Catalysts

23 pages, 1789 KiB

Open AccessReview

Multi-Enzyme Synergy and Allosteric Regulation in the Shikimate Pathway: Biocatalytic Platforms for Industrial Applications

by Sara Khan and David D. Boehr

Catalysts 2025, 15(8), 718; https://doi.org/10.3390/catal15080718 - 28 Jul 2025

Abstract

The shikimate pathway is the fundamental metabolic route for aromatic amino acid biosynthesis in bacteria, plants, and fungi, but is absent in mammals. This review explores how multi-enzyme synergy and allosteric regulation coordinate metabolic flux through this pathway by focusing on three key [...] Read more.

The shikimate pathway is the fundamental metabolic route for aromatic amino acid biosynthesis in bacteria, plants, and fungi, but is absent in mammals. This review explores how multi-enzyme synergy and allosteric regulation coordinate metabolic flux through this pathway by focusing on three key enzymes: 3-deoxy-d-arabino-heptulosonate-7-phosphate synthase, chorismate mutase, and tryptophan synthase. We examine the structural diversity and distribution of these enzymes across evolutionary domains, highlighting conserved catalytic mechanisms alongside species-specific regulatory adaptations. The review covers directed evolution strategies that have transformed naturally regulated enzymes into standalone biocatalysts with enhanced activity and expanded substrate scope, enabling synthesis of non-canonical amino acids and complex organic molecules. Industrial applications demonstrate the pathway’s potential for sustainable production of pharmaceuticals, polymer precursors, and specialty chemicals through engineered microbial platforms. Additionally, we discuss the therapeutic potential of inhibitors targeting pathogenic organisms, particularly their mechanisms of action and antimicrobial efficacy. This comprehensive review establishes the shikimate pathway as a paradigmatic system where understanding allosteric networks enables the rational design of biocatalytic platforms, providing blueprints for biotechnological innovation and demonstrating how evolutionary constraints can be overcome through protein engineering to create superior industrial biocatalysts. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members (EBMs) in the Section "Biocatalysis")

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22 pages, 2808 KiB

Open AccessArticle

Assessment of Platinum Catalyst in Rice Husk Combustion: A Comparative Life Cycle Analysis with Conventional Methods

by Emmanuel Owoicho Abah, Pubudu D. Kahandage, Ryozo Noguchi, Tofael Ahamed, Paul Adigun and Christian Idogho

Catalysts 2025, 15(8), 717; https://doi.org/10.3390/catal15080717 - 28 Jul 2025

Abstract

This study presents a novel approach to address these challenges by introducing automobile platinum honeycomb catalysts into biomass combustion systems. The study employed a dual methodology, combining experimental investigations and a Life Cycle Assessment (LCA) case study, to comprehensively evaluate the catalyst’s performance [...] Read more.

This study presents a novel approach to address these challenges by introducing automobile platinum honeycomb catalysts into biomass combustion systems. The study employed a dual methodology, combining experimental investigations and a Life Cycle Assessment (LCA) case study, to comprehensively evaluate the catalyst’s performance and environmental impacts. The catalyst’s ability to facilitate combustion without open flame formation and its operational efficiency throughout combustion phases position it as a promising avenue for reducing gaseous and particulate matter emissions. The LCA considers multiple impact categories, employing the ReCiPe 2008 Hierarchist midpoint and endpoint perspective to assess environmental effects. The experimental results show that the catalyst effectively reduced CO, SO₂, and particulate emissions. Temperatures below 400 °C diminished the catalyst’s performance. The catalyst achieved a 100% CO conversion rate at specific temperatures of 427.4–490.3 °C. The findings highlight the potential for a 34% reduction in environmental impacts when replacing conventional rice husk combustion with the catalyst-integrated system. Notably, the study emphasizes the significance of sustainable catalyst manufacturing processes and cleaner electricity sources in maximizing environmental benefits. In conclusion, the integration of platinum honeycomb catalysts into biomass combustion systems, exemplified by rice husk combustion, emerges as a promising strategy for achieving more sustainable and environmentally friendly bioenergy production. Full article

(This article belongs to the Special Issue Catalytic Processes for a Green and Sustainable Future)

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30 pages, 7897 KiB

Open AccessFeature PaperReview

Recent Progress of 2D Pt-Group Metallic Electrocatalysts for Energy-Conversion Applications

by Ziyue Chen, Yuerong Wang, Haiyan He and Huajie Huang

Catalysts 2025, 15(8), 716; https://doi.org/10.3390/catal15080716 - 27 Jul 2025

Abstract

With the rapid growth of energy demand, the development of efficient energy-conversion technologies (e.g., water splitting, fuel cells, metal-air batteries, etc.) becomes an important way to circumvent the problems of fossil fuel depletion and environmental pollution, which motivates the pursuit of high-performance electrocatalysts [...] Read more.

With the rapid growth of energy demand, the development of efficient energy-conversion technologies (e.g., water splitting, fuel cells, metal-air batteries, etc.) becomes an important way to circumvent the problems of fossil fuel depletion and environmental pollution, which motivates the pursuit of high-performance electrocatalysts with controllable compositions and morphologies. Among them, two-dimensional (2D) Pt-group metallic electrocatalysts show a series of distinctive architectural merits, including a high surface-to-volume ratio, numerous unsaturated metal atoms, an ameliorative electronic structure, and abundant electron/ion transfers channels, thus holding great potential in realizing good selectivity, rapid kinetics, and high efficiency for various energy-conversion devices. Considering that great progress on this topic has been made in recent years, here we present a panoramic review of recent advancements in 2D Pt-group metallic nanocrystals, which covers diverse synthetic methods, structural analysis, and their applications as electrode catalysts for various energy-conversion technologies. At the end, the paper also outlines the research challenges and future opportunities in this emerging area. Full article

(This article belongs to the Special Issue Surface and Interface Engineering of Catalyst Nanostructures for Electrochemical Energy Conversion)

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20 pages, 10028 KiB

Open AccessArticle

The Fabrication of Cu₂O-u/g-C₃N₄ Heterojunction and Its Application in CO₂ Photoreduction

by Jiawei Lu, Yupeng Zhang, Fengxu Xiao, Zhikai Liu, Youran Li, Guiyang Shi and Hao Zhang

Catalysts 2025, 15(8), 715; https://doi.org/10.3390/catal15080715 - 27 Jul 2025

Abstract

Over efficient photocatalysts, CO₂ photoreduction typically converts CO₂ into low-carbon chemicals, which serve as raw materials for downstream synthesis processes. Here, an efficient composite photocatalyst heterojunction (Cu₂O-u/g-C₃N₄) has been fabricated to reduce CO₂. [...] Read more.

Over efficient photocatalysts, CO₂ photoreduction typically converts CO₂ into low-carbon chemicals, which serve as raw materials for downstream synthesis processes. Here, an efficient composite photocatalyst heterojunction (Cu₂O-u/g-C₃N₄) has been fabricated to reduce CO₂. Graphitic carbon nitride (g-C₃N₄) was synthesized via thermal polymerization of urea at 550 °C, while pre-dispersed Cu₂O derived from urea pyrolysis (Cu₂O-u) was prepared by thermal reduction of urea and CuCl₂·2H₂O at 180 °C. The heterojunction Cu₂O-u/g-C₃N₄ was subsequently constructed through hydrothermal treatment at 180 °C. This heterojunction exhibited a bandgap of 2.10 eV, with dual optical absorption edges at 485 nm and above 800 nm, enabling efficient harvesting of solar light. Under 175 W mercury lamp irradiation, the heterojunction catalyzed liquid-phase CO₂ photoreduction to formic acid, acetic acid, and methanol. Its formic acid production activity surpassed that of pristine g-C₃N₄ by 3.14-fold and TiO₂ by 8.72-fold. Reaction media, hole scavengers, and reaction duration modulated product selectivity. In acetonitrile/isopropanol systems, formic acid and acetic acid production reached 579.4 and 582.8 μmol·h⁻¹·g_cat⁻¹. Conversely, in water/triethanolamine systems, methanol production reached 3061.6 μmol·h⁻¹·g_cat⁻¹, with 94.79% of the initial conversion retained after three cycles. Finally, this work ends with the conclusions of the CO₂ photocatalytic reduction to formic acid, acetic acid, and methanol, and recommends prospects for future research. Full article

(This article belongs to the Section Photocatalysis)

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18 pages, 3396 KiB

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

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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13 pages, 1644 KiB

Open AccessArticle

Facile Synthesis of 4-(Methoxycarbonyl)phenyl 5-Arylfuran-2-Carboxylates via Readily Available Pd Catalyst–Their Thermodynamic, Spectroscopic Features and Nonlinear Optical Behavior

by Muhammad Fakhar U. Zaman, Adeel Mubarik, Aqsa Kanwal, Nasir Rasool, Matloob Ahmad, Maria Sohail, Ayesha Malik, Sami A. Al-Hussain and Magdi E. A. Zaki

Catalysts 2025, 15(8), 713; https://doi.org/10.3390/catal15080713 - 26 Jul 2025

Abstract

In this work, we described the synthesis of 4-(methoxycarbonyl)phenyl 5-bromofuran-2-carboxylate by reacting 5-bromofuroic acid with methylparaben in the incorporation of DCC/DMAP (Steglich esterification) as coupling agents. Later on, we subsequently synthesized a series of 4-(methoxycarbonyl)phenyl 5-aryl furan-2-carboxylates (5a–5e) through [...] Read more.

In this work, we described the synthesis of 4-(methoxycarbonyl)phenyl 5-bromofuran-2-carboxylate by reacting 5-bromofuroic acid with methylparaben in the incorporation of DCC/DMAP (Steglich esterification) as coupling agents. Later on, we subsequently synthesized a series of 4-(methoxycarbonyl)phenyl 5-aryl furan-2-carboxylates (5a–5e) through Suzuki coupling catalyzed by palladium (0) between 4-(methoxycarbonyl)phenyl 5-bromofuran-2-carboxylate (3) with several substituted arylated and heteroaryl boronic acids (4). DFT calculations were computed to elucidate electronic structural features of synthesized molecules (5a–5e) and to validate these findings by correlating with theoretical and experimental spectroscopic analysis. Furthermore, geometrical optimization, thermodynamic features, as FMO orbitals, MESP maps, NLO behavior and reactivity descriptors, were also determined from the PBE0 D3BJ/def2-TZVP/SMD_1,4-dioxane theory level to confirm the structural features of synthesized molecules. Full article

(This article belongs to the Special Issue Transition-Metal-Catalyzed Organic Synthesis)

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12 pages, 1803 KiB

Open AccessArticle

Valorization of Eggshell Powder as a Catalytic Activation Agent for Producing Porous Carbon Materials from Lignocellulosic Waste

by Chi-Hung Tsai, Hervan Marion Morgan, Jr. and Wen-Tien Tsai

Catalysts 2025, 15(8), 712; https://doi.org/10.3390/catal15080712 - 26 Jul 2025

Abstract

This study explored the potential of reusing eggshell powders as a renewable activating agent for producing porous carbon materials from coffee husk. Carbonization and activation experiments were conducted by heating the samples at a rate of 10 °C/min up to 850 °C under [...] Read more.

This study explored the potential of reusing eggshell powders as a renewable activating agent for producing porous carbon materials from coffee husk. Carbonization and activation experiments were conducted by heating the samples at a rate of 10 °C/min up to 850 °C under a nitrogen atmosphere. A custom-designed double steel-mesh sample holder was used to hold approximately 2.0 g coffee husk on the top, with varying masses of eggshell at the bottom to achieve eggshells to coffee husk mass ratios of 2:1, 4:1, 6:1 and 8:1. The results demonstrated that CO₂ released from the thermal decomposition of the eggshell powder significantly enhanced pore development at 850 °C. Compared to the pore properties of carbon material produced without eggshell (e.g., BET surface area of 321 m²/g), the activated carbon samples exhibited substantially improved pore properties (e.g., BET surface area in the range of 592 to 715 m²/g). Furthermore, the pore characteristics improved consistently with increasing eggshell content. Observations by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) confirmed the structural and chemical transformations of the resulting carbon materials. Under optimal carbonization-activation conditions, the resulting carbon materials derived from coffee husk exhibited microporous structures and slit-shaped pores, as indicated by the Type I isotherms and H4 hysteresis loops. Full article

(This article belongs to the Special Issue Catalytic Technologies for Solid Waste Management, Utilization, and Sustainability)

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15 pages, 4461 KiB

Open AccessReview

Cocatalyst-Tipped One-Dimensional Nanorods for Enhanced Photocatalytic Hydrogen Production

by Longlu Wang, Kun Wang, Junkang Sun, Chen Gu, Yixiang Luo and Shiyan Wang

Catalysts 2025, 15(8), 711; https://doi.org/10.3390/catal15080711 - 26 Jul 2025

Abstract

The controllable loading of a cocatalyst on a semiconductor is the key to further improving the efficiency and stability of visible-light photocatalytic hydrogen production. It is of great practical significance to load a cocatalyst onto a semiconductor spatially separated to realize space charge [...] Read more.

The controllable loading of a cocatalyst on a semiconductor is the key to further improving the efficiency and stability of visible-light photocatalytic hydrogen production. It is of great practical significance to load a cocatalyst onto a semiconductor spatially separated to realize space charge separation for efficient photocatalytic hydrogen evolution. The inherent anisotropic morphology of one-dimensional nanorods can provide two spatially separated locations at the tip and side surfaces of the nanorods. In this review, we systematically summarize non-centrosymmetric and centrosymmetric cocatalyst-tipped one-dimensional (1D) photocatalysts, including their preparation method, catalytic hydrogen production performance, and catalytic mechanism. This review will bring new vitality to the design, preparation, and application of cocatalyst-tipped one-dimensional nanorods. Full article

(This article belongs to the Section Photocatalysis)

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4 pages, 138 KiB

Open AccessEditorial

Environmentally Friendly Catalysts for Energy and Water Treatment Applications

by José Ignacio Lombraña, Hugo Olvera-Vargas and Sandra Yazmin Arzate Salgado

Catalysts 2025, 15(8), 710; https://doi.org/10.3390/catal15080710 - 25 Jul 2025

Abstract

Water and energy are two essential factors for the sustainable development of human activities, and are increasingly driven by continuous industrial growth and societal development [...] Full article

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

20 pages, 2630 KiB

Open AccessFeature PaperArticle

Experimental and Kinetic Modelling Study of the Heterogeneous Catalytic Conversion of Bioethanol into n-Butanol Using MgO–Al₂O₃ Mixed Oxide Catalyst

by Amosi Makoye, Anna Vikár, András Bence Nacsa, Róbert Barthos, József Valyon, Ferenc Lónyi and Tibor Nagy

Catalysts 2025, 15(8), 709; https://doi.org/10.3390/catal15080709 - 25 Jul 2025

Abstract

Ethanol upgrading via catalytic C–C coupling, commonly known as the Guerbet reaction, offers a sustainable route to produce 1-butanol, a high-performance biofuel. To address gaps in the mechanistic understanding of the catalytic reaction, we investigated the process involving a fixed-bed reactor, operated at [...] Read more.

Ethanol upgrading via catalytic C–C coupling, commonly known as the Guerbet reaction, offers a sustainable route to produce 1-butanol, a high-performance biofuel. To address gaps in the mechanistic understanding of the catalytic reaction, we investigated the process involving a fixed-bed reactor, operated at 275–325 °C, 21 bar, and weight hourly space velocities of 0.25–2.5 g_EtOH/(g_cat·h), using helium as a carrier gas, with a 5:1 He/EtOH molar ratio. The catalyst was a MgO–Al₂O₃ mixed oxide (Mg/Al = 2:1), derived from a hydrotalcite precursor. A detailed kinetic model was developed, encompassing 15 species and 27 reversible steps (10 sorption and 17 reaction steps), within a 1+1D sorption–reaction–transport framework. Four C₄-forming pathways were included: aldol condensation to form crotonaldehyde, semi-direct coupling to form butyraldehyde and crotyl alcohol, and direct coupling to form 1-butanol. To avoid overfitting, Arrhenius parameters were grouped by reaction type, resulting in sixty rate parameters and one active site-specific density parameter. The optimized model achieved high accuracy, with an average prediction error of 1.44 times the experimental standard deviation. The mechanistic analysis revealed aldol condensation as the dominant pathway below 335 °C, with semi-direct coupling to crotyl alcohol prevailing above 340 °C. The resulting model provides a robust framework for understanding and predicting complex reaction networks in ethanol upgrading systems. Full article

(This article belongs to the Special Issue Biomass Catalytic Conversion to Value-Added Chemicals)

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16 pages, 6618 KiB

Open AccessReview

N-Heterocyclic Carbene-Catalyzed Aerobic Oxidation of Aromatic Aldehydes into Carboxylic Acids: A Critical Review

by Alain Favre-Réguillon

Catalysts 2025, 15(8), 708; https://doi.org/10.3390/catal15080708 - 25 Jul 2025

Abstract

N-heterocyclic carbenes (NHCs) have demonstrated their versatility as catalysts for new activations and synthetic transformations of aldehydes. NHCs were originally applied in benzoin condensation and the Stetter reaction, while the development of new protocols under oxidative conditions has further expanded the potential of [...] Read more.

N-heterocyclic carbenes (NHCs) have demonstrated their versatility as catalysts for new activations and synthetic transformations of aldehydes. NHCs were originally applied in benzoin condensation and the Stetter reaction, while the development of new protocols under oxidative conditions has further expanded the potential of this methodology for the formation of carbon−carbon and carbon−heteroatom bonds. Among these reactions, NHCs are recognized as promising organocatalysts for the aerobic oxidation of aldehydes to carboxylic acids. However, to our knowledge, a comparison with other metal-free protocols has never been conducted. This review is intended to provide a perspective on aldehyde oxidation into the corresponding carboxylic acid catalyzed by NHCs, from its first practical description in 2009 until the beginning of 2025, and to compare it with other metal-free methods. Full article

(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)

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34 pages, 16124 KiB

Open AccessArticle

Molecular Dynamics Studies on the Inhibition of Cholinesterases by Secondary Metabolites

by Michael D. Gambardella, Yigui Wang and Jiongdong Pang

Catalysts 2025, 15(8), 707; https://doi.org/10.3390/catal15080707 - 25 Jul 2025

Abstract

The search for selective anticholinergic agents stems from varying cholinesterase levels as Alzheimer’s Disease progresses from the mid-to-late stage and from butyrylcholinesterase’s (BChE) role in β-amyloid plaque formation. While structure-based and pharmacophore-based virtual screening could search from large libraries in a short time, [...] Read more.

The search for selective anticholinergic agents stems from varying cholinesterase levels as Alzheimer’s Disease progresses from the mid-to-late stage and from butyrylcholinesterase’s (BChE) role in β-amyloid plaque formation. While structure-based and pharmacophore-based virtual screening could search from large libraries in a short time, these methods do not consider dynamic features that result from a ligand’s inhibition of the enzyme and consequently may under- or overexaggerate enzyme selectivity of a given ligand. In this computational study, we probed the selectivity of representative secondary metabolite compounds against acetylcholinesterase and BChE through molecular dynamics simulations. The results were evaluated by analysis of the root mean squared deviation of ligand heavy atoms, the radius of gyration of each inhibited and uninhibited enzyme, root mean squared fluctuation of residues, intermolecular interaction energy, and linear interaction energy approximation of the Gibbs free energy of binding. These considerations further reveal the induced-fit characteristics contributing to ChE selectivity that are predominantly due to the greater flexibility of BChE’s active site gorge. Full article

(This article belongs to the Special Issue Enzyme Catalysis: Innovations and Applications in Sustainable Chemistry)

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22 pages, 8896 KiB

Open AccessArticle

Synergistic Sequestration and Hydroxyapatite-Based Recovery of Phosphorus by the Coupling Process of CaCl₂/Modified Oyster Shell and Circulating Fluidized Bed Reactor

by Xuejun Long, Nanshan Yang, Huiqi Wang, Jun Fang, Rui Wang, Zhenxing Zhong, Peng Yu, Xuelian Xu, Hao Huang, Jun Wan, Xiejuan Lu and Xiaohui Wu

Catalysts 2025, 15(8), 706; https://doi.org/10.3390/catal15080706 - 24 Jul 2025

Abstract

A novel modified oyster shell (MOS-800) was developed to enhance phosphorus sequestration and recovery from wastewater. Approximately 33.3% of phosphate was eliminated by the MOS-800, which also exhibited excellent pH regulation capabilities. In semicontinuous tests, a synergistic phosphorus separation was achieved through the [...] Read more.

A novel modified oyster shell (MOS-800) was developed to enhance phosphorus sequestration and recovery from wastewater. Approximately 33.3% of phosphate was eliminated by the MOS-800, which also exhibited excellent pH regulation capabilities. In semicontinuous tests, a synergistic phosphorus separation was achieved through the coupling process of CaCl₂/MOS-800 and a circulating fluidized bed (CFB), resulting in an 86.5% phosphate separation. In continuous flow experiments, phosphorus elimination reached 98.2%. Material characterization revealed that hydroxyapatite (HAP) was the primary component of the crystallized products. Additionally, MOS-800 released 506.5–572.2 mg/g Ca²⁺ and 98.1 mg/g OH⁻. A four-stage heterogeneous crystallization mechanism was proposed for the coupling process. In the first stage, Ca²⁺ quickly reacted with phosphate to form Ca-P ion clusters, etc. In the second stage, these clusters packed randomly to form spherical amorphous calcium phosphate (ACP). In the third stage, the ACP spheres were transformed and rearranged into sheet-like HAP crystallites, Finally, in the fourth stage, the HAP crystallites aggregated on the surface of crystal seeds, also with the addition of crystal seeds and undissolved MOS-800, potentially catalyzing the heterogeneous crystallization. These findings suggest that the CaCl₂/MOS-800/CFB system is a promising technique for phosphate recovery from wastewater. Full article

(This article belongs to the Special Issue Nanocatalysts for the Degradation of Refractory Pollutants, 2nd Edition)

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12 pages, 4589 KiB

Open AccessArticle

Unveiling the Photocatalytic Behavior of PNTP on Au-Ag Alloy Nanoshells Through SERS

by Wenpeng Yang, Wenguang Geng, Xiyuan Lu, Lihua Qian, Shijun Luo, Lei Xu, Yu Shi, Tengda Song and Mengyang Li

Catalysts 2025, 15(8), 705; https://doi.org/10.3390/catal15080705 - 24 Jul 2025

Abstract

Au-Ag alloy nanoshells (ANSs) were synthesized via chemical reduction, exhibiting superior plasmonic photocatalytic performance. TEM revealed uniform hollow structures (~80 nm), while EDS mapping confirmed homogeneous Au-Ag distribution throughout the shell. According to EDX analysis, the alloy contained 71.40% Ag by weight. XRD [...] Read more.

Au-Ag alloy nanoshells (ANSs) were synthesized via chemical reduction, exhibiting superior plasmonic photocatalytic performance. TEM revealed uniform hollow structures (~80 nm), while EDS mapping confirmed homogeneous Au-Ag distribution throughout the shell. According to EDX analysis, the alloy contained 71.40% Ag by weight. XRD verified the formation of a substitutional solid solution without phase separation. The photocatalytic activity was evaluated using p-nitrothiophenol (PNTP) to 4,4′-dimercapto-azobenzene (DMAB) conversion monitored by SERS. UV-Vis spectroscopy showed LSPR peaks of ANSs between Au and Ag NPs, confirming effective alloying. Kinetic studies revealed that ANSs exhibited reaction rates 250–351 times higher than those of Au NPs and 5–10 times higher than those of Ag NPs. This resulted from the synergistic catalysis of Au-Ag and enhanced electromagnetic fields. ANSs demonstrated dual functionality as SERS substrates and photocatalysts, providing a foundation for developing multifunctional nanocatalytic materials. Full article

(This article belongs to the Section Photocatalysis)

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16 pages, 4134 KiB

Open AccessArticle

Effect of Oxygen-Containing Functional Groups on the Performance of Palladium/Carbon Catalysts for Electrocatalytic Oxidation of Methanol

by Hanqiao Xu, Hongwei Li, Xin An, Weiping Li, Rong Liu, Xinhong Zhao and Guixian Li

Catalysts 2025, 15(8), 704; https://doi.org/10.3390/catal15080704 - 24 Jul 2025

Abstract

The methanol oxidation reaction (MOR) of direct methanol fuel cells (DMFCs) is limited by the slow kinetic process and high reaction energy barrier, significantly restricting the commercial application of DMFCs. Therefore, developing MOR catalysts with high activity and stability is very important. In [...] Read more.

The methanol oxidation reaction (MOR) of direct methanol fuel cells (DMFCs) is limited by the slow kinetic process and high reaction energy barrier, significantly restricting the commercial application of DMFCs. Therefore, developing MOR catalysts with high activity and stability is very important. In this paper, oxygen-functionalised activated carbon (FAC) with controllable oxygen-containing functional groups was prepared by adjusting the volume ratio of H₂SO₃/HNO₃ mixed acid, and Pd/AC and Pd/FAC catalysts were synthesised via the hydrazine hydrate reduction method. A series of characterisation techniques and electrochemical performance tests were used to study the catalyst. The results showed that when V(H₂SO₃):V(HNO₃) = 2:3, more defects were generated on the surface of the AC, and more oxygen-containing functional groups represented by C=O and C–OH were attached to the surface of the support, which increased the anchor sites of Pd and improved the dispersion of Pd nanoparticles (Pd NPs) on the support. At the same time, the mass–specific activity of Pd/FAC for MOR was 2320 mA·mg_Pd, which is 1.5 times that of Pd/AC, and the stability was also improved to a certain extent. In situ infrared spectroscopy further confirmed that oxygen functionalisation treatment promoted the formation and transformation of *COOH intermediates, accelerated the transformation of CO_L into CO_B, reduced the poisoning of CO_ads species adsorbed to the catalyst, optimised the reaction path and improved the catalytic kinetic performance. Full article

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16 pages, 1382 KiB

Open AccessFeature PaperArticle

The Catalytic Consequence of Isolated Ni Single-Atoms in BEA Zeolite for Hydrogen Production and Olefin Conversion

by Yitong Zhao, Meng Liu, Yao Ning, Ying Zhang and Zhijie Wu

Catalysts 2025, 15(8), 703; https://doi.org/10.3390/catal15080703 - 24 Jul 2025

Abstract

In our previous work, we fabricated Ni single-atoms within Beta zeolite (Ni₁@Beta-NO₃⁻) using NiNO₃·6H₂O as a metal precursor without any chelating agents, which exhibited exceptional performance in the selective hydrogenation of furfural. Owing to [...] Read more.

In our previous work, we fabricated Ni single-atoms within Beta zeolite (Ni₁@Beta-NO₃⁻) using NiNO₃·6H₂O as a metal precursor without any chelating agents, which exhibited exceptional performance in the selective hydrogenation of furfural. Owing to the confinement effect, the as-encapsulated nickel species appears in the form of Ni⁰ and Ni^δ+, which implies its feasibility in metal catalysis and coordination catalysis. In the study reported herein, we further explored the hydrogen production and olefin oligomerization performance of Ni₁@Beta-NO₃⁻. It was found that Ni₁@Beta-NO₃⁻ demonstrated a high H₂ generation turnover frequency (TOF) and low activation energy (E_a) in a sodium borohydride (NaBH₄) hydrolysis reaction, with values of 331 min⁻¹ and 30.1 kJ/mol, respectively. In ethylene dimerization, it exhibited a high butylene selectivity of 99.4% and a TOF as high as 5804 h⁻¹. In propylene oligomerization, Ni₁@Beta-NO₃⁻ demonstrated high selectivity (75.21%) of long-chain olefins (≥C₆⁺), overcoming the problem of cracking reactions that occur during oligomerization using H-Beta. Additionally, as a comparison, the influence of the metal precursor (NiCl₂) on the performance of the encapsulated Ni catalyst was also examined. This research expands the application scenarios of non-noble metal single-atom catalysts and provides significant assistance and potential for the production of H₂ from hydrogen storage materials and the production of valuable chemicals. Full article

(This article belongs to the Special Issue State of the Art and Future Challenges in Zeolite Catalysts)

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17 pages, 3269 KiB

Open AccessFeature PaperArticle

Microwave-Assisted Degradation of Azo Dyes Using NiO Catalysts

by Celinia de Carvalho Chan, Lamiaa F. Alsalem, Mshaal Almalki, Irina Bozhinovska, James S. Hayward, Stephen S. N. Williams and Jonathan K. Bartley

Catalysts 2025, 15(8), 702; https://doi.org/10.3390/catal15080702 - 24 Jul 2025

Abstract

Catalysts are ubiquitous in manufacturing industries and gas phase pollutant abatement but are not widely used in wastewater treatment, as high temperatures and concentrated waste streams are needed to achieve the reaction degradation rates required. Heating water is energy intensive, and alternative, low [...] Read more.

Catalysts are ubiquitous in manufacturing industries and gas phase pollutant abatement but are not widely used in wastewater treatment, as high temperatures and concentrated waste streams are needed to achieve the reaction degradation rates required. Heating water is energy intensive, and alternative, low temperature solutions have been investigated, collectively known as advanced oxidation processes. However, many of these advanced oxidation processes use expensive oxidants such as perchlorate, hydroxy radicals or ozone to react with contaminants, and therefore have high running costs. This study has investigated microwave catalysis as a low-energy, low-cost technology for water treatment using NiO catalysts that can be heated in the microwave field to drive the decomposition of azo-dye contaminants. Using this methodology for the microwave-assisted degradation of two azo dyes (azorubine and methyl orange), conversions of >95% were achieved in only 10 s with 100 W microwave power. Full article

(This article belongs to the Special Issue Advances in Microwave-Assisted Catalysis: From Catalytic Materials to Catalytic Reactions)

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22 pages, 5670 KiB

Open AccessArticle

Tailoring TiO₂/TiN Bi-Layer Interfaces via Nitrogen Diffusion and Gold Functionalization for Advanced Photocatalysis

by Jelena P. Georgijević, Tijana Stamenković, Tijana Đorđević, Danilo Kisić, Vladimir Rajić and Dejan Pjević

Catalysts 2025, 15(8), 701; https://doi.org/10.3390/catal15080701 - 23 Jul 2025

Abstract

100 nm thick TiO₂/TiN bilayers with varying thickness ratios were deposited via reactive sputtering of a Ti target in controlled oxygen and nitrogen atmospheres. Post-deposition annealing in air at 600 °C was performed to induce nitrogen diffusion through the oxygen-deficient TiO [...] Read more.

100 nm thick TiO₂/TiN bilayers with varying thickness ratios were deposited via reactive sputtering of a Ti target in controlled oxygen and nitrogen atmospheres. Post-deposition annealing in air at 600 °C was performed to induce nitrogen diffusion through the oxygen-deficient TiO₂ layer. The resulting changes in morphology and chemical environment were investigated in detail using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and UV-Vis spectroscopy. Detailed TEM and XPS analyses have confirmed nitrogen diffusion across the TiO₂ layer, with surface nitrogen concentration and the ratio of interstitial to substitutional nitrogen dependent on the TiO₂/TiN mass ratio. Optical studies demonstrated modifications in optical constants and a reduction of the effective bandgap from 3.2 eV to 2.6 eV due to new energy states introduced by nitrogen doping. Changes in surface free energy induced by nitrogen incorporation showed a correlation to nitrogen doping sites on the surface, which had positive effects on overall photocatalytic activity. Photocatalytic activity, assessed through methylene blue degradation, showed enhancement attributed to nitrogen doping. Additionally, deposition of a 5 nm gold layer on the annealed sample enabled investigation of synergistic effects between nitrogen doping and gold incorporation, resulting in further improved photocatalytic performance. These findings establish the TiO₂/TiN bilayer as a versatile platform for supporting thin gold films with enhanced photocatalytic properties. Full article

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

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9 pages, 798 KiB

Open AccessArticle

Mechanistic Behavior of Basicity of Bimetallic Ni/ZrO₂ Mixed Oxides for Stable Oxythermal Reforming of CH₄ with CO₂

by Hyuk Jong Bong, Nagireddy Gari Subba Reddy and A. Geetha Bhavani

Catalysts 2025, 15(8), 700; https://doi.org/10.3390/catal15080700 - 22 Jul 2025

Abstract

The mixed oxides of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and Ni-Ba-Ca/ZrO₂ were prepared using the co-precipitation method at a pH of precisely 8.3. The catalytic mixed oxides of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and [...] Read more.

The mixed oxides of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and Ni-Ba-Ca/ZrO₂ were prepared using the co-precipitation method at a pH of precisely 8.3. The catalytic mixed oxides of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and Ni-Ba-Ca/ZrO₂ were characterized using x-ray diffraction XRD, Brunauer Emmett Teller (BET), scanning electron microscopy (SEM), and metal dispersion for the screening of phase purity, surface area, and morphology. The mixed oxides are subjected to CO₂-TPD to quantify the basicity of every composition. The mixed oxide catalysts of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and Ni-Ba-Ca/ZrO₂ were screened for oxythermal reforming of CH₄ with CO₂ in a fixed bed tubular reactor at 800 °C. Among all catalysts, the Ba- and Ca- loaded Ni-Ba-Ca/ZrO₂ showed high conversion by the decomposition of methane and CO₂ disproportionation throughout the time on stream of 29 h. The high activity with stability led to less coke formation over Ni-Ba-Ca/ZrO₂ over the surface. The stable syngas production with an active catalyst bed contributed to the improved bimetallic synergy. The high surface basicity of Ni-Ba-Ca/ZrO₂ may keep actively gasifying the formed soot and allow for further stable reforming reactions. 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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