Catalysts

14 pages, 3594 KB

Open AccessFeature PaperArticle

ZnAl-Hydrotalcite-Catalyzed Aqueous-Phase Rearrangement of Furfuryl Alcohol to 4-Hydroxycyclopent-2-Enone

by Yue Zhao, Ling An, Hui Zhang, Tong Zhang, Xing Zhang, Li Huang, Song Jin, Wei Wang and Ning Li

Catalysts 2026, 16(7), 634; https://doi.org/10.3390/catal16070634 - 13 Jul 2026

Abstract

4-Hydroxycyclopent-2-enone (HCP), a chemical substance with a unique molecular structure and distinct physical properties, is an important intermediate for the synthesis of natural products, chemicals, and liquid fuels, demonstrating exceptionally high application value. This study introduces a novel approach for HCP synthesis via [...] Read more.

4-Hydroxycyclopent-2-enone (HCP), a chemical substance with a unique molecular structure and distinct physical properties, is an important intermediate for the synthesis of natural products, chemicals, and liquid fuels, demonstrating exceptionally high application value. This study introduces a novel approach for HCP synthesis via the rearrangement of furfuryl alcohol (FAL). A series of ZnAl-based hydrotalcite (HT) catalysts was prepared and characterized by SEM, XPS, XRD, NH₃-TPD, and CO₂-TPD. HCP is efficiently synthesized by the rearrangement of furfuryl alcohol in water at a relatively low temperature of 205 °C. Using a 10 wt.% aqueous solution of furfuryl alcohol as the raw material, the yield of HCP remained stable at 80.2% under the selected reaction conditions (ZnAl-HT-1: 1–500 °C as catalyst, 205 °C, and 5 min). It is worth noting that when the concentration of furfuryl alcohol solution was reduced to 5%, the conversion of furfuryl alcohol reached 100%, and the HCP yield reached an excellent 92.5%. The exceptional performance observed can be primarily attributed to several key factors associated with the ZnAl-HT-1: 1–500 °C catalyst: its expansive specific surface area and ample pore volume, the distinctive layered structure inherent to hydrotalcites, and its well-balanced acid–base properties, featuring optimal densities of acid and base sites with a uniform distribution of acidic and basic active centers that cooperate synergistically to promote the reaction. Full article

(This article belongs to the Special Issue Advances in Catalysis Science and Technology for Sustainable Development)

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24 pages, 6800 KB

Open AccessReview

Spin-Regulated Oxygen Reduction Electrocatalysis: Recent Progress and Future Perspectives

by Lin Ju, Xiao Tang, Xinqi Ren, Xueying Gao and Kun Wang

Catalysts 2026, 16(7), 633; https://doi.org/10.3390/catal16070633 - 13 Jul 2026

Abstract

The oxygen reduction reaction (ORR) is the cathode cornerstone of fuel cells and metal-air batteries. Its inherent spin mismatch between triplet O₂ and singlet products causes sluggish kinetics that conventional catalyst designs cannot fully overcome. This review critically summarizes the past three [...] Read more.

The oxygen reduction reaction (ORR) is the cathode cornerstone of fuel cells and metal-air batteries. Its inherent spin mismatch between triplet O₂ and singlet products causes sluggish kinetics that conventional catalyst designs cannot fully overcome. This review critically summarizes the past three years’ breakthroughs in spin-regulated ORR electrocatalysis and offers a fresh perspective beyond traditional electronic and geometric optimization. We first dissect the physical mechanism of spin-selective electron transfer required for the 4e⁻ pathway. We then systematically present four strategies for modulating the spin state of transition-metal active sites, namely strain engineering, defect engineering, heteroatom doping, and interfacial heterostructures. Subsequently, we highlight the emerging chirality-induced spin selectivity effect, where chiral organic molecules or intrinsically chiral inorganic materials act as spin filters without an external magnetic field, enabling spin-matched electron transfer and enhanced ORR performance. At the end of our review, we identify several key challenges, including the lack of in situ techniques to dynamically track spin states under operating conditions, the limited stability and universality of chiral catalysts, and the insufficient understanding of synergistic effects between spin control and traditional design parameters. We also outline future research directions, such as developing operando spin characterization, constructing robust chiral inorganic nanostructures, and employing high-throughput computational screening to integrate spin, geometric, and electronic level design. Our review provides a timely and comprehensive framework that bridges spin physics with electrocatalyst design, offering critical mechanistic insights and practical guidelines. Full article

(This article belongs to the Special Issue Catalysis for a Sustainable Future: Powering New Energy and Protecting the Environment)

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22 pages, 4929 KB

Open AccessArticle

Morphological Impact of Iron Tungstate on Electrochemical Properties in the Oxygen Evolution Reaction

by Andarair Gomes dos Santos, Yassine Elaadssi, Virginie Chevallier, Christine Leroux and Madjid Arab

Catalysts 2026, 16(7), 632; https://doi.org/10.3390/catal16070632 - 13 Jul 2026

Abstract

In this study, the influence of nanostructure and morphology was used as a comparative strategy to investigate the material’s performance. For this purpose, two distinct morphologies, one of which is novel for iron tungstate (nanoplatelets) and obtained by the hydrothermal method, were tested [...] Read more.

In this study, the influence of nanostructure and morphology was used as a comparative strategy to investigate the material’s performance. For this purpose, two distinct morphologies, one of which is novel for iron tungstate (nanoplatelets) and obtained by the hydrothermal method, were tested to verify their influence on the catalytic activity, reaction kinetics, and operational stability of the oxygen evolution reaction. Although the self-organized rosette and nanoplatelet morphologies maintain a monoclinic ferberite-type structure, the 2D nanoplatelet architecture shows an almost 30% reduction in catalytic activity and a 16% increase in reaction rate in basic medium (1 M KOH), in addition to four times higher turnover frequencies (TOF). Furthermore, the new morphology (nanoplatelets) provides higher charge density, lower charge transfer resistance, and favorable band edge positions, resulting in greater oxidation capacity (10 times more). Regarding the stability factor, both morphologies show a slight degradation over 1000 cycles, but the nanoplatelet morphology maintains almost constant activity, while the self-organized rosette morphology shows a performance drop of approximately 25%. These results demonstrate that morphological engineering is an effective means of improving electrocatalytic performance. Full article

(This article belongs to the Special Issue Catalytic Conversion of Small Molecules for Energy and Environmental Sustainability)

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16 pages, 2063 KB

Open AccessArticle

Mixed N₃S₂-Ligated Nonheme Fe(IV)=O Species Balancing Stability and Oxidation Reactivity as a Platform for Nonheme Iron Oxidation Catalysis

by Hanaa Mansour, Ahmed M. Albasiony, Safaa N. Abdou, Mohamed M. Ibrahim, Rudi van Eldik and Shaban Y. Shaban

Catalysts 2026, 16(7), 631; https://doi.org/10.3390/catal16070631 - 13 Jul 2026

Abstract

Mononuclear nonheme iron(IV)–oxo species supported by mixed nitrogen–sulfur (N/S) ligands remain scarce, despite the prevalence of sulfur donors in biological iron sites and their expected impact on ferryl reactivity and catalyst design. In this work, a seven-coordinate iron(II) complex, [(N₃S₂ [...] Read more.

Mononuclear nonheme iron(IV)–oxo species supported by mixed nitrogen–sulfur (N/S) ligands remain scarce, despite the prevalence of sulfur donors in biological iron sites and their expected impact on ferryl reactivity and catalyst design. In this work, a seven-coordinate iron(II) complex, [(N₃S₂)Fe^II(ClO₄)₂], bearing a rigid 15-membered N₃S₂ macrocycle, is shown to rapidly generate a mononuclear nonheme Fe^IV=O intermediate upon reaction with m-chloroperbenzoic (m-CPBA) acid in acetonitrile. The Fe^IV=O species forms within ≤2 s and is thermally persistent (t₁/₂ = 4.3 h at 25 °C), albeit in partial yield (~39% Fe^IV=O by Mössbauer spectroscopy), placing it in an intermediate regime between highly reactive but short-lived ferryl species and more inert, long-lived analogues. The intermediate is characterized by Mössbauer spectroscopy (δ = 0.35 mm s⁻¹, ΔE_Q = 0.90 mm s⁻¹, Γ_FWHM = 0.30 mm s⁻¹, relative area = 39.4%), EPR silence, a UV–vis absorption band at 428 nm, and cryogenic high-resolution ESI–MS (m/z 223.510, (N₃S₂)Fe^IV=O²⁺). Stopped-flow kinetic studies reveal saturation behavior that is well described by a pre-equilibrium oxidant-association model and subsequent O–O bond activation, with apparent activation parameters of ΔH^‡ = 17.7 kJ mol⁻¹ and ΔS^‡ = −155 J mol⁻¹ K⁻¹, indicating a highly ordered transition state within the seven-coordinate N₃S₂ framework under the conditions employed. Functionally, the Fe^IV=O species mediates clean oxygen-atom transfer to triphenylphosphine (k₂ = 8.1 × 10⁻² M⁻¹ s⁻¹) with an effective turnover number of ~12 after correction for the Fe^IV=O yield, establishing that this mixed N/S platform is catalytically competent under mild conditions, though less reactive than state-of-the-art all-nitrogen systems. Collectively, these findings identify the seven-coordinate N₃S₂ macrocycle as a mixed-donor platform that moderately extends ferryl lifetime while retaining measurable oxo-transfer reactivity, providing mechanistic guidance for the development of nonheme iron oxidation catalysts that incorporate sulfur donors. Full article

(This article belongs to the Special Issue Emerging Topics in Catalytic Reactions: From Catalyst Preparation to Application in Diverse Fields)

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16 pages, 6922 KB

Open AccessArticle

The Removal of Single and Binary Components of Hydrogen Sulfide and Dimethyl Disulfide in a Post-Plasma Catalysis Reactor: The Correlation of the Ozone Demand Factor with Specific Input Energy

by Jian Zhang, Xueyu Hu, Min Zhan, Weiqiang Zhu and Chao Long

Catalysts 2026, 16(7), 630; https://doi.org/10.3390/catal16070630 - 13 Jul 2026

Abstract

Odorous gases such as hydrogen sulfide (H₂S) and dimethyl disulfide (DMDS) pose significant risks to human health and environmental quality. Non-thermal plasma (NTP) technology offers an effective alternative for odor treatment, but challenges remain regarding byproduct formation (e.g., ozone) and energy [...] Read more.

Odorous gases such as hydrogen sulfide (H₂S) and dimethyl disulfide (DMDS) pose significant risks to human health and environmental quality. Non-thermal plasma (NTP) technology offers an effective alternative for odor treatment, but challenges remain regarding byproduct formation (e.g., ozone) and energy efficiency. In this study, a post-plasma catalysis (PPC) system combining a wire cylinder pulsed corona discharge reactor with a CuO/MnO₂-C ozone decomposition catalyst was employed to remove single and binary components of H₂S and DMDS. The effects of specific input energy (SIE), inlet concentration (C_in), and catalyst on removal efficiency, energy yield, and ozone emission were systematically investigated. A novel parameter, the ozone demand factor (Df), was defined to quantify the relationship between ozone consumption and pollutant removal. The results show that for single-component removal, regulating SIE/Cin within specific ranges (0.22–0.25 for H₂S and ~0.72 for DMDS) enables simultaneous low outlet concentrations of both pollutants and ozone. For binary H₂S-DMDS mixtures, ln(Df) exhibits a strong linear positive correlation with SIE/Σ(C_in) (R² = 0.968), and controlling SIE/Σ(C_in) at 0.28 yields ln(Df) ≈ 4, ensuring outlet H₂S < 5.0 ppm, DMDS < 3.0 ppm, and ozone < 5.0 ppm. This study demonstrates that the ozone demand factor serves as a critical control parameter for optimizing PPC systems, providing a practical tool for balancing pollutant removal and ozone emission in industrial odor treatment applications. Full article

(This article belongs to the Section Catalytic Materials)

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19 pages, 12767 KB

Open AccessArticle

Pd(WC_1−x)/TEG Electrodes Prepared by Chemical Deposition of Palladium onto CVD-Produced Tungsten Carbide Layers as Promising Catalysts for Hydrogen Evolution and Formic Acid Oxidation Reactions

by Denis I. Cherkasov, Vitaly V. Kuznetsov, Artem A. Zhbanov, Vladimir V. Zhulikov, Evgeny A. Ruban, Elena A. Filatova, Veniamin S. Boldyrev, Tatiana D. Khromova and Konstantin E. German

Catalysts 2026, 16(7), 629; https://doi.org/10.3390/catal16070629 - 12 Jul 2026

Abstract

Non-stoichiometric tungsten carbide WC_1−x layers (~20 mm thickness) were used as a reductant substrate to deposit palladium nanoparticles under open-circuit conditions in aqueous solutions. The prepared Pd(WC_1−x)/TEG electrodes (TEG—thermally expanded graphite) were studied by a complex of modern [...] Read more.

Non-stoichiometric tungsten carbide WC_1−x layers (~20 mm thickness) were used as a reductant substrate to deposit palladium nanoparticles under open-circuit conditions in aqueous solutions. The prepared Pd(WC_1−x)/TEG electrodes (TEG—thermally expanded graphite) were studied by a complex of modern physical methods: scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman Spectroscopy. The reduction of Pd(II) species to the metallic state was confirmed by XPS and XRD. The coherent scattering domain (CSD) for Pd particles was determined using the Scherrer formula (peak broadening analysis) with the LaBeil profile fitting the XRD pattern. It was ca. 16 nm, which would correspond to a specific surface area of palladium of 30.9 m²·g⁻¹, assuming a spherical shape of its particles. According to electrochemical studies, the specific area of palladium is significantly lower (8.5 m²·g⁻¹ in 0.1 M PdCl₂ after 2 h of deposition), which is due to the inevitable coalescence of metal nanoparticles during the currentless deposition process. Pd(WC_1−x) composites demonstrated high catalytic activity in the hydrogen evolution reaction (HER) and formic acid oxidation reaction (FAOR). Thus, currentless deposition can be considered as a relatively simple method for producing electrode catalysts. Full article

(This article belongs to the Special Issue The Applications of Heterogeneous Catalysis in Energy Utilization)

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22 pages, 2182 KB

Open AccessFeature PaperArticle

Phosphate Modification Promotes Low-Temperature NH₃-SCO over Cu/CeO₂ Through Coupled Regulation of Surface Acidity and Oxygen Species

by Shiqi Ma, Haoyang Li, Yuchen Huang, Kai Sun, Yuejia Huang, Yarong Fang and Yan Du

Catalysts 2026, 16(7), 628; https://doi.org/10.3390/catal16070628 - 11 Jul 2026

Abstract

Selective catalytic oxidation of ammonia (NH₃-SCO) is a promising technology for ammonia abatement. Cu/CeO₂ catalysts have attracted extensive attention because of their strong metal–support interaction and favorable redox properties. However, their practical application is still limited by insufficient low-temperature catalytic [...] Read more.

Selective catalytic oxidation of ammonia (NH₃-SCO) is a promising technology for ammonia abatement. Cu/CeO₂ catalysts have attracted extensive attention because of their strong metal–support interaction and favorable redox properties. However, their practical application is still limited by insufficient low-temperature catalytic activity and unsatisfactory control of by-product formation. Herein, phosphate-functionalized Cu/CeO₂ catalysts were fabricated to regulate surface acidity and oxygen species behavior, thereby promoting low-temperature NH₃-SCO activity. The optimal Acid-Cu/CeO₂ catalyst achieved 90% NH₃ conversion at 260 °C, corresponding to a 192 °C decrease in T₉₀ compared with pristine Cu/CeO₂ (452 °C). Kinetic analysis showed that the apparent activation energy decreased from 125.78 to 84.70 kJ mol⁻¹ after phosphoric acid modification. In addition, Acid-Cu/CeO₂ maintained relatively high N₂ selectivity and lower NO_x selectivity over the tested temperature range, indicating that phosphate modification suppresses the deep oxidation of NH₃ to NO_x by-products. Structural and surface characterization results demonstrated that Cu species remained highly dispersed on CeO₂ after modification, while surface phosphate species modified the local electronic environment and redistributed oxygen species. O 1s XPS and O₂-TPD results revealed that phosphate modification decreased the static surface adsorbed/defect-related oxygen fraction but improved the accessibility and mobility of labile surface/subsurface or weakly bound lattice oxygen species. Py-IR and DRIFTS results further showed that phosphate modification increased Brønsted/Lewis acidity, enhanced NH₃ adsorption and N-H activation, and facilitated the formation and subsequent consumption of NH_x/-NHO-related intermediates under reaction conditions. This work provides insights into phosphate-mediated regulation of surface acidity and oxygen mobility and offers a strategy for designing efficient low-temperature Cu/CeO₂-based NH₃-SCO catalysts. Full article

(This article belongs to the Special Issue Green Catalytic Materials for Environmental Application)

15 pages, 16809 KB

Open AccessFeature PaperArticle

CO₂ Methanation over Supported Nickel Catalysts Produced via Spray Pyrolysis: Investigation of Support Effects on Activation, Activity, and Stability

by Gerrit Küchen, Vinzent Olszok, Alfred P. Weber and Thomas Turek

Catalysts 2026, 16(7), 627; https://doi.org/10.3390/catal16070627 - 10 Jul 2026

Abstract

The activity and stability of Ni-based catalysts for CO₂ methanation strongly depend on the morphology and chemical composition of the support. In this work, Ni catalysts with four oxidic supports (SiO₂, Al₂O₃, CeO₂, ZrO [...] Read more.

The activity and stability of Ni-based catalysts for CO₂ methanation strongly depend on the morphology and chemical composition of the support. In this work, Ni catalysts with four oxidic supports (SiO₂, Al₂O₃, CeO₂, ZrO₂) were synthesized via a one-step spray pyrolysis approach. Comprehensive characterization by STEM-EDS, XRD, and N₂ adsorption was used to resolve support morphology, Ni particle size, and nanoparticle incorporation into the support matrix. Beyond steady-state activity and reaction mechanism, the support material also affects the activation period and initial stability of the catalysts. By combining temperature-programmed methanation scans on fresh and spent samples with long-term stability tests, we clearly identify support-dependent changes in initial activity and their correlation with Ni–support interactions. Enhanced physical embedding and stronger chemical binding of Ni nanoparticles significantly reduce activity changes during the first hours on stream. Overall, this study demonstrates that the support and the corresponding metal–support interactions not only affect reaction pathways and activity, but also the pretreatment and activation required to reach a stable operating point, which is of crucial importance in kinetic catalysis research. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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21 pages, 20615 KB

Open AccessArticle

Synergistic Combination of Triazole and BDC-MOF with TM-LDH in a One Pot for Improved Electrocatalytic Urea Oxidation

by Doaa Essam, Abdullah S. Alawam, Ahmed A. Allam, Haifa E. Alfassam, Shima Gamil and Rehab Mahmoud

Catalysts 2026, 16(7), 626; https://doi.org/10.3390/catal16070626 - 10 Jul 2026

Abstract

The development of highly efficient and low-cost electrocatalysts for the urea oxidation reaction (UOR) is crucial for advancing urea fuel cell technologies. In this work, MgZnFe-layered double hydroxide (LDH), LDH/BDC-MOF, and LDH/1,2,4-triazole (LDH/TZ) nanocomposites were successfully synthesized via a simple one-pot co-precipitation method. [...] Read more.

The development of highly efficient and low-cost electrocatalysts for the urea oxidation reaction (UOR) is crucial for advancing urea fuel cell technologies. In this work, MgZnFe-layered double hydroxide (LDH), LDH/BDC-MOF, and LDH/1,2,4-triazole (LDH/TZ) nanocomposites were successfully synthesized via a simple one-pot co-precipitation method. The structural, morphological, textural, and thermal properties of the prepared materials were investigated using XRD, FTIR, SEM, EDX, BET, and TGA analyses. SEM observations revealed that pristine LDH consisted of stacked thin nanosheets with significant layer aggregation, whereas LDH/BDC-MOF exhibited MOF-pillared structures and LDH/TZ formed a highly porous interconnected three-dimensional network that effectively suppressed nanosheet restacking. BET analysis showed a remarkable enlargement in pore size from 6.7 nm for LDH to 34.5 nm for LDH/TZ. The electrocatalytic performance toward UOR was evaluated by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy in 1.0 M KOH, containing different urea concentrations. Among all investigated electrodes, LDH/TZ exhibited the highest catalytic activity, delivering anodic current densities of 106, 132, 166, 180, and 202 mA cm⁻² at urea concentrations of 0.2, 0.4, 0.6, 0.8, and 1.0 M, respectively. Furthermore, LDH/TZ displayed a lower onset potential of 0.41 V compared with 0.49 V for LDH/BDC-MOF and 0.56 V for pristine LDH. The enhanced activity was further supported by a high double-layer capacitance of 9.7 μF cm⁻², a large electrochemically active surface area of 0.24 cm², and a low charge-transfer resistance of 2.9 Ω. Chronoamperometric measurements demonstrated excellent durability with a stable current density of approximately 73 mA cm⁻² after 3600 s, while cyclic stability reached 94% after 100 cycles. The superior performance of LDH/TZ is attributed to the synergistic effect of the nitrogen-rich triazole ligand, enlarged pore structure, enhanced active-site exposure, and accelerated charge-transfer kinetics, highlighting its strong potential as an efficient electrocatalyst for direct urea fuel cell applications. Full article

(This article belongs to the Special Issue Young Researchers in Electrocatalysis)

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22 pages, 23593 KB

Open AccessArticle

Research and Validation of the Photogenerated Carrier Transfer Mechanism in CdS/TiO₂ Systems Relative to the p–n Junction Theory

by Nannan Yuan, Sujuan Zhang and Gaoli Chen

Catalysts 2026, 16(7), 625; https://doi.org/10.3390/catal16070625 - 9 Jul 2026

Abstract

It is known that when an n-type semiconductor and a p-type semiconductor (i.e., a p–n junction) are connected, an intrinsic electric field is formed due to the diffusion motion of majority carriers. The direction of this intrinsic electric field in the p–n junction [...] Read more.

It is known that when an n-type semiconductor and a p-type semiconductor (i.e., a p–n junction) are connected, an intrinsic electric field is formed due to the diffusion motion of majority carriers. The direction of this intrinsic electric field in the p–n junction runs from the n-type to the p-type semiconductor (n→p). If the migration directions of photogenerated charge carriers in the conduction band (CB) and valence band (VB) of the two contacting semiconductors align with the direction of the intrinsic electric field in the heterojunction, band-to-band transfer occurs. In experiments using TiO₂-based composite photocatalysts, the heterojunction catalyst forms a structure analogous to a p–n junction relative to CdS/TiO₂; however, due to differing carrier concentrations, TiO₂ exhibits a p-type character while CdS shows an n-type character. Under the influence of the intrinsic electric field, photogenerated electrons migrate to the p-type TiO₂ surface, while holes migrate to the n-type CdS surface. The migration directions of photogenerated electrons and holes in the CB and VB of both CdS and TiO₂ match those observed in a typical p–n junction, confirming that the photocarrier migration mechanism in TiO₂-dominated CdS/TiO₂ systems follows a band-to-band transfer mechanism. When CdS serves as the dominant component, rapid recombination occurs between electrons in TiO₂’s CB and holes in CdS’s VB, resulting in significant electron accumulation in TiO₂’s CB and substantial hole generation in CdS’s VB. Electrons in the CB of TiO₂, which carries a higher negative potential, reduce O₂ to •O₂⁻, while holes in the VB of CdS, possessing a higher positive potential, generate •OH⁻, thereby enhancing photocatalytic activity; thus, the photoexcited carrier transfer mechanism follows Scheme Z. Full article

(This article belongs to the Special Issue Catalysis for Sustainable Environmental Solutions)

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14 pages, 5764 KB

Open AccessArticle

Numerical Study on Ignition and Combustion Characteristics of Symmetric and Asymmetric U-Bend Catalytic Micro-Burners: A Comparison with the Straight-Channel Design

by Mengmeng Yu, Jiangtao Bi, Zunmin Li, Qingyun Sun, Guofang Feng, Wei Zhai, Xiangjin Kong and Jinsheng Lv

Catalysts 2026, 16(7), 624; https://doi.org/10.3390/catal16070624 - 9 Jul 2026

Abstract

Geometric asymmetry in recirculating micro-burners remains underexplored in catalytic micro-combustion research, despite its potential to significantly influence ignition behavior. This numerical study investigates the ignition and combustion characteristics of four micro-channel catalytic burners with distinct geometric configurations, aiming to evaluate the role of [...] Read more.

Geometric asymmetry in recirculating micro-burners remains underexplored in catalytic micro-combustion research, despite its potential to significantly influence ignition behavior. This numerical study investigates the ignition and combustion characteristics of four micro-channel catalytic burners with distinct geometric configurations, aiming to evaluate the role of asymmetry on combustion behavior. Burner 1 is a straight-channel design without heat recirculation. Burners 2–4 are U-bend recirculating configurations: Burner 2 with symmetric channel sizes, Burner 3 with a wider inlet channel, and Burner 4 with a narrower inlet channel. A two-dimensional computational fluid dynamics model with a one-step global propane oxidation mechanism and catalytic wall reactions is employed. The results show that Burner 1 exhibits the highest ignition temperature (555 K) and shortest ignition delay (28.5 s) due to its low thermal mass. Among U-bend burners, Burner 4 achieves the lowest ignition temperature (530 K) and the highest steady-state combustion temperature (1726 K), owing to reduced recirculation velocity and enhanced thermal feedback. Burner 2 shows moderate performance, while Burner 3 gives the weakest combustion intensity among recirculating designs. The heterogeneous reaction contribution is highest in Burner 1 (69.3%) and lowest in Burners 2 and 3 (~55%). Asymmetric channel sizing, particularly a narrow catalytic channel combined with a wide recirculation channel (Burner 4), significantly improves ignition and combustion performance under cold-start conditions. Full article

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23 pages, 2256 KB

Open AccessArticle

Pd/Activated Biocarbon Applied to a Glycerol Acid-Alkaline Electroreformer for Simultaneous H₂ and Electricity Production

by Fernando M. de A. Lino, Rossano Gambetta, Simone Palma Favaro and José J. Linares

Catalysts 2026, 16(7), 623; https://doi.org/10.3390/catal16070623 - 9 Jul 2026

Abstract

This manuscript proposes to valorize the macauba endocarp (E) wastes from the macauba processing by a pyrolytic + hydrothermal process to produce activated carbon (ACE), followed by chemical treatment with H₂O₂ (ACEA) and HNO₃ (ACEB). Elemental analysis, surface area, [...] Read more.

This manuscript proposes to valorize the macauba endocarp (E) wastes from the macauba processing by a pyrolytic + hydrothermal process to produce activated carbon (ACE), followed by chemical treatment with H₂O₂ (ACEA) and HNO₃ (ACEB). Elemental analysis, surface area, pore-size distribution, and surface functional groups are investigated for the different prepared materials. ACEA and ACEB offer a higher surface area and functionality than Vulcan XC-72R (VC), making them suitable as carbon supports for Pd nanoparticles. The prepared Pd/ACEA and Pd/ACEB are physicochemically characterized by X-ray diffraction and Transmission Electron Microscopy. Their electrochemical performance is initially evaluated in a 3-electrode glass cell and is found to surpass that of Pd/VC in glycerol electro-oxidation. This trend is confirmed in the glycerol acid-alkaline electroreformer, where hydrogen and electricity were simultaneously produced, achieving a maximum power density of 0.28 kW m⁻² and H₂ flux of 0.6 STP m³ m⁻² h⁻¹ at 80 °C. Full article

(This article belongs to the Special Issue 15th Anniversary of Catalysts: Feature Papers in Electrocatalysis)

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13 pages, 2791 KB

Open AccessArticle

First-Principles Insights into I Doping Effects on the Electronic Structure, Optical Properties, and CO₂ Photoreduction Performance of Bi₄O₅Br₂

by Juan Guo, Shuaishuai Liu, Chenxi Wang, Haocheng Wang and Gaihui Liu

Catalysts 2026, 16(7), 622; https://doi.org/10.3390/catal16070622 - 9 Jul 2026

Abstract

To address the insufficient visible-light absorption of Bi₄O₅Br₂ photocatalysts, first-principles density functional theory (DFT) calculations were employed to systematically investigate the effects of I doping at different concentrations (12.5%, 25%, 50%, 75%, 87.5%, and 100%) on the geometric [...] Read more.

To address the insufficient visible-light absorption of Bi₄O₅Br₂ photocatalysts, first-principles density functional theory (DFT) calculations were employed to systematically investigate the effects of I doping at different concentrations (12.5%, 25%, 50%, 75%, 87.5%, and 100%) on the geometric structure, electronic structure, optical properties, and photocatalytic CO₂ reduction performance of Bi₄O₅Br₂. Formation energy calculations and Ab initio molecular dynamics (AIMD) simulations indicate that the I-doped systems possess good thermodynamic and kinetic stability. Geometric analysis shows that I doping leads to a gradual expansion of lattice parameters along the c-axis (from 14.80 Å to 15.16 Å), due to the larger ionic radius of I⁻ compared to Br⁻. Electronic structure results reveal that all doped systems remain indirect band gap semiconductors, with the band gap decreasing from 2.56 eV for the pristine system to 2.25 eV at 87.5% doping. This reduction is mainly attributed to the progressive substitution of Br 4p states by I 5p states near the valence band maximum, which modifies the valence band structure. Differential charge density analysis shows electron transfer from Bi to I, enhancing local polarization effects. Optical property calculations demonstrate a pronounced red shift in the absorption edge and significantly enhanced absorption intensity in the visible region after I doping. The real and imaginary parts of the dielectric function also exhibit red shifts and increased peak intensities in the low-energy region. Gibbs free energy analysis indicates that the Gibbs free energy for *COOH formation decreases from 2.83 eV in the pristine system to 2.68 eV after I doping, while the free energy of the *CO intermediate decreases from 1.28 eV to 0.98 eV, significantly improving the CO₂ reduction pathway. This study provides a theoretical basis for improving the optical response and the thermodynamics of the CO₂ reduction reaction through halogen substitution, suggesting a promising strategy for enhancing the photocatalytic potential of Bi₄O₅Br₂. Full article

(This article belongs to the Special Issue Catalytic Conversion of Small Molecules for Energy and Environmental Sustainability)

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23 pages, 5522 KB

Open AccessArticle

Highly Efficient Oxygen Evolution on the Tubular Array of the Mesoporous NiMoO₄@NiFeS Heterostructure

by Xinyue Hou, Hao Wu, Juan Li, Xiaoyu Jiang, Yacong Zhang and Yongfu Lian

Catalysts 2026, 16(7), 621; https://doi.org/10.3390/catal16070621 - 8 Jul 2026

Abstract

Developing efficient and stable oxygen evolution reaction (OER) electrocatalysts is crucial to the practical application of water electrolysis for hydrogen production. Herein, a tubular array of a mesoporous NiMoO₄@NiFeS heterostructure was anchored on nickel foam through successive hydrothermal processing, liquid etching [...] Read more.

Developing efficient and stable oxygen evolution reaction (OER) electrocatalysts is crucial to the practical application of water electrolysis for hydrogen production. Herein, a tubular array of a mesoporous NiMoO₄@NiFeS heterostructure was anchored on nickel foam through successive hydrothermal processing, liquid etching and direct sulfur vulcanization. The efficient charge transfer, phase transition and full exposure of active sites at the heterostructure’s interfaces, as well as its superhydrophilic surface, endow NiMoO₄@NiFeS with exceptional OER activity. A series of electrochemical experiments indicate that in 1.0 mol·L⁻¹ KOH, NiMoO₄@NiFeS delivers overpotentials as low as 180 and 223 mV at current densities of 10 and 100 mA cm⁻², respectively, and that a Tafel slope of merely 25.9 mV dec⁻¹ is achieved on NiMoO₄@NiFeS, evidencing that the tubular array of the mesoporous NiMoO₄@NiFeS heterostructure significantly facilitates the interfacial transfer of charge/mass and the decrease in the energy barrier of the rate-determining step. This work provides valuable insights for the construction of an efficient and low-cost electrocatalyst with hierarchical mesoporous core–shell structures. Full article

(This article belongs to the Special Issue Catalytic Activity of Two-Dimensional Materials and Their Heterostructures)

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15 pages, 1519 KB

Open AccessArticle

Engineering Oxygen Vacancies in Pt/TiO₂ Catalysts for Efficient Light-Driven Reverse Water-Gas Shift

by Li Fang, Yuxian Jiang, Xueyang Jiang, Qin Zhang, Sihui Suo, Chenhui Zhao, Jiayu Song and Jiancong Liu

Catalysts 2026, 16(7), 620; https://doi.org/10.3390/catal16070620 - 7 Jul 2026

Abstract

Oxygen vacancies are a key factor determining the efficiency of the CO₂ hydrogenation reaction and play a crucial role in CO₂ adsorption and activation. However, effectively regulating the concentration of oxygen vacancies to enhance the performance of the light-driven reverse water [...] Read more.

Oxygen vacancies are a key factor determining the efficiency of the CO₂ hydrogenation reaction and play a crucial role in CO₂ adsorption and activation. However, effectively regulating the concentration of oxygen vacancies to enhance the performance of the light-driven reverse water gas shift (RWGS) reaction remains a challenge. To address this, this study successfully developed Pt/TiO₂ catalysts with varying oxygen vacancy concentrations by controlling the morphology of TiO₂. Structural characterization results indicate that, compared to Pt/TiO₂-NR, Pt/TiO₂-NB exhibits a higher oxygen vacancy (O_V) concentration and greater CO₂ absorption. Catalytic performance evaluation results showed that under an irradiance of 2.5 W/cm², the CO production rates of the Pt/TiO₂-NB catalyst reached 57.03 mol·g_Pt⁻¹·h⁻¹. Furthermore, the catalyst maintained excellent catalytic stability during 45 h of continuous operation, demonstrating good potential for practical applications. Full article

(This article belongs to the Special Issue 15th Anniversary of Catalysts—Recent Advances in Photocatalysis)

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16 pages, 4667 KB

Open AccessArticle

Cerium-Promoted Nickel–Alumina Catalysts for Methane Partial Oxidation: Optimal Loading Strategy for Enhanced Syngas Production

by Ghzzai Almutairi, Norah Alwadai, Wasim Ullah Khan, Fekri Abdulraqeb Ahmed Ali, Mathkar Alharthi, Sami S. Alsaleh, Abdulaziz I. Alromaeh, Bassam Aldraweesh, Mohammed Alsaleh and Ahmed S. Al-Fatesh

Catalysts 2026, 16(7), 619; https://doi.org/10.3390/catal16070619 - 7 Jul 2026

Abstract

Methane partial oxidation (POM) offers a promising pathway for syngas production, but achieving optimal catalyst performance requires precise control of promoter loading. We systematically investigated cerium (Ce) promotion on nickel-based catalysts supported on aluminum oxide (Ni/Al₂O₃) catalysts across 1–3 [...] Read more.

Methane partial oxidation (POM) offers a promising pathway for syngas production, but achieving optimal catalyst performance requires precise control of promoter loading. We systematically investigated cerium (Ce) promotion on nickel-based catalysts supported on aluminum oxide (Ni/Al₂O₃) catalysts across 1–3 wt.% loadings and identified a critical discovery: catalyst performance exhibits a pronounced non-monotonic response to Ce concentration. The 1 wt.% Ce-promoted catalyst (Ni+1Ce/Al) achieved the superior performance with 65% methane conversion and 60% hydrogen yield at 650 °C, maintaining stable output over 275 min time-on-stream. This smaller Ce amount tunes NiO reducibility, oxygen mobility, and metal–support interactions, resulting in improved activity performance of Ni+1Ce/Al. Notably, Ce promotion shifts the H₂/CO ratio from 2.5 to 2.9, with the increased hydrogen yield arising from enhanced water–gas shift chemistry and indirect oxidation pathways. Excess cerium (2–3 wt.%) causes performance deterioration, Ni particle agglomeration, and thus loss of Ni active sites, demonstrating that Ce operates as a structural promoter with a well-defined appropriate concentration window. Moreover, the best performing catalyst (Ni+1Ce/Al) remained stable during 20-h long-term POM. An artificial neural network model achieved exceptional predictive accuracy (R = 0.9758 overall), validating the experimental findings. These results indicate that the best Ce loading for industrial application is 1 wt.% and the traditional alumina supports can be competitive in performance with the advantage of thermal stability and cost-effectiveness when doped with rare-earth elements. Full article

(This article belongs to the Special Issue Effect of the Modification of Catalysts on the Catalytic Performance, 3rd Edition)

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53 pages, 1384 KB

Open AccessReview

Recent Advances in Fe-TiO₂ and rGO-TiO₂ Photocatalysts for Phenolic Wastewater Treatment: Synthesis, Mechanisms, and Applications

by Caressa Munien, Emmanuel Kweinor Tetteh, Sudesh Rathilal and Ajay Kumar Mishra

Catalysts 2026, 16(7), 618; https://doi.org/10.3390/catal16070618 - 6 Jul 2026

Abstract

Phenolic compounds represent a class of highly toxic, bioaccumulative, and persistent pollutants in industrial wastewater. Conventional treatment methods often fail to degrade these recalcitrant pollutants efficiently. Advanced oxidation processes, particularly semiconductor-based heterogeneous photocatalysis utilizing titanium dioxide (TiO₂), have exhibited highly effective [...] Read more.

Phenolic compounds represent a class of highly toxic, bioaccumulative, and persistent pollutants in industrial wastewater. Conventional treatment methods often fail to degrade these recalcitrant pollutants efficiently. Advanced oxidation processes, particularly semiconductor-based heterogeneous photocatalysis utilizing titanium dioxide (TiO₂), have exhibited highly effective strategies for complete pollutant mineralization. Pristine TiO₂ is a widely utilized photocatalyst. However, it is severely constrained by its wide band gap (active only under UV light) and rapid electron–hole recombination rate, restricting its efficiency under visible light for practical applications. Surface modification using iron (Fe) doping and reduced graphene oxide (rGO) coupling with TiO₂ has emerged as a promising strategy to overcome these challenges. Thus, this review evaluates the latest advancements in Fe-TiO₂ and rGO-TiO₂ photocatalysts for phenolic wastewater treatment. The fundamental photocatalytic mechanisms of TiO₂, binary (Fe-TiO₂ and rGO-TiO₂), and ternary (Fe-TiO₂/rGO) composites are examined. Additionally, it evaluates various synthesis techniques, including green synthesis routes, characterization techniques, prospects of Fe and rGO, and real-world application efficacy. Furthermore, a comparative performance matrix evaluates the performance progression from pristine TiO₂ to binary systems, and ultimately to ternary Fe-TiO₂/rGO composites. The ternary configuration exhibits remarkable synergy effects, where iron doping shifts the optical absorption into the visible light spectrum, and rGO acts as an electron sink to suppress recombination. Moreover, the long-term stability and reusability performance, toxicity, commercial capability, and life cycle assessment of the photocatalysts are discussed. Finally, the performance of these composites in real wastewater matrices was examined to determine the gap between laboratory success and industrial viability. Full article

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

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11 pages, 3771 KB

Open AccessArticle

Assembly of Fe₃O₄@SiO₂ Magnetic Nanochains and Application of Glucose Oxidase Immobilized by Nanochains in Flow Injection Chemiluminescence Systems

by Dandan Zhao, Qingran Song, Sijia Sun, Xiaohan Wang, Ping Cheng, Wenjie Wu, Wangkai Cheng, Xianghan Chen and Qiang Zhang

Catalysts 2026, 16(7), 617; https://doi.org/10.3390/catal16070617 - 6 Jul 2026

Abstract

Fe₃O₄ magnetic nanoparticles, as typical magnetic nanomaterials, can be functionalized and self-assembled into one-dimensional and two-dimensional structures to obtain new physicochemical properties. However, there are few studies on preparing stable large-sized one-dimensional Fe₃O₄ magnetic nanochains structure by [...] Read more.

Fe₃O₄ magnetic nanoparticles, as typical magnetic nanomaterials, can be functionalized and self-assembled into one-dimensional and two-dimensional structures to obtain new physicochemical properties. However, there are few studies on preparing stable large-sized one-dimensional Fe₃O₄ magnetic nanochains structure by a simple self-assembly method, and its application scope needs to be expanded urgently. In this paper, a large-size Fe₃O₄@SiO₂ one-dimensional nanochains were synthesized and modified by means of different functionalization. On this basis, the application of one-dimensional nanochains in the flow injection chemiluminescence analysis was explored. Glucose oxidase was immobilized on the Fe₃O₄@SiO₂ nanochains, which as a packed stationary phase, was successfully coupled with the flow injection system through the optimization of experimental conditions. As a result, a novel flow injection chemiluminescence analysis of glucose was developed. It has been proven that the one-dimensional nanochains-based packed stationary phase not only retains similar catalytic sites as the free magnetic particles, but also effectively overcomes the problem of poor fluidity of the free fixed phase. Therefore, it is expected to explore more high-performance flow injection analysis systems by strategies of the nanochain-immobilized enzyme-based packed stationary phase. Full article

(This article belongs to the Topic Advanced Materials in Chemical Engineering)

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22 pages, 2068 KB

Open AccessFeature PaperArticle

Sonochemically Synthesized Pure and Gd₂O₃-Modified ZnO Nanoneedles for Enhanced Degradation of Paracetamol

by Nina Kaneva

Catalysts 2026, 16(7), 616; https://doi.org/10.3390/catal16070616 - 6 Jul 2026

Abstract

Pure ZnO and ZnO/Gd₂O₃ (1 and 2 mol %) nanoneedles were synthesized via a sonochemical route and evaluated as catalytic materials for the degradation of paracetamol using glass and PTFE (Teflon) stirring rods. The morphology and elemental composition of the [...] Read more.

Pure ZnO and ZnO/Gd₂O₃ (1 and 2 mol %) nanoneedles were synthesized via a sonochemical route and evaluated as catalytic materials for the degradation of paracetamol using glass and PTFE (Teflon) stirring rods. The morphology and elemental composition of the obtained nanostructures were investigated by SEM and EDS analyses, confirming the formation of anisotropic rod-like architectures and the successful incorporation of gadolinium species into the ZnO matrix. The optical and defect-related properties were further examined by photoluminescence and UV–Vis spectroscopy, revealing defect-related modifications in the electronic structure and improved charge carrier behavior in the gadolinium-modified samples. Comparative catalytic experiments showed higher degradation efficiencies in the system employing the glass stirring bar compared to the PTFE. However, the differences between these two setups are not limited solely to the stirring bar material, but also involve variations in interfacial contact conditions during operation. Therefore, the observed differences in catalytic activity cannot be attributed to a single mechanistic origin such as mechanically induced effects, but rather reflect the combined influence of catalyst–surface interactions and the specific nature of the stirring medium. The influence of inorganic ions on paracetamol degradation was also investigated using distilled water and aqueous solutions containing sodium chloride, sodium sulfate, and sodium hydrogen carbonate. In both systems, the ZnO/Gd₂O₃ samples exhibited higher degradation efficiency than pristine ZnO, indicating that Gd incorporation plays a key role in enhancing catalytic performance. This improvement can be associated with a modified defect structure and more favorable charge carrier dynamics in the doped material. The mineralization efficiency of the treated solutions was additionally evaluated through chemical oxygen demand (COD) measurements, confirming a significant reduction in organic load after treatment. Full article

(This article belongs to the Special Issue Smart Catalysis: Evolution, Present State and Future Horizons)

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