; https://doi.org/10.3390/catal15080752 - 6 Aug 2025

Viewed by 868

Abstract

Metal–organic frameworks (MOFs) have become a hot topic in various research fields nowadays. And MOF-derived metal oxides prepared by the sacrificial template method have been widely applied as catalysts for pollutant removal. Accordingly, we prepared a series of MOF-derived MnO_x catalysts with [...] Read more.

Metal–organic frameworks (MOFs) have become a hot topic in various research fields nowadays. And MOF-derived metal oxides prepared by the sacrificial template method have been widely applied as catalysts for pollutant removal. Accordingly, we prepared a series of MOF-derived MnO_x catalysts with diverse morphologies (rod-like, flower-like, slab-like) via the pyrolysis of MOF precursors, and the as-prepared MnO_x catalysts demonstrated superior performance compared to the one prepared using the co-precipitation method. MnO_x-II, with a flower-like structure, exhibited excellent activity for formaldehyde (HCHO) catalytic ozonation at room temperature, reaching complete HCHO conversion at O₃/HCHO of 1.5 and more than 90% CO₂ selectivity at an O₃/HCHO ratio of 2.5. On the basis of various characterization methods, it was clarified that the enhanced catalytic performance of MnO_x-II benefited from its larger BET surface area, abundant oxygen vacancies, better redox ability at lower temperature, and more Lewis acid sites. The H₂O resistance and stability tests were also conducted. Furthermore, DFT calculations substantiated the enhanced adsorption of HCHO and O₃ on oxygen vacancies, while in–situ DRIFTS measurements elucidated the degradation pathway of HCHO during catalytic ozonation through detected intermediates. Full article

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

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21 pages, 3418 KB

Open AccessArticle

Tunable Optical Bandgap and Enhanced Visible Light Photocatalytic Activity of ZnFe₂O₃-Doped ZIF-8 Composites for Sustainable Environmental Remediation

by Fatma Alharbi, Taymour Hamdalla, Hanan Al-Ghamdi, Badriah Albarzan and Ahmed Darwish

Catalysts 2025, 15(8), 720; https://doi.org/10.3390/catal15080720 - 29 Jul 2025

Viewed by 772

Abstract

Metal–organic frameworks (MOFs), particularly ZIF-8, have emerged as promising materials due to their high porosity, tunability, and chemical stability. In this study, we report the synthesis of ZnFe₂O₃-doped ZIF-8 composites with 10 wt% loading via a solvothermal method to [...] Read more.

Metal–organic frameworks (MOFs), particularly ZIF-8, have emerged as promising materials due to their high porosity, tunability, and chemical stability. In this study, we report the synthesis of ZnFe₂O₃-doped ZIF-8 composites with 10 wt% loading via a solvothermal method to enhance their optical and photocatalytic performance. Structural analyses confirmed the successful incorporation of ZnFe₂O₃ without disrupting the ZIF-8 framework. Optical studies revealed enhanced absorption in the visible range, a narrowed bandgap (4.26 eV vs. 4.37 eV for pristine ZIF-8), and an increased extinction coefficient, indicating superior light-harvesting potential. The photocatalytic activity was evaluated by methylene blue (MB) degradation under visible light, where the 10 wt% ZnFe₂O₃-ZIF-8 composite achieved 90% degradation efficiency, outperforming pristine ZIF-8 (67.8%). The catalyst also demonstrated excellent recyclability over five cycles and a proposed degradation mechanism involving ·OH and ·O₂⁻ radical formation. These findings demonstrate the potential of highly doped ZnFe₂O₃@ZIF-8 composites for environmental remediation and photonic applications. Full article

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

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17 pages, 3396 KB

Open AccessArticle

Morphological Regulation of Bi₅O₇I for Enhanced Efficiency of Rhodamine B Degradation Under Visible-Light

by Xi Yang, Jiahuali Lu, Lei Zhou, Qin Wang, Fan Wu, Yuwei Pan, Ming Zhang and Guangyu Wu

Catalysts 2025, 15(8), 714; https://doi.org/10.3390/catal15080714 - 26 Jul 2025

Cited by 2 | Viewed by 742

Abstract

Photocatalysis is considered to be a very promising method for the degradation of organic matter, because its process of degrading organic matter is safe. However, some problems such as weak absorption of visible light and electronic-hole recombination easily are obviously drawbacks. In this [...] Read more.

Photocatalysis is considered to be a very promising method for the degradation of organic matter, because its process of degrading organic matter is safe. However, some problems such as weak absorption of visible light and electronic-hole recombination easily are obviously drawbacks. In this paper, three different morphologies of Bi₅O₇I (nanoball, nanosheet, and nanotube) were successfully prepared by solvothermal method, which was used for the degradation of Rhodamine B (RhB). Comparing the photocatalytic effect of three different morphologies and concluding that the optimal morphology was the Bi₅O₇I nanoball (97.8% RhB degradation within 100 min), which was analysed by the characterisation tests. Free radical trapping experiments were tested, which revealed that the main roles in the degradation process were singlet oxygen (¹O₂) and holes (h⁺). The degradation pathways of RhB were analyzed in detail. The photo/electrochemical parts of the three materials were analysed and explained the degradation mechanism of RhB degradation. This investigate provides a very valuable guide for the development of multiple morphologies of bismuth-based photocatalysts for removing organic dyes in aquatic environment. Full article

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

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15 pages, 4061 KB

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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Review

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39 pages, 3987 KB

Open AccessReview

Ultrasonic-Assisted Fabrication of TiO₂-Based Composite Photocatalysts for Enhanced Photocatalysis of Organic Pollutants: A Review

by Jenny Hui Foong Chau, Ethan Dern Huang Kong, Jing Chang Chia, Chin Wei Lai, Joon Ching Juan, Yue Li, Ping Xiang, Irfan Anjum Badruddin and Amit Kumar

Catalysts 2025, 15(11), 1010; https://doi.org/10.3390/catal15111010 - 27 Oct 2025

Viewed by 525

Abstract

Water contamination and the global energy crisis are two of the most significant challenges in the world. Titanium dioxide (TiO₂) has garnered attention due to its promising photocatalytic performance. However, its wide band gap energy limits its efficiency under visible light [...] Read more.

Water contamination and the global energy crisis are two of the most significant challenges in the world. Titanium dioxide (TiO₂) has garnered attention due to its promising photocatalytic performance. However, its wide band gap energy limits its efficiency under visible light irradiation. To address this, TiO₂-based composite photocatalysts have been developed to narrow the band gap energy and suppress the recombination of electron–hole pairs, thereby enhancing photocatalytic performance. The ultrasonic technique, through acoustic cavitation, facilitates a synthetic process involving localized transient high-pressure and high-temperature conditions to produce photocatalysts with superior photocatalytic capabilities. This review focuses on ultrasonication and ultrasonic-assisted fabrication method for modifying TiO₂ into visible light-driven composite heterostructures. It discusses the parameters of ultrasonication that influence the synthesis and modification of these composites, along with the factors affecting photocatalytic performance. Full article

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

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27 pages, 2502 KB

Open AccessReview

Recent Advances in Transition Metal Dichalcogenide-Based Electrodes for Asymmetric Supercapacitors

by Tianyi Gao, Yue Li, Chin Wei Lai, Ping Xiang, Irfan Anjum Badruddin, Pooja Dhiman and Amit Kumar

Catalysts 2025, 15(10), 945; https://doi.org/10.3390/catal15100945 - 1 Oct 2025

Viewed by 777

Abstract

The global transition toward renewable energy sources has intensified in response to escalating environmental challenges. Nevertheless, the inherent intermittency and instability of renewable energy necessitate the development of reliable energy storage technologies. Supercapacitors are particularly notable for their high specific capacitance, rapid charge [...] Read more.

The global transition toward renewable energy sources has intensified in response to escalating environmental challenges. Nevertheless, the inherent intermittency and instability of renewable energy necessitate the development of reliable energy storage technologies. Supercapacitors are particularly notable for their high specific capacitance, rapid charge and discharge capability, and exceptional cycling stability. Concurrently, the increasing demand for efficient and sustainable energy storage systems has stimulated interest in multifunctional electrode materials that integrate electrocatalytic activity with electrochemical energy storage. Two-dimensional transition metal dichalcogenides (TMDs), owing to their distinctive layered structures, large surface areas, phase state, energy band structure, and intrinsic electrocatalytic properties, have emerged as promising candidates to achieve dual functionality in electrocatalysis and electrochemical energy storage for asymmetric supercapacitors (ASCs). Specifically, their unique electronic properties and catalytic characteristics promote reversible Faradaic reactions and accelerate charge transfer kinetics, thus markedly enhancing charge storage efficiency and energy density. This review highlights recent advances in TMD-based multifunctional electrodes. It elucidates mechanistic correlations between intrinsic electronic properties and electrocatalytic reactions that influence charge storage processes, guiding the rational design of high-performance ASC systems. Full article

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

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19 pages, 3220 KB

Open AccessFeature PaperReview

Integrated Technology of CO₂ Adsorption and Catalysis

by Mengzhao Li and Rui Wang

Catalysts 2025, 15(8), 745; https://doi.org/10.3390/catal15080745 - 5 Aug 2025

Viewed by 1147

Abstract

This paper discusses the integrated technology of CO₂ adsorption and catalysis, which combines adsorption and catalytic conversion, simplifies the traditional process, reduces energy consumption, and improves efficiency. The traditional carbon capture technology has the problems of high energy consumption, equipment corrosion, and [...] Read more.

This paper discusses the integrated technology of CO₂ adsorption and catalysis, which combines adsorption and catalytic conversion, simplifies the traditional process, reduces energy consumption, and improves efficiency. The traditional carbon capture technology has the problems of high energy consumption, equipment corrosion, and absorbent loss, while the integrated technology realizes the adsorption, conversion, and catalyst regeneration of CO₂ in a single reaction system, avoiding complex desorption steps. Through micropore confinement and surface electron transfer mechanism, the technology improves the reactant concentration and mass transfer efficiency, reduces the activation energy, and realizes the low-temperature and high-efficiency conversion of CO₂. In terms of materials, MOF-based composites, alkali metal modified oxides, and carbon-based hybrid materials show excellent performance, helping to efficiently adsorb and transform CO₂. However, the design and engineering of reactors still face challenges, such as the development of new moving bed reactors. This technology provides a new idea for CO₂ capture and resource utilization and has important environmental significance and broad application prospects. Full article

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

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