Catalysts

12 pages, 7868 KB

Open AccessArticle

Surprising Tribocatalytic Production of H₂ from H₂O by Silicon Single Crystals via Low-Speed Magnetic Stirring

by Jianqing Zhou, Xiaodong Cui, Jie Zhang, Senhua Ke, Linfeng Fei, Lun Yang and Wanping Chen

Catalysts 2026, 16(6), 523; https://doi.org/10.3390/catal16060523 (registering DOI) - 5 Jun 2026

Abstract

A surprising tribocatalytic capability has been discovered for Si single crystals to convert mechanical energy into chemical energy for organic dye degradation recently. In this study, their tribocatalytic capability has been explored for converting mechanical energy into chemical energy of water splitting. In [...] Read more.

A surprising tribocatalytic capability has been discovered for Si single crystals to convert mechanical energy into chemical energy for organic dye degradation recently. In this study, their tribocatalytic capability has been explored for converting mechanical energy into chemical energy of water splitting. In glass reactors with Si single crystals coated on the bottoms and with H₂O and N₂ enclosed, Al₂O₃ nanoparticles, TiO₂ nanoparticles, and NiO particles were stimulated through magnetic stirring using home-made PTFE magnetic rotary disks separately. For Al₂O₃ nanoparticles, as much as 14,330 and 41,964 ppm H₂ were produced after 1 and 3 h of 400 rpm magnetic stirring, respectively, much higher than those obtained for TiO₂ and NiO, and for Al₂O₃ nanoparticles in glass-bottomed reactors as well. The tribocatalytic production of H₂ was further explored with respect to NaCl addition to H₂O and p/n doping in Si, with negative effects observed for them all. Photoluminescence spectroscopy revealed continuous generation of hydroxyl radicals in the course of magnetic stirring, which supports a tribocatalytic mechanism based on the excitation of electron–hole pairs in Si single crystals through mechanical energy absorbed through friction. These findings suggest a great potential for narrow-band semiconductors to utilize mechanical energy through friction to carry out important chemical reactions. Full article

(This article belongs to the Special Issue Tribocatalytic Utilization of Mechanical Energy by Materials and Technologies for Energy and Environmental Challenges)

► Show Figures

Figure 1

29 pages, 4456 KB

Open AccessReview

Recovery of V₂O₅ from Spent Vanadium Catalysts: Materials Insights into Deactivation and Recycling Strategies

by Sebastian Drużyński, Adriana Wróbel-Kaszanek, Bartłomiej Igliński, Urszula Kiełkowska and Krzysztof Mazurek

Catalysts 2026, 16(6), 522; https://doi.org/10.3390/catal16060522 (registering DOI) - 5 Jun 2026

Abstract

The growing demand for vanadium and the environmental threat associated with spent catalyst masses have sparked widespread scientific interest in the recovery of V₂O₅ from deactivated vanadium-based catalysts, including those used in sulphuric(VI) acid production. This review places vanadium(V) recovery [...] Read more.

The growing demand for vanadium and the environmental threat associated with spent catalyst masses have sparked widespread scientific interest in the recovery of V₂O₅ from deactivated vanadium-based catalysts, including those used in sulphuric(VI) acid production. This review places vanadium(V) recovery in the broader context of resource efficiency and the circular economy. The main deactivation mechanisms are analysed, including poisoning, sintering, and structural changes affecting catalytic activity and vanadium availability. Hydrometallurgical approaches to vanadium recovery are discussed, with a particular focus on leaching agents, vanadium speciation in aqueous media, and subsequent separation techniques such as adsorption, solvent extraction, and vanadium(V) precipitation. Key process parameters influencing recovery efficiency, including temperature, pH, and caustic composition, are discussed to provide a comparative assessment of existing methods. The analysis highlights the advantages and limitations of current recovery methods and identifies gaps related to selectivity, process integration, and environmental impact. Overall, the study demonstrates that effective V₂O₅ recovery requires a thorough understanding of catalyst deactivation and solution chemistry. It also outlines models for developing more sustainable and economically viable recycling strategies. Full article

(This article belongs to the Section Industrial Catalysis)

► Show Figures

Figure 1

19 pages, 2061 KB

Open AccessArticle

Kinetic, Computational and Mechanistic Investigation of [Rh(κ²-dppe)₂]-Catalyzed Transfer Hydroformylation of Alkenes with Formaldehyde Assisted by Bayesian Parameter Estimation

by Merlín Rosales, Federico Arrieta and Juan Carlos Drosos-Ramirez

Catalysts 2026, 16(6), 521; https://doi.org/10.3390/catal16060521 (registering DOI) - 5 Jun 2026

Abstract

Transfer hydroformylation of alkenes with formaldehyde constitutes a green and sustainable route to aldehydes. In this work, the transfer hydroformylation of styrene with formaldehyde was efficiently catalyzed by [Rh(κ²-dppe)₂]⁺ (A), where dppe stands for 1,2-bis(diphenylphosphino)ethane. [...] Read more.

Transfer hydroformylation of alkenes with formaldehyde constitutes a green and sustainable route to aldehydes. In this work, the transfer hydroformylation of styrene with formaldehyde was efficiently catalyzed by [Rh(κ²-dppe)₂]⁺ (A), where dppe stands for 1,2-bis(diphenylphosphino)ethane. The reaction was found to be first order with respect to both Rh and substrate concentrations and fractional order with respect to formaldehyde concentration, in line with the behavior previously reported for 1-hexene. DFT was used to investigate the reaction mechanism by using ethene and [Rh(κ²-dpe)₂]⁺ (A), where dpe stands for 1,2-bis(phosphine)ethane, as simplified models of the substrate and catalyst, respectively, and by considering several functionals. The DFT calculations indicate that M06-L provides the most suitable description of the thermodynamic and activation parameters associated with the elementary steps. The combined analysis of kinetic results and the DFT calculations allowed us to propose a detailed catalytic cycle for this reaction, initiated by the reversible oxidative addition of formaldehyde to complex A to afford [Rh(H)(CHO)(κ²-dppe)₂]⁺ (B,

K_{1}

). Coordination of ethene occurs through partial dissociation of one phosphorus atom of the diphosphine ligand, generating [Rh(H)(alkene)(CHO)(κ²-dppe)(κ¹-dppe)]⁺ (I_B,

K_{2}

), followed by the transfer of the hydride to the alkene to give [Rh(alkyl)(CHO)(κ²-dppe)₂]⁺ (C,

k_{3}

), which is considered the rate-determining step of the process. The cycle is completed by reductive elimination of propanal, thereby regenerating A. The overall activation energy calculated by DFT (Ea = 20.0 kcal mol⁻¹) is in good agreement with the experimental values determined for 1-hexene and styrene (20.1 and 22.9 kcal mol⁻¹, respectively). On the basis of these experimental and DFT results, a mathematical kinetic model with the canonical form

r_{0} = {K_{1} K_{2} k}_{3} {[R h]}_{o} [a l k e n e] [C H_{2} O] / ({1 + K}_{1} [C H_{2} O])

was developed and fitted using a tandem LMFit/Bayesian approach, allowing the values of K₁ and K₂k₃ to be estimated, with comparatively low uncertainty. Overall, this integrated kinetic, computational, and statistical study provides a consistent mechanistic and quantitative framework for understanding the transfer hydroformylation of alkenes with formaldehyde. Full article

► Show Figures

Figure 1

19 pages, 3956 KB

Open AccessArticle

Research on the Activation of Persulfate for Antibiotic Degradation by Iron–Nitrogen Doped Biochar

by Zhihao Chen, Jiaxuan Zuo, Daimei Chen, Yilei Li and Guofang Du

Catalysts 2026, 16(6), 520; https://doi.org/10.3390/catal16060520 - 4 Jun 2026

Abstract

Carbamazepine (CBZ), a poorly biodegradable antibiotic, is widely detected in aquatic environments, posing potential threats to ecosystems and human health. There is an urgent need to develop efficient water treatment technologies. This study successfully prepared nitrogen-doped biochar composite materials loaded with zero-valent iron [...] Read more.

Carbamazepine (CBZ), a poorly biodegradable antibiotic, is widely detected in aquatic environments, posing potential threats to ecosystems and human health. There is an urgent need to develop efficient water treatment technologies. This study successfully prepared nitrogen-doped biochar composite materials loaded with zero-valent iron (Fe⁰@CN) via a one-pot calcination method for activating peroxymonosulfate (PMS) to degrade CBZ. The material was systematically characterized using multiple analytical techniques. Results indicate that Fe⁰@CN-1.5 exhibits a high specific surface area (482.65 m²/g) and an abundant mesoporous structure, with nitrogen doping promoting graphitic structure formation and the uniform dispersion of zero-valent iron. Under conditions of a 0.3 g/L catalyst loading, a 15 mM PMS concentration, and an initial pH of 5.5, 30 mg/L of CBZ achieved 97% degradation within 30 min. Radical quenching experiments and electrochemical analysis indicate that ·SO₄⁻ and ·OH are the primary active species in this system, alongside non-radical electron transfer processes. The material demonstrates excellent degradation performance and cycling stability across various real-world water bodies and pollutant systems. This study provides a carbon-based catalytic material with application potential and a theoretical basis for the efficient treatment of antibiotic wastewater. Full article

(This article belongs to the Special Issue Two-Dimensional Materials in Photo(electro)catalysis, 2nd Edition)

► Show Figures

Graphical abstract

15 pages, 11419 KB

Open AccessArticle

Highly Active and Stable TiO₂{001}-Supported Palladium Catalyst for CO Oxidation in Complex Atmospheres

by Mengyin Chen, Rongwei Shi, Ziyun Chen, Rui Cai, Yubing Liu, Yining Fan and Bolian Xu

Catalysts 2026, 16(6), 519; https://doi.org/10.3390/catal16060519 - 4 Jun 2026

Abstract

Catalytic oxidation has become a crucial technology for removing CO from industrial flue gas. However, the complex composition of flue gas (including NH₃, NO, SO₂, H₂O, etc.) poses significant challenges to the catalytic activity and stability of [...] Read more.

Catalytic oxidation has become a crucial technology for removing CO from industrial flue gas. However, the complex composition of flue gas (including NH₃, NO, SO₂, H₂O, etc.) poses significant challenges to the catalytic activity and stability of catalysts. In this work, we propose a new strategy for constructing highly efficient catalysts by loading a Pd component onto TiO₂ nanosheets (NSs) with predominantly exposed {001} facets. It has been revealed that the well-connected channels, abundant oxygen vacancies and Ti³⁺ species on the TiO₂(NS) support facilitate the formation of highly dispersed and electron-rich Pd nanoparticles. The weak adsorption of impurities such as NH₃, SO₂, NO and H₂O on these active sites promotes the adsorption and activation of the target reactants (CO and O₂), thereby enhancing catalytic activity. Furthermore, such reduced adsorption inhibits the aggregation of Pd nanoparticles and synergizes with the intrinsically weak NH₃ adsorption of TiO₂(NS) to suppress ammonium sulfate species deposition, thereby enhancing long-term catalytic stability. This work advances TiO₂ facet engineering in catalysis and offers new design concepts for efficient CO oxidation catalysts in complex atmospheres. Full article

► Show Figures

Graphical abstract

14 pages, 6081 KB

Open AccessArticle

A New Composite Lead Electrode for the Reduction Synthesis of Adiponitrile from Acrylonitrile

by Jiaqi Fu, Yi Li, Yuxiang Xu, Peilan Ma, Fengcai Li, Yonggang Sun and Song Chen

Catalysts 2026, 16(6), 518; https://doi.org/10.3390/catal16060518 - 4 Jun 2026

Abstract

Adiponitrile (ADN) serves as a critical intermediate for manufacturing polyamide 66. Electrochemical hydrodimerization of acrylonitrile (AN) offers a green and sustainable route for ADN production, yet conventional lead plate cathodes still suffer from high cell voltage, insufficient mechanical stability, and lead dust shedding [...] Read more.

Adiponitrile (ADN) serves as a critical intermediate for manufacturing polyamide 66. Electrochemical hydrodimerization of acrylonitrile (AN) offers a green and sustainable route for ADN production, yet conventional lead plate cathodes still suffer from high cell voltage, insufficient mechanical stability, and lead dust shedding during long-term operation. In this work, we developed a novel composite lead electrode in ambient air to overcome these drawbacks. Key preparation parameters, including calcination temperature, polytetrafluoroethylene (PTFE) content, substrate type, dispersion method, and dispersant dosage, were carefully screened and optimized. The optimal conditions were determined as follows: PTFE mesh as the substrate, 10% PTFE relative to lead powder, mechanical stirring dispersion, 0.5 wt% sodium hexametaphosphate as dispersant, air calcination at 325 °C, and subsequent electrochemical reduction. SEM, XRD, and XPS characterizations showed that the optimized electrode features a three-dimensional porous network assembled from interlaced rod-like and flower-like micro/nanostructures, which greatly elevates the specific surface area, enriches active sites, and facilitates electrolyte penetration and mass transport. After electrochemical reduction, the electrode surface was dominated by catalytically active Pb⁰. Electrochemical tests indicated that the composite electrode delivered a current density of 60–70 mA·cm⁻² at −1.6 to −2.0 V (vs. SCE) for AN reduction, nearly three times higher than that of a conventional lead plate. In addition, the composite electrode showed improved mechanical hardness and completely suppressed lead dust shedding, greatly enhancing operational safety and service life. Stable voltage was maintained during long-term electrolysis. This study provides a low-cost and scalable strategy for fabricating high-performance lead-based composite cathodes, which can support the industrial-scale green electrosynthesis of adiponitrile from acrylonitrile. Full article

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

► Show Figures

Figure 1

20 pages, 4802 KB

Open AccessArticle

Study on the Synthesis of Micron-Sized Plate-like TS-1 Using Sodium Persulfate as a Morphology-Regulating Additive

by Shengjie Zhu, Xiaomin Zhang, Lei Dong, Yangyang Yuan, Xiuyun Ma and Lei Xu

Catalysts 2026, 16(6), 517; https://doi.org/10.3390/catal16060517 - 3 Jun 2026

Abstract

Micron-sized plate-like TS-1 zeolites are designed to combine the mass transfer efficiency of MFI straight channels along the b-axis by maximizing the exposure of these channel openings on the a-c crystal surface with the recoverability advantage of micrometer-scale crystals. In this study, micron-sized [...] Read more.

Micron-sized plate-like TS-1 zeolites are designed to combine the mass transfer efficiency of MFI straight channels along the b-axis by maximizing the exposure of these channel openings on the a-c crystal surface with the recoverability advantage of micrometer-scale crystals. In this study, micron-sized plate-like TS-1 was successfully synthesized by introducing sodium persulfate (Na₂S₂O₈) as an inorganic morphology-regulating additive. Through comparative experiments with ammonium persulfate, potassium persulfate, sodium carbonate, and sodium sulfate, the regulatory role of persulfate anion (S₂O₈²⁻), rather than the sodium cation, was identified. By varying the Na₂S₂O₈/SiO₂ molar ratio from 0.03 to 0.07, plate-like crystals with a- and c-axis dimensions in the micrometer range and b-axis thickness of 400–1100 nm were obtained. This morphology-regulation strategy was shown to be universal in both steam-assisted crystallization (SAC) and hydrothermal synthesis methods. Furthermore, post-treatment with tetrapropylammonium hydroxide (TPAOH) was applied to introduce additional textural porosity and construct a hierarchical pore structure. The optimized sample (TS-1-0.06SP-HT-P) achieved a total surface area of 444 m² g⁻¹ and a pore volume of 0.28 cm³ g⁻¹. The catalytic performance of the hierarchically porous samples was evaluated using 1-hexene epoxidation and phenol hydroxylation as model reactions. Catalytic stability tests using phenol hydroxylation (cat. 300 mg, phenol 36 mmol, n(phenol):n(H₂O₂) = 2, H₂O 4 mL, 353 K, 1 h) showed that TS-1-0.06SP-HT-P maintained stable performance over five consecutive cycles, with phenol conversion remaining at 20.8–22.3% and hydroquinone plus catechol selectivity at 73.0–78.1%. This work provides a feasible approach for the plate-like morphology regulation and performance optimization of TS-1 zeolites. Full article

(This article belongs to the Section Catalytic Materials)

► Show Figures

Figure 1

17 pages, 12033 KB

Open AccessArticle

Nanobiocatalysts Based on Protease Conjugates with Carboxylated Multi-Walled Carbon Nanotubes for Combating Bacterial Biofilms

by Yuliya Maksimova, Aleksandra Pankova and Aleksandr Maksimov

Catalysts 2026, 16(6), 516; https://doi.org/10.3390/catal16060516 - 3 Jun 2026

Abstract

The use of hydrolytic enzymes is one of the most promising methods for combating bacterial biofilms. However, the use of native enzymes is limited by the rapid loss of activity under unfavorable conditions. Immobilization of enzymes on carbon nanoparticles enhances their stability, allows [...] Read more.

The use of hydrolytic enzymes is one of the most promising methods for combating bacterial biofilms. However, the use of native enzymes is limited by the rapid loss of activity under unfavorable conditions. Immobilization of enzymes on carbon nanoparticles enhances their stability, allows for biocatalyst reuse, and creates a synergistic effect due to the intrinsic antimicrobial properties of the nanomaterials. The aim of this investigation was to create and comparatively analyze conjugates of acid and alkaline proteases with carboxylated multiwalled carbon nanotubes (MWCNTs-COOH) and to assess their effect on the formation and destruction of E. coli VKM B-3858D biofilms. The immobilization efficiency and kinetics of enzyme adsorption on the support were quantified by determining the protein concentration using the Bradford assay. The morphology and dispersion of the resulting conjugates were analyzed using atomic force microscopy (AFM). Protease activity was determined by a modified Anson method using the Folin–Ciocalteu reagent. Biofilm biomass was determined using crystal violet staining. The binding efficiency of the acid protease to MWCNTs-COOH was shown to reach 93%, which is significantly higher than that of the alkaline protease. The highest degree of immobilization was observed at a protein concentration of 117–338 μg/mL (10–20 mg/mL of the enzyme preparations). The interaction of the acid protease with the carbon nanoparticles increased dispersion, reducing the size of aggregates from ~1 μm to ~68 nm. As a result, acid protease conjugates with MWCNTs-COOH significantly reduced the biofilm biomass compared to both the enzyme-free control and the native enzyme. Alkaline protease, unlike the acid protease, destroys mature biofilms, and immobilization on MWCNTs-COOH enhances this ability. Native alkaline protease and acid protease conjugates with MWCNTs-COOH are effective in combating the biofilm formation of Gram-negative bacteria, while alkaline protease conjugates are suitable for disrupting mature biofilms. Full article

(This article belongs to the Section Biocatalysis)

► Show Figures

Figure 1

9 pages, 1731 KB

Open AccessArticle

Effect of NiFe Alloy Exsolution from LSFNO Surface on RWGS Reaction in CO₂/H₂O Co-Electrolysis Investigated by DFT Charge Analysis

by Sijie He, Zilin Zhou, Junbo Wang, Qi Tang, Yin Zhang, Jingze Liu, Zixuan Zhang, Lei Fu and Yang Wang

Catalysts 2026, 16(6), 515; https://doi.org/10.3390/catal16060515 - 3 Jun 2026

Abstract

The electrochemical co-conversion of CO₂ and H₂O into valuable products is a promising approach toward carbon-neutral energy systems. Alloy exsolution from perovskite lattices has emerged as an effective strategy to engineer catalytic interfaces, yet the mechanistic influence of exsolved bimetallic [...] Read more.

The electrochemical co-conversion of CO₂ and H₂O into valuable products is a promising approach toward carbon-neutral energy systems. Alloy exsolution from perovskite lattices has emerged as an effective strategy to engineer catalytic interfaces, yet the mechanistic influence of exsolved bimetallic species on CO₂/H₂O co-electrolysis remains insufficiently clarified. To address this gap, density functional theory (DFT) calculations were performed in this study to systematically examine how NiFe alloy clusters exsolved from the LSFNO (La_0.7Sr_0.3Fe_0.9Ni_0.1O_3-δ) (111) surface modify the electronic structure of the interfacial region and promote the RWGS reaction in CO₂/H₂O co-electrolysis. Our work highlights bimetallic alloy exsolution as a powerful strategy for improving co-electrolysis catalysts and offers valuable guidance for the rational design of next-generation high-entropy oxide systems. Full article

(This article belongs to the Special Issue 15th Anniversary of Catalysts: The Development and Future of Computational Catalysis)

► Show Figures

Graphical abstract

29 pages, 4285 KB

Open AccessReview

Plasma-Catalytic CO₂-to-Energy Conversion: Fundamentals, Applications, Challenges, and Perspectives

by Jingwen Huang, Junlei Wang and He Guo

Catalysts 2026, 16(6), 514; https://doi.org/10.3390/catal16060514 - 1 Jun 2026

Abstract

Efficient utilization of carbon dioxide (CO₂) is a critical route toward carbon cycling and low-carbon energy systems. Compared with conventional thermocatalysis, photocatalysis, and electrocatalysis, plasma catalysis can activate CO₂ under relatively mild conditions through high-energy electrons, vibrationally excited molecules, radicals, [...] Read more.

Efficient utilization of carbon dioxide (CO₂) is a critical route toward carbon cycling and low-carbon energy systems. Compared with conventional thermocatalysis, photocatalysis, and electrocatalysis, plasma catalysis can activate CO₂ under relatively mild conditions through high-energy electrons, vibrationally excited molecules, radicals, and other reactive species, while catalytic surfaces can redirect reaction pathways and improve selectivity. Rather than only compiling reported performances, this review critically evaluates plasma-catalytic CO₂-to-energy conversion from three perspectives: reliable mechanistic knowledge, unresolved uncertainties in plasma–catalyst synergy, and the practical credibility of reactor–catalyst combinations. The fundamentals of non-thermal plasma, CO₂ activation, key metrics, plasma–catalyst coupling, and catalyst/reactor/operation factors are first clarified. Representative advances in CO₂ splitting, CO₂ hydrogenation, dry reforming, and CO₂–H₂O co-conversion are then compared with attention to energy input, selectivity, power determination, and data comparability. Finally, the key barriers to industrial deployment are discussed, including low energy efficiency, long-term catalyst stability under plasma exposure, uncertain absorbed-power measurement, incomplete carbon/oxygen balances, scale-up of filamentary discharges, and the lack of standardized reporting protocols. This review aims to provide a critical reference for mechanism-guided catalyst design, reactor engineering, and realistic process assessment in plasma-catalytic CO₂ utilization. Full article

► Show Figures

Graphical abstract

27 pages, 20218 KB

Open AccessArticle

Solar-Assisted Iron Sludge Photo-Fenton Catalysis for Enhanced Oxidation of Dye-Loaded Beauty Salon Wastewater

by Hossam A. Nabwey and Maha A. Tony

Catalysts 2026, 16(6), 513; https://doi.org/10.3390/catal16060513 - 1 Jun 2026

Abstract

Beauty salon wastewater is an emerging commercial greywater characterized by high chemical oxygen demand (COD), intense color, and low biodegradability due to the presence of surfactants and oxidative dye precursors. This study evaluated a solar-assisted photo-Fenton process using waste-derived iron sludge as a [...] Read more.

Beauty salon wastewater is an emerging commercial greywater characterized by high chemical oxygen demand (COD), intense color, and low biodegradability due to the presence of surfactants and oxidative dye precursors. This study evaluated a solar-assisted photo-Fenton process using waste-derived iron sludge as a heterogeneous catalyst for treating real beauty salon effluent. Operational parameters, including pH, H₂O₂ concentration, iron sludge dosage, reaction time, and temperature, were optimized based on dye removal and COD reduction. Under optimal conditions (pH = 3, H₂O₂ = 400 mg L⁻¹, iron sludge = 40 mg L⁻¹), the system achieved approximately 98% dye removal and 95% COD reduction within 50 min of irradiation. Additionally, maximum performance was observed at 40 °C, while higher temperatures reduced efficiency due to non-productive H₂O₂ decomposition. Kinetic analysis was performed, and the results indicated predominant second-order behavior. Thermodynamic evaluation confirmed an endothermic process with moderate activation energy (Eₐ = 21.8 kJ mol⁻¹). Response surface methodology confirmed strong parameter interactions and high predictive accuracy. The integration of solar irradiation with iron sludge valorization provides a sustainable and decentralized solution for treating dye-loaded beauty salon wastewater. Full article

(This article belongs to the Special Issue Novel Advanced Oxidation Processes for Catalytic Degradation of Emerging Contaminants)

► Show Figures

Figure 1

12 pages, 20687 KB

Open AccessFeature PaperArticle

Ligand Engineering of Cu-Based Metal–Organic Framework for Enhanced Electrocatalytic Urea Synthesis from N₂ and CO₂

by Xinlu Xiong, Donglin Song, Qiang Ren, Xu Xiang and Jiongliang Yuan

Catalysts 2026, 16(6), 512; https://doi.org/10.3390/catal16060512 - 1 Jun 2026

Abstract

The electrocatalytic reduction in N₂ and CO₂ into urea under ambient conditions provides a promising strategy for sustainable nitrogen fixation and carbon utilization. However, the low activity and poor selectivity toward urea limit its practical application. Herein, a dual-ligand Cu-based metal–organic [...] Read more.

The electrocatalytic reduction in N₂ and CO₂ into urea under ambient conditions provides a promising strategy for sustainable nitrogen fixation and carbon utilization. However, the low activity and poor selectivity toward urea limit its practical application. Herein, a dual-ligand Cu-based metal–organic framework (Cu-BTC/NH₂BDC) was constructed via ligand engineering strategy. The introduction of 2-NH₂BDC modulated the electronic structure of Cu sites, generating electron-enriched Cu centers that facilitate CO₂ activation, while the hydrogen bonding interaction between the amino and carboxyl groups promotes the activation of N₂. As a result, the optimized Cu-BTC/NH₂BDC catalyst achieved a urea yield of 6.59 mmol g⁻¹ h⁻¹ with a Faradaic efficiency of 22.85% at −0.2 V versus reversible hydrogen electrode (vs. RHE), outperforming single-ligand counterparts. In situ Raman spectroscopy measurement revealed enhanced the formation of *CO, *NN, and C-N intermediates, indicating improved C-N coupling efficiency. This work provides a feasible strategy for regulating active sites in MOF-based catalysts toward efficient urea electrosynthesis. Full article

(This article belongs to the Special Issue Catalysts for CO₂ Conversions)

► Show Figures

Figure 1

12 pages, 2399 KB

Open AccessArticle

Lipase-Catalyzed Green Synthesis of Multisubstituted Cyanopyrazoles in an Aqueous Medium

by Fan Zhang, Xuejin Zhang, Lezhao Liu and Zhi Wang

Catalysts 2026, 16(6), 511; https://doi.org/10.3390/catal16060511 - 1 Jun 2026

Abstract

The present work establishes a sustainable and environmentally benign biocatalytic strategy for the construction of multisubstituted cyanopyrazoles via [3+2] cycloaddition, employing lipase as a highly efficient and practical catalyst. Under the optimized mild reaction conditions, this protocol enables the preparation of structurally diverse [...] Read more.

The present work establishes a sustainable and environmentally benign biocatalytic strategy for the construction of multisubstituted cyanopyrazoles via [3+2] cycloaddition, employing lipase as a highly efficient and practical catalyst. Under the optimized mild reaction conditions, this protocol enables the preparation of structurally diverse cyanopyrazole derivatives with high to excellent isolated yields. The substrate used in this method is the in situ-generated diazoacetonitrile. The corresponding conversion was carried out under mild aqueous conditions, avoiding the flammable and explosive characteristics of diazoacetonitrile. The established protocol exhibits a representative substrate scope and good functional group compatibility. Molecular docking was employed to investigate the reaction, highlighting the significant impact of the active-site architecture of the lipase on this reaction. This biocatalytic approach not only enriches the synthetic toolbox for the preparation of valuable cyanopyrazole scaffolds but also highlights the potential of lipase-catalyzed promiscuous reactions in the green synthesis of pharmaceutically relevant heterocyclic compounds. Full article

(This article belongs to the Special Issue Recent Advances in Enzyme Catalysis and Enzyme Engineering)

► Show Figures

Graphical abstract

29 pages, 8422 KB

Open AccessArticle

CuTiO₃ Perovskite-Type as an Efficient Catalyst for Alkaline Lignin Depolymerization Towards Selective Vanillin Production

by Ratheeshkumar Shanmugam, Arul Chan Basha, Vinod Kumar, Saravanan Ramiah Shanmugam, Malinee Sriariyanun and Ponnusami Venkatachalam

Catalysts 2026, 16(6), 510; https://doi.org/10.3390/catal16060510 - 1 Jun 2026

Abstract

Lignin is one of the most abundant biopolymers in nature. The major challenge in lignin depolymerization lies in the formation of complex mixtures that require extensive downstream separation. Selective depolymerization strategies aim to overcome this limitation by promoting controlled bond cleavage while suppressing [...] Read more.

Lignin is one of the most abundant biopolymers in nature. The major challenge in lignin depolymerization lies in the formation of complex mixtures that require extensive downstream separation. Selective depolymerization strategies aim to overcome this limitation by promoting controlled bond cleavage while suppressing undesired secondary reactions. In this work, a series of rare-earth-free, perovskite-type mixed metal oxides with general compositions Zn_xNi_1–xTiO₃ and Cu_yNi_1–yTiO₃ were synthesized and evaluated as heterogeneous catalysts for the base-catalyzed depolymerization of lignin. Among the investigated materials, CuTiO₃ exhibited superior catalytic performance, enabling the formation of vanillin as the dominant monomer with high selectivity. The selected catalyst was further characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) surface area analysis. The combined effects of key reaction parameters, including temperature, pressure, lignin-to-catalyst ratio, NaOH concentration, and reaction time, were systematically investigated using response surface methodology (RSM). Under the optimized conditions (154 °C, 0.3 MPa, lignin-to-catalyst ratio of 24.5:1, 10 mL of 0.5 M NaOH, and 12 h reaction time), a monomer yield of 11.5 ± 0.46% with ~81% GC-selectivity toward vanillin was achieved. These findings demonstrate that perovskite-type titanates can serve as robust and reusable catalysts. Full article

(This article belongs to the Special Issue Catalysis and New Energy Materials)

► Show Figures

Graphical abstract

17 pages, 9169 KB

Open AccessArticle

High-Efficiency Falling Thin-Film Photocatalytic Reactor for the Simultaneous and Competitive Removal of Recalcitrant Pharmaceuticals: A Case Study on Spiramycin and Naproxen

by Amel Ounnar, Hicham Zeghioud, Mohammod Hafizur Rahman, Amine Aymen Assadi, Abdelkrim Bouzaza, Lotfi Mouni and Fatiha Bentahar

Catalysts 2026, 16(6), 509; https://doi.org/10.3390/catal16060509 - 1 Jun 2026

Abstract

This study investigates the TiO₂ photocatalytic degradation of naproxen (NPX), a nonsteroidal anti-inflammatory drug, and spiramycin (SPM), a macrolide antibiotic, in aqueous solution. Experiments were conducted using a closed-loop falling thin-film photoreactor equipped with external UV lamps, with particular focus on the [...] Read more.

This study investigates the TiO₂ photocatalytic degradation of naproxen (NPX), a nonsteroidal anti-inflammatory drug, and spiramycin (SPM), a macrolide antibiotic, in aqueous solution. Experiments were conducted using a closed-loop falling thin-film photoreactor equipped with external UV lamps, with particular focus on the competitive degradation behavior when both pharmaceuticals are present simultaneously. Under optimized conditions such as natural pH, UV light intensity of 38 Wm⁻², and a recirculation flow rate of 25 L h⁻¹, the TiO₂-UV process achieved near-complete degradation of the parent compound (≥99%) for both compounds, whether treated individually or in combination. The degradation kinetics followed a pseudo-first-order model, consistent with heterogeneous photocatalytic systems at low pollutant concentrations. The apparent pseudo-first-order rate constants (k_app) were 0.025 min⁻¹ for NPX and 0.087 min⁻¹ for SPM in single-component systems. In competitive degradation, k_app ranged from 0.005 to 0.007 min⁻¹ for NPX and from 0.003 to 0.031 min⁻¹ for SPM, highlighting the influence of competitive adsorption and reactive-site interaction during simultaneous treatment. Mineralization efficiency differed between the compounds, reaching up to 67% for SPM and 41% for NPX when treated individually, suggesting the formation of more persistent by-products during naproxen degradation. Under competitive conditions, total mineralization rates ranged from 51% to 67% depending on the SPM/NPX molar ratio. Full article

(This article belongs to the Special Issue Green and Intensified Photocatalytic Reactors for Sustainable Air and Water Remediation)

► Show Figures

Graphical abstract

17 pages, 9059 KB

Open AccessArticle

NiFe Bimetallic Doped Geopolymer Catalyst for Hydrogen Evolution and Overall Water Splitting

by Jian Gong, Qian Dong, Xiaomei Peng, Yan He, Xuemin Cui and Leping Liu

Catalysts 2026, 16(6), 508; https://doi.org/10.3390/catal16060508 - 1 Jun 2026

Abstract

Achieving efficient overall water splitting with non-precious metal catalysts remains a significant challenge due to the sluggish kinetics of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, we report a nickel–iron bimetallic doped geopolymer electrocatalyst (Ni_0.9Fe [...] Read more.

Achieving efficient overall water splitting with non-precious metal catalysts remains a significant challenge due to the sluggish kinetics of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, we report a nickel–iron bimetallic doped geopolymer electrocatalyst (Ni_0.9Fe_0.1-GP) fabricated via a one-step alkali activation method on 316L stainless steel. Structural characterizations reveal that Fe³⁺ incorporation alters the distribution of Na⁺ and Ni²⁺ within the geopolymer network and modulates the Ni electronic structure. Electrochemical measurements show that Ni_0.9Fe_0.1-GP delivers an HER overpotential of 332.42 mV and an OER overpotential of 227.31 mV at 10 mA cm⁻², outperforming Ni-GP and bare 316L SS. The practical operating voltage of Ni_0.9Fe_0.1-GP is 1.81 V, while the two-electrode electrolyzer delivers a comparable current density at 1.90 V (after accounting for uncompensated system resistances). Long-term stability tests demonstrate the superior durability of Ni_0.9Fe_0.1-GP during HER, OER, and overall water splitting. Mechanistic studies reveal the dual role of Fe³⁺: substantially increasing the electrochemical active surface area (ECSA) while modulating the Ni electronic structure, and improving structural stability through strong chemical anchoring within the geopolymer network. This work provides new insights into cost-effective bifunctional electrocatalysts and expands the application of geopolymers as functional catalytic supports for water splitting. Full article

(This article belongs to the Special Issue 15th Anniversary of Catalysts—Industrial Development of Catalytic Materials for the Energetic Transition)

► Show Figures

Graphical abstract

19 pages, 3265 KB

Open AccessArticle

A Ternary Ag Species and Zr-Doped TiO₂ Photocatalyst for Enhanced MB Decolorization Under Low-Intensity Visible LEDs

by Pichai Soison, Chamorn Chawengkijwanich, Hugo de Lasa and Siriluk Chiarakorn

Catalysts 2026, 16(6), 507; https://doi.org/10.3390/catal16060507 - 1 Jun 2026

Abstract

This study explored the influence of high silver (Ag) loading (5–10 mol%) on the photocatalytic performance of zirconium (Zr) co-doped TiO₂ (AZT) with a low Zr content. Although various Ag/Zr ratios have been reported, the effect of high Ag loading combined with [...] Read more.

This study explored the influence of high silver (Ag) loading (5–10 mol%) on the photocatalytic performance of zirconium (Zr) co-doped TiO₂ (AZT) with a low Zr content. Although various Ag/Zr ratios have been reported, the effect of high Ag loading combined with low Zr content remains largely unrevealed, particularly in low-temperature synthesis where the role of Zr as a phase inhibitor is less critical. To address this gap, the AZT photocatalyst was fabricated via a solvothermal method combined with organic-free peroxy route. Characterization indicated Zr⁴⁺ incorporated into the TiO₂ lattice, inducing structural distortions and promoting Ti³⁺ defect states. Simultaneously, silver existed as ternary Ag species, which functioned as visible light responsive co-catalysts that enhanced light absorption via Surface Plasmon Resonance (SPR) and facilitated efficient charge separation. Photocatalytic performance was evaluated through Methylene Blue (MB) decolorization under household LED lamp. The optimized 7% Ag loaded catalyst achieved 99.4% removal efficiency within 6 h, with a reaction rate ten times higher than the Zr-doped sample. This superior activity was attributed to a p-n heterojunction and the SPR effect, narrowing the optical band gap to 2.60 eV. Radical scavenger experiments confirmed that the process was primarily driven by photogenerated holes. Full article

(This article belongs to the Special Issue 15th Anniversary of Catalysts: Recent Advances in Catalytic Reaction Engineering)

► Show Figures

Figure 1

15 pages, 2995 KB

Open AccessArticle

Comparative Analysis of Ignition and Combustion Characteristics in Straight-Channel and U-Bend Micro Catalytic Combustors: Numerical Investigation of Inlet Velocity Effects

by Zhen Wang, Jiangtao Bi, Zunmin Li, Mengmeng Yu, Wenli Ma, Wei Zhai, Jinsheng Lv and Xiangjin Kong

Catalysts 2026, 16(6), 506; https://doi.org/10.3390/catal16060506 - 1 Jun 2026

Abstract

This paper presents a numerical comparative study on the ignition characteristics of straight-channel and U-bend micro catalytic combustors, with particular focus on the role of inlet velocity. A two-dimensional computational fluid dynamics model with coupled gas-phase and surface catalytic reaction kinetics for propane [...] Read more.

This paper presents a numerical comparative study on the ignition characteristics of straight-channel and U-bend micro catalytic combustors, with particular focus on the role of inlet velocity. A two-dimensional computational fluid dynamics model with coupled gas-phase and surface catalytic reaction kinetics for propane combustion is developed using a fluid simulation program ANSYS Fluent. The catalyst coating (Pt/Al₂O₃) is modeled as a zero-thickness reaction surface, and the U-bend design features an uncoated recirculating channel to ensure identical catalyst loading between the two configurations. Simulations are conducted over an inlet velocity range of 0.25–8 m/s. Key ignition and combustion metrics including ignition temperature, ignition time, maximum combustion temperature, heterogeneous reaction contribution, and thermal/species field distributions are systematically compared. Results reveal a crossover in relative performance depending on flow regime. At low velocities (≤2 m/s), the straight-channel combustor exhibits lower ignition temperatures; at high velocities (≥4 m/s), the U-bend design achieves superior ignition performance with lower ignition temperatures (e.g., 526 K vs. 555 K at 8 m/s) and higher combustion temperatures (1726 K vs. 1474 K at 8 m/s). However, the straight-channel combustor consistently yields shorter ignition times across all velocities (25.9–108.6 s) compared to the U-bend (52.6–145.2 s). The heterogeneous reaction contribution decreases with increasing inlet velocity for both designs, with the straight-channel maintaining higher values than the U-bend. The U-bend achieves higher maximum temperatures due to enhanced heat recirculation, particularly at high flow rates. The findings suggest that the U-bend configuration is advantageous for high-flow-rate applications requiring low ignition temperatures and high combustion temperatures, whereas the straight-channel design is preferable for rapid cold-start scenarios. Full article

► Show Figures

Figure 1

19 pages, 8232 KB

Open AccessArticle

Binder-Free Co₃O₄ Nanoneedles on Nickel Foam for Selective Electrocatalytic Nitrate Reduction to Ammonium

by Ruoxi Wu, Yangwei Luo, Jiahong Yang and Peng Xu

Catalysts 2026, 16(6), 505; https://doi.org/10.3390/catal16060505 - 1 Jun 2026

Abstract

A binder-free Co₃O₄ nanoneedle electrode grown directly on nickel foam (Co₃O₄@NF) was fabricated by hydrothermal synthesis followed by calcination and evaluated for electrocatalytic nitrate reduction to ammonium. The integrated three-dimensional architecture combines the catalytic activity of [...] Read more.

A binder-free Co₃O₄ nanoneedle electrode grown directly on nickel foam (Co₃O₄@NF) was fabricated by hydrothermal synthesis followed by calcination and evaluated for electrocatalytic nitrate reduction to ammonium. The integrated three-dimensional architecture combines the catalytic activity of Co₃O₄ with the high conductivity and open porosity of nickel foam, thus exposing abundant active sites, shortening electron-transfer pathways, and facilitating mass transport. Among the electrodes prepared at different calcination temperatures, Co₃O₄@NF calcined at 400 °C delivered the best performance. Under the optimal conditions of −1.4 V vs. Ag/AgCl, pH 7, and an initial NO₃⁻-N concentration of 50 mg L⁻¹, the electrode achieved 83.4% nitrate removal within 480 min together with 98.7% ammonium selectivity. Electrochemical measurements revealed a markedly enlarged electrochemically active surface area and reduced charge-transfer resistance after Co₃O₄ loading. Mechanistic analyses via TBA quenching experiments and DFT calculations revealed that both the direct pathway and the hydrogen-assisted indirect pathway were operative, with the indirect pathway being dominant due to its lower free energy barrier while maintaining negligible nitrite accumulation. The electrode also showed good cycling stability and retained high ammonium selectivity in real water matrices. These results demonstrate that binder-free Co₃O₄ nanoneedles supported on nickel foam constitute a promising cathode architecture for coupling nitrate removal with ammonia recovery. Full article

► Show Figures

Figure 1

Journal Description

Catalysts

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI