Catalysts

15 pages, 2053 KiB

Open AccessFeature PaperArticle

Kinetic Understanding of the Enhanced Electroreduction of Nitrate to Ammonia for Co₃O₄–Modified Cu₂₊₁O Nanowire Electrocatalyst

by Hao Yu, Shen Yan, Jiahua Zhang and Hua Wang

Catalysts 2025, 15(5), 491; https://doi.org/10.3390/catal15050491 - 19 May 2025

Abstract

Electrocatalytic nitrate reduction reaction (NO₃⁻RR) to ammonia (NH₃) presents an alternative, sustainable approach to ammonia production. However, the existing catalysts suffer from poor NH₃ yield under lower concentrations of NO₃⁻, and the kinetic understanding [...] Read more.

Electrocatalytic nitrate reduction reaction (NO₃⁻RR) to ammonia (NH₃) presents an alternative, sustainable approach to ammonia production. However, the existing catalysts suffer from poor NH₃ yield under lower concentrations of NO₃⁻, and the kinetic understanding of bimetal catalysis is lacking. In this study, a Co₃O₄–modified Cu₂₊₁O nanowire (CoCuNWs) catalyst with a high specific surface area was synthesized to effectively produce NH₃ from a 10 mM KNO₃ basic solution. CoCuNWs demonstrated a high NH₃ yield rate of 0.30 mmol h⁻¹ cm⁻² with an NH₃ Faradaic efficiency (FE) of 96.7% at −0.2 V vs. RHE, which is 1.5 times higher than the bare Cu₂₊₁O NWs. The synergistic effect between Co₃O₄ and Cu₂₊₁O significantly enhanced both the nitrate conversion and ammonia yield. Importantly, it is revealed that the surface of CoCuNWs is kinetically more easily saturated with NO₃⁻ (NO₂⁻) ions than that of Cu₂₊₁O NWs, as evidenced by both the higher current density and the plateau occurring at higher NO_x⁻ concentrations. In addition, CoCuNWs exhibit a higher diffusion coefficient of NO₃⁻, being 1.6 times higher than that of Cu₂₊₁O NWs, which also indicates that the presence of Co₃O₄ could promote the diffusion and adsorption of NO₃⁻ on CoCuNWs. Moreover, the ATR–SEIRAS analysis was applied to illustrate the reduction pathway of NO₃⁻ to NH₃ on CoCuNWs, which follows the formation of the key intermediate from *NO₂⁻, *NO, *NH₂OH to *NH₃. This work presents a strategy for constructing dual–metal catalysts for NO₃⁻RR and provides an insight to understand the catalysis from the perspective of the kinetics. Full article

(This article belongs to the Special Issue Powering the Future: Advances of Catalysis in Batteries)

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19 pages, 2133 KiB

Open AccessFeature PaperArticle

Electrodeposited Co Crystalline Islands Shelled with Facile Spontaneously Deposited Pt for Improved Oxygen Reduction

by Jelena Golubović, Lazar Rakočević, Vladimir Rajić, Miloš Milović and Svetlana Štrbac

Catalysts 2025, 15(5), 490; https://doi.org/10.3390/catal15050490 - 18 May 2025

Abstract

The cobalt crystalline islands (Co_cryst) were electrochemically deposited onto a glassy carbon (GC) support and then modified by a facile spontaneous deposition of platinum. The electrocatalytic activity of the resulting Co_cryst-Pt core-shell catalyst was evaluated for the oxygen reduction [...] Read more.

The cobalt crystalline islands (Co_cryst) were electrochemically deposited onto a glassy carbon (GC) support and then modified by a facile spontaneous deposition of platinum. The electrocatalytic activity of the resulting Co_cryst-Pt core-shell catalyst was evaluated for the oxygen reduction reaction (ORR) in an alkaline medium. The XRD characterization of the Co_cryst-Pt islands revealed that the cobalt core had a hexagonal close-packed (hcp) crystalline structure, and that the platinum shell exhibited a crystalline structure with a preferential (111) orientation. SEM images showed that the average lateral size of the Co_cryst islands was 1.17 μm, which increased to 1.32 μm after adding platinum. The XPS analysis indicated that the outer layer of the bulk metallic Co_cryst islands was fully oxidized. During the spontaneous deposition of platinum, the outer Co(OH)₂ layer was dissolved, leaving the cobalt core in a metallic state, while the platinum shell remained only partially oxidized. The high electrochemically active surface area of the Co_cryst-Pt/GC electrode, along with a suitable crystalline structure of the Co_cryst-Pt islands, contributes to enhancing its ORR activity by providing a greater number of surface active sites for oxygen adsorption and subsequent reduction. The ORR on the Co_cryst-Pt catalyst occurs via a four-electron reaction pathway, with onset and half-wave potentials of 1.07 V and 0.87 V, respectively, which exceed those of polycrystalline platinum and a commercial benchmark Pt/C. Full article

(This article belongs to the Special Issue Insight into Electrocatalysts for Oxygen Reduction Reaction)

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22 pages, 6513 KiB

Open AccessArticle

Sustainable MgO Nanocatalyst Additives for Boosting Performance and Mitigating Emissions of Used Cooking Oil Biodiesel–Diesel Blends in Compression Ignition Engines

by Kiran Chaudhari, Nilesh Salunke, Shakeelur Raheman Ateequr Raheman, Khursheed B. Ansari, Kapil Ashokrao Saner, Vijay Kashinath Suryawanshi and Mumtaj Shah

Catalysts 2025, 15(5), 489; https://doi.org/10.3390/catal15050489 - 17 May 2025

Abstract

With conventional fuels dwindling and emissions rising, there is a necessity to develop and assess innovative substitute fuel for compression ignition (CI) engines. This study investigates the potential of magnesium oxide (MgO) nanoparticles as a sustainable additive to enhance the performance and reduce [...] Read more.

With conventional fuels dwindling and emissions rising, there is a necessity to develop and assess innovative substitute fuel for compression ignition (CI) engines. This study investigates the potential of magnesium oxide (MgO) nanoparticles as a sustainable additive to enhance the performance and reduce emissions of used cooking oil (UCO) biodiesel–diesel blends in CI engines. MgO nanoparticles were biosynthesized using Citrus aurantium peel extract, offering an environmentally friendly production method. A single-cylinder CI engine was used to test the performance of diesel fuel (B0), a 20% biodiesel blend (B20), and B20 blends with 30 ppm (B20M30) and 60 ppm (B20M60) MgO nanoparticles. Engine performance parameters (brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), and exhaust gas temperature (EGT)) and emission characteristics (CO, NO_x, unburnt hydrocarbons (HCs), and smoke opacity) were measured. The B20M60 blend showed a 2.38% reduction in BSFC and a 3.38% increase in BTE compared to B20, with significant reductions in unburnt HC, CO, and smoke opacity. However, NO_x emissions increased by 6.57%. The green synthesis method enhances sustainability, offering a promising pathway for cleaner and more efficient CI engine operation using UCO biodiesel, demonstrating the effectiveness of MgO nanoparticles. Full article

(This article belongs to the Special Issue Waste-to-Resources Through Catalysis in Green and Sustainable Way)

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16 pages, 649 KiB

Open AccessArticle

Research on Catalysts for Online Ammonia Hydrogen Production in Marine Engines: Performance Evaluation and Reaction Kinetic Modeling

by Jin Wu, Liang Yang, Chuang Xiang, Junjie Liang, He Yang, Dilong Li, Ying Sun, Lin Lv and Neng Zhu

Catalysts 2025, 15(5), 488; https://doi.org/10.3390/catal15050488 - 17 May 2025

Abstract

One viable technical approach for achieving hydrogen-blended combustion in marine ammonia-fueled engines is to utilize online ammonia decomposition to produce hydrogen, which is then introduced into the engine for combustion. This work carried out ammonia decomposition experiments using various catalysts, examining the effects [...] Read more.

One viable technical approach for achieving hydrogen-blended combustion in marine ammonia-fueled engines is to utilize online ammonia decomposition to produce hydrogen, which is then introduced into the engine for combustion. This work carried out ammonia decomposition experiments using various catalysts, examining the effects of temperature and space velocity on Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 and Ni/Ce_0.36Zr_0.64O₂ catalysts. Based on the experimental data obtained, the kinetic parameters of ammonia decomposition were fitted using four different models: mass action law, first-order reaction, Langmuir, and Temkin–Pyzhev kinetics across two catalysts, with the subsequent mechanistic analysis of catalytic reaction processes within the reactor. The results revealed that the NH₃ conversion rate of the Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 catalyst was superior to that of the Ni/Ce_0.36Zr_0.64O₂ catalyst, with temperature activity windows of 250–450 °C and 400–600 °C, respectively. Within the range of 2000–32,000 mL·g⁻¹·h⁻¹), an increase in space velocity led to a decrease in NH₃ conversion rate by approximately half. All four models were able to predict NH₃ conversion rates for the different catalysts with reasonable accuracy. The activation energies for Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 and Ni/Ce_0.36Zr_0.64O₂ catalysts were found to be 37.7 kJ·mol⁻¹ and 66 kJ·mol⁻¹, respectively. Targeting hydrogen requirements of 10–40% vol for ammonia engines, the corresponding catalytic temperatures for Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 and Ni/Ce_0.36Zr_0.64O₂ were above 267 °C and 500 °C, respectively. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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11 pages, 2195 KiB

Open AccessArticle

Highly Dispersed Pt on TiO_x Embedded in Porous Carbon as Electrocatalyst for Hydrogen Evolution Reaction

by Zihan Wei, Xin Chen, Pengfei Diao, Jiayi Liao, Zhaonan Chong, Change Yao, Zhong Ma and Guisheng Li

Catalysts 2025, 15(5), 487; https://doi.org/10.3390/catal15050487 - 17 May 2025

Abstract

In conventionally used carbon-supported heterogeneous platinum catalysts for hydrogen evolution reaction (HER), low Pt utilization efficiency and poor stability, resulting from weak interactions with the carbon supports, are crucial issues. Here, we report a novel hierarchical structure of TiO_x nanoparticles embedded in [...] Read more.

In conventionally used carbon-supported heterogeneous platinum catalysts for hydrogen evolution reaction (HER), low Pt utilization efficiency and poor stability, resulting from weak interactions with the carbon supports, are crucial issues. Here, we report a novel hierarchical structure of TiO_x nanoparticles embedded in porous carbon with the in situ growth of highly dispersed Pt on the TiO_x surface (Pt-TiO_x@C). The as-prepared Pt-TiO_x@C electrocatalyst showed excellent catalytic activity during HER with an overpotential of only 10 mV when the current density reached 10 mA cm⁻² and the mass activity was 9.24 A mg_Pt⁻¹ at an overpotential of 30 mV in 0.5 M H₂SO₄ solution, thus outperforming commercial Pt/C catalysts. Furthermore, it also exhibited highly stable catalytic activity over 10,000 CV cycles of an accelerated degradation test (ADT). This high HER activity and durability could be ascribed to the highly dispersed Pt feature and the strong metal–support interaction (SMSI) between Pt and TiO_x. This study also provides a simple and effective method for designing highly active and stable electrocatalysts. Full article

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15 pages, 5139 KiB

Open AccessArticle

Synchronous Removal of Organic Pollutants and Phosphorus from Emergency Wastewater in Chemical Industry Park by Plasma Catalysis System Based on Calcium Peroxide

by Aihua Li, Chengjiang Qian, Jinfeng Wen and Tiecheng Wang

Catalysts 2025, 15(5), 486; https://doi.org/10.3390/catal15050486 - 16 May 2025

Abstract

This study employs a plasma-coupled calcium peroxide (CaO₂) system to degrade tetracycline (TC) and remove phosphorus from emergency wastewater in a chemical industry park. The plasma/CaO₂ system achieves optimal performance when the CaO₂ dosage reaches 0.13 g/L. Higher degradation [...] Read more.

This study employs a plasma-coupled calcium peroxide (CaO₂) system to degrade tetracycline (TC) and remove phosphorus from emergency wastewater in a chemical industry park. The plasma/CaO₂ system achieves optimal performance when the CaO₂ dosage reaches 0.13 g/L. Higher degradation efficiencies of TC were observed at increased discharge voltages, frequencies, and under weakly acidic and weakly alkaline conditions. Variations in discharge voltage and frequency have no significant impact on the phosphorus removal efficiency, but weakly alkaline conditions favor phosphorus removal. The reactive species (·OH, ¹O₂, O₂·⁻) within the plasma/CaO₂ system were identified, and their roles were elucidated using radical scavengers. Subsequently, the degradation process was characterized by measuring changes in total organic carbon (TOC), chemical oxygen demand (COD), and ammonia nitrogen during the reaction, along with three-dimensional fluorescence analysis and ultraviolet-visible spectroscopy (UV-Vis). Eight intermediate products were identified through LC-MS, and two degradation pathways were clarified based on density functional theory. The toxicity analysis of the intermediate products demonstrated that the plasma/CaO₂ system is an efficient, feasible, and environmentally friendly method for the synchronous removal of organic pollutants and phosphorus from emergency wastewater in a chemical industry park. Full article

(This article belongs to the Special Issue Plasma Catalysis for Environment and Energy Applications)

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21 pages, 2799 KiB

Open AccessFeature PaperArticle

Exploring Perhydro-Benzyltoluene Dehydrogenation Using Sulfur-Doped PtMo/Al₂O₃ Catalysts

by Kevin Alconada, Fatima Mariño, Ion Agirre and Victoria Laura Barrio

Catalysts 2025, 15(5), 485; https://doi.org/10.3390/catal15050485 - 16 May 2025

Abstract

This study investigates the dehydrogenation of perhydrobenzyltoluene, a Liquid Organic Hydrogen Carrier (LOHC), using sulfur-doped bimetallic PtMo/Al₂O₃ catalysts. Based on previous research that highlighted the superior performance of PtMo catalysts over monometallic Pt catalysts, this work focuses on minimizing byproduct [...] Read more.

This study investigates the dehydrogenation of perhydrobenzyltoluene, a Liquid Organic Hydrogen Carrier (LOHC), using sulfur-doped bimetallic PtMo/Al₂O₃ catalysts. Based on previous research that highlighted the superior performance of PtMo catalysts over monometallic Pt catalysts, this work focuses on minimizing byproduct formation, specifically methylfluorene, through sulfur doping. Catalysts with low platinum content (<0.3 wt.%) were synthesized using the wet impregnation method by varying sulfur concentrations to study their impact on catalytic activity. Characterization techniques, including CO–DRIFT and CO–TPD, revealed the role of sulfur in selectively blocking low-coordinated Pt sites, thus improving selectivity and maintaining high dispersion. Catalytic tests revealed that samples with ≥0.1 wt.% sulfur achieved up to a threefold reduction in methylfluorene formation compared to the unpromoted PtMo/Al₂O₃ sample, with a molar fraction below 2% at 240 min. In parallel, these samples reached a degree of dehydrogenation (DoD) above 85% within 240 min, demonstrating that improved selectivity can be achieved without compromising catalytic performance. Full article

(This article belongs to the Special Issue Catalysts for Energy Storage)

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16 pages, 3297 KiB

Open AccessArticle

Cu-Sn Electrocatalyst Prepared with Chemical Foaming and Electroreduction for Electrochemical CO₂ Reduction

by Caibo Zhu, Ao Yu, Yin Zhang, Wenbo Chen, Zhijian Wu, Manni Xu, Deyu Qu, Junxin Duan and Xi Li

Catalysts 2025, 15(5), 484; https://doi.org/10.3390/catal15050484 - 16 May 2025

Abstract

The conversion of CO₂ through the electrochemical reduction reaction (ECO₂RR) into chemicals or fuels is regarded as one of the effective ways to decrease atmospheric CO₂ concentrations. In this study, a Cu-Sn bimetallic electrocatalyst (ER-Sn_mCu_nO [...] Read more.

The conversion of CO₂ through the electrochemical reduction reaction (ECO₂RR) into chemicals or fuels is regarded as one of the effective ways to decrease atmospheric CO₂ concentrations. In this study, a Cu-Sn bimetallic electrocatalyst (ER-Sn_mCu_nO_x-t/CC) was successfully prepared via a chemical foaming method and electrochemical reduction. SEM showed that ER-Sn₁Cu₁O_x-500 nanoparticles were uniformly distributed on the carbon cloth, which benefited from foaming. The XPS results demonstrated the synergistic interaction between Cu and Sn and the existence of oxygen vacancies originating from the electroreduction. Due to the above features, ER-Sn₁Cu₁O_x-500/CC achieved 84.1% FE for HCOOH at −1.1 V vs. RHE, and the corresponding J_HCOOH was up to 32.4 mA·cm⁻² in the H-type cell. Especially in the flow cell, ER-Sn₁Cu₁O_x-500/GDE could reach a high J_HCOOH of 190 mA·cm⁻² at −1.1 V vs. RHE and maintained J_HCOOH higher than 100 mA·cm⁻² for 24 h with a formic acid selectivity over 70%, indicating both excellent catalytic activity and high HCOOH selectivity. In situ FTIR results revealed that synergism between Cu and Sn could regulate the adsorption of intermediates, thus enhancing the catalytic performance of ER-Sn₁Cu₁O_x-500 for ECO₂RR. Full article

(This article belongs to the Section Electrocatalysis)

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16 pages, 1982 KiB

Open AccessArticle

Selective Catalytic Reduction of NO with H₂ over Pt/Pd-Containing Catalysts on Silica-Based Supports

by Magdalena Jabłońska, Adrián Osorio Hernández, Jürgen Dornseiffer, Jacek Grams, Anqi Guo, Ulrich Simon and Roger Gläser

Catalysts 2025, 15(5), 483; https://doi.org/10.3390/catal15050483 - 15 May 2025

Abstract

Platinum- and/or palladium-containing silica-based supports were applied for the selective catalytic reduction of NO_x with hydrogen (H₂-SCR-DeNO_x). To obtain enhanced activity and N₂ selectivity below 150 °C, we varied the type and loading of noble metals (Pt [...] Read more.

Platinum- and/or palladium-containing silica-based supports were applied for the selective catalytic reduction of NO_x with hydrogen (H₂-SCR-DeNO_x). To obtain enhanced activity and N₂ selectivity below 150 °C, we varied the type and loading of noble metals (Pt and Pd both individually and paired, 0.1–1.0 wt.-%), silica-containing supports (ZrO₂/SiO₂, ZrO₂/SiO₂/Al₂O₃, Al₂O₃/SiO₂/TiO₂), as well as the H₂ concentration in the feed (2000–4000 ppm). All of these contributed to enhancing N₂ selectivity during H₂-SCR-DeNO_x over the (0.5 wt.-%)Pt/Pd/ZrO₂/SiO₂ catalyst in the presence of 10 vol.-% of O₂. H₂ was completely consumed at 150 °C. A comparison of the catalytic results obtained during H₂-SCR-DeNO_x,(H₂-)NH₃-SCR-DeNO_x, as well as stop-flow H₂-SCR-DeNO_x and temperature-programmed studies, revealed that in the temperature range between 150 and 250 °C, the continuously coupled or overlaying mechanism of NO reduction by hydrogen and ammonia based on NH₃ formation at lower temperatures, which is temporarily stored at the acid sites of the support and desorbed in this temperature range, could be postulated. Full article

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

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12 pages, 1865 KiB

Open AccessFeature PaperArticle

Efficient Synthesis of Tetrasubstituted Furans via Lipase-Catalyzed One-Pot Sequential Multicomponent Reaction

by Yongqi Zeng, Yong Tang, Minglu Xu, Dantong Wang, Zhi Wang, Yin Gao and Lei Wang

Catalysts 2025, 15(5), 482; https://doi.org/10.3390/catal15050482 - 15 May 2025

Abstract

Tetrasubstituted furans and their derivatives represent a versatile class of important heterocyclic frameworks widely distributed in natural products. These scaffolds also demonstrate significant potential in pharmaceutical chemistry, materials science, and organic synthesis methodologies. In this study, we successfully established a synergistic catalytic system [...] Read more.

Tetrasubstituted furans and their derivatives represent a versatile class of important heterocyclic frameworks widely distributed in natural products. These scaffolds also demonstrate significant potential in pharmaceutical chemistry, materials science, and organic synthesis methodologies. In this study, we successfully established a synergistic catalytic system utilizing benzoylacetonitriles, aldehydes, and benzoyl chlorides as substrates, facilitated by tributylphosphine and immobilized lipase (Novozym 435), to achieve efficient synthesis of cyano-containing tetrasubstituted furans. Under optimized conditions, we obtained a series of target products exhibiting exceptional substrate tolerance with good to excellent isolated yields ranging from 80% to 94%. Additionally, we proposed a reasonable reaction mechanism and verified it through controlled experiments. This methodology not only expands the synthetic utility of lipase in non-natural transformations but also establishes a paradigm of green chemistry for the construction of tetrasubstituted furans. Full article

(This article belongs to the Special Issue Enzyme and Biocatalysis Application)

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25 pages, 1620 KiB

Open AccessFeature PaperArticle

Laccase-Catalyzed Polymerized Natural Bioactives for Enhanced Mushroom Tyrosinase Inhibition

by Diana Costa, Diana Rocha, Joana Santos, Jennifer Noro, Artur Ribeiro and Carla Silva

Catalysts 2025, 15(5), 481; https://doi.org/10.3390/catal15050481 - 14 May 2025

Abstract

Skin hyperpigmentation disorders, such as melasma, are linked to excessive melanin production, primarily regulated by the enzyme tyrosinase (TYR). While current inhibitors like kojic acid (KA) are effective, they often cause adverse side effects, driving the search for safer andnatural alternatives. This study [...] Read more.

Skin hyperpigmentation disorders, such as melasma, are linked to excessive melanin production, primarily regulated by the enzyme tyrosinase (TYR). While current inhibitors like kojic acid (KA) are effective, they often cause adverse side effects, driving the search for safer andnatural alternatives. This study evaluated the TYR inhibitory potential of bioactive-rich extracts from acorn, cocoa, cork, and eucalyptus, extracted using hydroethanolic (HE) and natural deep eutectic solvents (NADES), and explored the enhancement of their bioactivity through laccase-assisted polymerization. NADES significantly improved extraction yields and preserved bioactive compounds, with cocoa extracts showing the highest TYR inhibition. Laccase-mediated polymerization further enhanced TYR inhibitory activity, particularly of NADES extracts, suggesting a more effective and sustainable approach for skincare applications. The results highlight the potential of combining green chemistry principles with enzymatic catalysis to develop eco-friendly and efficient treatments for hyperpigmentation disorders, offering a promising alternative to conventional methods. Full article

(This article belongs to the Special Issue The Design of Protein-Based Catalysts)

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9 pages, 8032 KiB

Open AccessFeature PaperArticle

Cyclic Stability of a Bifunctional Catalyst in the Sorption-Enhanced Reverse Water–Gas Shift Reaction

by Johannis A. Z. Pieterse, Saskia Booneveld, Gerard D. Elzinga, Vladimir Dikic, Galina Skorikova, Jurriaan Boon and Andreas Geisbauer

Catalysts 2025, 15(5), 480; https://doi.org/10.3390/catal15050480 - 13 May 2025

Abstract

Sorption-enhanced reverse water–gas shift (SE-RWGS), designated as COMAX, was studied using a Pt4A bifunctional catalyst (reactive adsorbent). The bifunctional Pt4A catalyst integrates CO₂ activation and reaction with water adsorption functionality, where the active phase is loaded onto a carrier that provides a [...] Read more.

Sorption-enhanced reverse water–gas shift (SE-RWGS), designated as COMAX, was studied using a Pt4A bifunctional catalyst (reactive adsorbent). The bifunctional Pt4A catalyst integrates CO₂ activation and reaction with water adsorption functionality, where the active phase is loaded onto a carrier that provides a surface area for Pt dispersion as well as H₂O adsorption capacity. The 0.3 wt% Pt-4A molecular sieve reactive sorbent was tested at a kg scale in a pressure swing (reactive) adsorption–regeneration process. More than 400 cycles over 50 days of operation were successfully demonstrated without significant decay. Cyclic stability was achieved, provided that the regeneration temperature was sufficiently high to ensure near-complete dehydration. The single-bead structure withstood the pressure swing operation effectively, with only a maximum of 2% of the total recovered reactive sorbent turning to fines (<500 μm). The successful integration of catalytic activity and water adsorption capacity into a single particle presents opportunities for the further intensification of sorption-enhanced reactions for CO₂ conversion. Full article

(This article belongs to the Special Issue Catalytic Activity on Thermochemical and Non-Thermal Plasma Conversion/Utilization of Methane and Carbon Dioxide)

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25 pages, 8285 KiB

Open AccessFeature PaperArticle

Active Ag-, Fe-, and AC-Modified TiO₂ Mesoporous Photocatalysts for Anionic and Cationic Dye Degradation

by Daniela Negoescu, Irina Atkinson, Mihaela Gherendi, Daniela C. Culita, Adriana Baran, Simona Petrescu, Veronica Bratan and Viorica Parvulescu

Catalysts 2025, 15(5), 479; https://doi.org/10.3390/catal15050479 - 13 May 2025

Abstract

TiO₂ mesoporous supports were obtained by the sol–gel method from different precursors (titaniumethoxide, isopropoxide, or butoxide) in the presence of nonionic, cationic, and anionic surfactants. Among these samples, those obtained from Ti isopropoxide, Brij58 w/o activated carbon (AC), were selected as supports. [...] Read more.

TiO₂ mesoporous supports were obtained by the sol–gel method from different precursors (titaniumethoxide, isopropoxide, or butoxide) in the presence of nonionic, cationic, and anionic surfactants. Among these samples, those obtained from Ti isopropoxide, Brij58 w/o activated carbon (AC), were selected as supports. Photocatalysts were obtained by modifying these supports with Ag, Fe, and AgFe (each metal around 1% mass). The characterization results showed a stronger influence of titania precursors, surfactants, and AC on the texture and an insignificant effect on the crystalline structure and morphology of the obtained materials. X-ray photoelectron spectroscopy revealed the effects of AC and Fe on the Ag⁰ concentration and of Ag on Fe-reduced species. Based on this information, the results obtained by H₂-TPR, UV–Vis, Raman, and photoluminescence spectroscopy were explained. The performance of the photocatalysts was evaluated in the degradation of Congo Red (CR) and Crystal Violet (CV) dyes under UV and visible light. The Ag-TiO₂ sample exhibited the best activity in degrading CR at acidic pH and in degrading CV under basic conditions. In visible light, we observed the significant effects of the surface plasmon resonance, AC, Ag, and Fe on the activity in CR photodegradation. The proposed kinetics and mechanisms complete the study of the reactions. Full article

(This article belongs to the Special Issue Effect of the Modification of Catalysts on the Catalytic Performance, 2nd Edition)

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15 pages, 4407 KiB

Open AccessArticle

Sustainable Hydrogen from Methanol: NiCuCe Catalyst Design with CO₂-Driven Regeneration for Carbon-Neutral Energy Systems

by Yankun Jiang, Liangdong Zhao and Siqi Li

Catalysts 2025, 15(5), 478; https://doi.org/10.3390/catal15050478 - 13 May 2025

Abstract

This study addresses energy transition challenges through the development of NiCuCe catalysts for high-purity hydrogen production via methanol decomposition, with carbon deposition issues mitigated by CO₂-assisted regeneration. As fossil fuel depletion advances and the urgency of climate change increases, methanol-derived hydrogen [...] Read more.

This study addresses energy transition challenges through the development of NiCuCe catalysts for high-purity hydrogen production via methanol decomposition, with carbon deposition issues mitigated by CO₂-assisted regeneration. As fossil fuel depletion advances and the urgency of climate change increases, methanol-derived hydrogen (CH₃OH → CO + 2H₂) emerges as a carbon-neutral alternative to conventional fossil fuel-based energy systems. The catalyst’s dual Cu²⁺/Ni²⁺ active sites facilitate selective C–O bond cleavage, achieving more than 80% methanol conversion at temperatures exceeding 280 °C without the need for fossil methane inputs. Crucially, CO₂ gasification enables catalyst regeneration through the conversion of 90% carbon deposits into reusable media, circumventing energy-intensive combustion processes. This dual-function system couples carbon capture to hydrogen infrastructure, thereby stabilizing production while valorizing waste CO₂. This innovation minimizes reliance on rare metals through efficient regeneration cycles, mitigating resource constraints during energy crises. Full article

(This article belongs to the Special Issue Catalytic Gasification)

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45 pages, 19249 KiB

Open AccessFeature PaperReview

Multidimensional Engineering of Nanoconfined Catalysis: Frontiers in Carbon-Based Energy Conversion and Utilization

by Qimin Fang, Qihan Sun, Jinming Ge, Haiwang Wang and Jian Qi

Catalysts 2025, 15(5), 477; https://doi.org/10.3390/catal15050477 - 12 May 2025

Abstract

Amid global efforts toward carbon neutrality, nanoconfined catalysis has emerged as a transformative strategy to address energy transition challenges through precise regulation of catalytic microenvironments. This review systematically examines recent advancements in nanoconfined catalytic systems for carbon-based energy conversion (CO₂, CH [...] Read more.

Amid global efforts toward carbon neutrality, nanoconfined catalysis has emerged as a transformative strategy to address energy transition challenges through precise regulation of catalytic microenvironments. This review systematically examines recent advancements in nanoconfined catalytic systems for carbon-based energy conversion (CO₂, CH₄, etc.), highlighting their unique capability to modulate electronic structures and reaction pathways via quantum confinement and interfacial effects. By categorizing their architectures into dimension-oriented frameworks (1D nanotube channels, 2D layered interfaces, 3D core-shell structures, and heterointerfaces), we reveal how geometric constraints synergize with mass/electron transfer dynamics to enhance selectivity and stability. Critical optimization strategies—including heteroatom doping to optimize active site coordination, defect engineering to lower energy barriers, and surface modification to tailor local microenvironments—are analyzed to elucidate their roles in stabilizing metastable intermediates and suppressing catalyst deactivation. We further emphasize the integration of machine learning, in situ characterization, and modular design as essential pathways to establish structure–activity correlations and accelerate industrial implementation. This work provides a multidimensional perspective bridging fundamental mechanisms with practical applications to advance carbon-neutral energy systems. Full article

(This article belongs to the Collection Catalytic Conversion and Utilization of Carbon-Based Energy)

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26 pages, 5961 KiB

Open AccessArticle

Structural Features Underlying the Mismatch Between Catalytic and Cytostatic Properties in L-Asparaginase from Rhodospirillum rubrum

by Igor D. Zlotnikov, Anastasia N. Shishparyonok, Marina V. Pokrovskaya, Svetlana S. Alexandrova, Dmitry D. Zhdanov and Elena V. Kudryashova

Catalysts 2025, 15(5), 476; https://doi.org/10.3390/catal15050476 - 12 May 2025

Abstract

The underlying structural features of the mismatch between catalytic and cytostatic properties in L-asparaginase from Rhodospirillum rubrum (RrA) and three of its mutants were investigated. The rationale for selecting the specific mutations (RrA_{A64V, E67K}; RrA_{R118H, G120R}; RrA_{E149R, V150P,} [...] Read more.

The underlying structural features of the mismatch between catalytic and cytostatic properties in L-asparaginase from Rhodospirillum rubrum (RrA) and three of its mutants were investigated. The rationale for selecting the specific mutations (RrA_{A64V, E67K}; RrA_{R118H, G120R}; RrA_{E149R, V150P, F151T}) is to elucidate the role of inter-subunit interaction in RrA and its impact on catalytic efficiency and stability. Bioinformatic modeling revealed a predominantly negative surface charge on RrA with limited positive charge clusters in the vicinity of the interface region. Thus, some negatively charged groups were replaced with positively charged ones to enhance the electrostatic interactions and stabilize the enzyme quaternary structure. RrA_{A64V, E67K} and RrA_{R118H, G120R} additionally contained an N-terminal 17-amino acid capsid peptide derived from the bacteriophage T7 (MASMTGGQQMGRGSSRQ), which could potentially affect the conformational stability of theenzymes. Circular dichroism (CD) spectroscopy was applied to the kinetic parameters analysis of Asn hydrolysis and showed that native RrA displayed a V_max of 30 U/mg and a K_M of 4.5 ± 0.5 mM. RrA_{E149R, V150P, and F151T} exhibited a substantially increased V_max of 57 U/mg. The catalytic efficiency of V_max/K_M also improved compared to the native enzyme: the V_max/K_M increased from approximately 7 U/mg × mM⁻¹ (for the native enzyme) to 9 U/mg × mM⁻¹ for Mut3. Other mutants exhibited less pronounced changes. Thermo-denaturation studies allowed us to determine the phase transition parameters of the RrA variants in comparison with commercial reference sample EcA. RrA_{A64V, E67K} and RrA_{R118H, G120R} exhibited the most favorable phase transition parameters, with melting temperatures (T_m) of 60.3 °C and 59.4 °C, respectively, exceeding that of the wild-type RrA (54.6 °C) and RrA_{E149R, V150P, F151T} (52 °C). The EcA demonstrated a slightly superior thermal stability, with a T_m of 62 °C. The mutations showed a significant effect on protein stability during trypsinolysis. Therefore, RrA_{E149R, V150P, F151T} showed higher resistance (45% activity remaining after 30 min of trypsin exposure) compared to the native RrA retained 20% activity. EcA preparations exhibited lower stability to trypsinolysis (losing over 90% activity in 15 min). The cytostatic effects were evaluated using MTT assays against K562 (leukemic) and A549 (lung carcinoma) cell lines. The MTT assays with K562 cells revealed that RrA_{E149R, V150P, F151T} (IC₅₀ of 10 U/mL) and RrA_{R118H, G120R} (IC₅₀ of 11.5 U/mL) exhibited superior antiproliferative activity compared to native enzymes RrA (IC₅₀ of 15 U/mL) and EcA (24 U/mL). RrA_{E149R, V150P, F151T} showed the most significant improvement in cytostatic activity. The results obtained indicate that the substitutions in RrA_{E149R, V150P, F151T} resulted in the improvement of the enzyme biocatalytic properties and an increase in the resistance to aggregation and trypsinolysis. This highlights the role of electrostatic interactions in stabilizing the oligomeric structure of the enzyme, which eventually translates into an improvement in cytostatic efficiency and antiproliferative forces. Full article

(This article belongs to the Section Biocatalysis)

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18 pages, 3933 KiB

Open AccessArticle

Ru Nanoparticle Assemblies Modified with Single Mo Atoms for Hydrogen Evolution Reactions in Seawater Electrocatalysis

by Shuhan Wang, Jiani Qin, Yong Zhang, Shuai Chen, Wenjun Yan, Haiqing Zhou and Xiujun Fan

Catalysts 2025, 15(5), 475; https://doi.org/10.3390/catal15050475 - 12 May 2025

Abstract

Ru-based catalysts manifest unparalleled hydrogen evolution reaction (HER) performance, but the hydrolysis of Ru species and the accumulation of corresponding reaction intermediates greatly limit HER activity and stability. Herein, Ru nanoparticle assemblies modified with single Mo atoms and supported on N-incorporated graphene (referred [...] Read more.

Ru-based catalysts manifest unparalleled hydrogen evolution reaction (HER) performance, but the hydrolysis of Ru species and the accumulation of corresponding reaction intermediates greatly limit HER activity and stability. Herein, Ru nanoparticle assemblies modified with single Mo atoms and supported on N-incorporated graphene (referred to as MoRu-NG) are compounded via hydrothermal and chemical vapor deposition (CVD) methods. The incorporation of single Mo atoms into Ru lattices modifies the local atomic milieu around Ru centers, significantly improving HER catalytic behavior and stability. More specifically, MoRu-NG achieves overpotentials of 53 mV and 28 mV at 10 mA cm⁻², with exceptional stability in acidic and alkaline seawater solutions, respectively. In MoRu-NG, Ru atoms have a special electronic structure and thus possess optimal hydrogen adsorption energy, which indicates that excellent HER activity mainly hinges upon Ru centers. To be specific, the d-electron orbitals of Ru atoms are close to half full, giving Ru atoms moderate bond energy for the assimilation and release of hydrogen, which is beneficial for the conversion of reaction intermediates. Moreover, the incorporation of single Mo atoms facilitates the formation of O and O’-bidentate ligands, significantly enhancing the structural stability of MoRu-NG in universal-pH seawater electrolysis. This work advances a feasible construction method of hexagonal octahedral configuration (Ru-O-Mo-N-C) and provides a route to synthesize an efficient and stable catalyst for electrocatalytic HER in universal-pH seawater. Full article

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18 pages, 4175 KiB

Open AccessArticle

Co-Doped Ni@Ni(OH)₂ Core–Shell Catalysts for Dual-Function Water and Urea Oxidation

by Saba A. Aladeemy, Maged N. Shaddad, Talal F. Qahtan, Abdulrahman I. Alharthi, Kamal Shalabi, Abdullah M. Al-Mayouf and Prabhakarn Arunachalam

Catalysts 2025, 15(5), 474; https://doi.org/10.3390/catal15050474 - 12 May 2025

Abstract

Crystalline–amorphous core–shell-like heterostructures have attracted considerable attention in electrocatalysis due to their unique electronic and structural properties; however, tuning the surface composition of the amorphous shell remains a major challenge. In this work, we report a simple, low-cost, one-pot hydrazine-assisted chemical deposition method [...] Read more.

Crystalline–amorphous core–shell-like heterostructures have attracted considerable attention in electrocatalysis due to their unique electronic and structural properties; however, tuning the surface composition of the amorphous shell remains a major challenge. In this work, we report a simple, low-cost, one-pot hydrazine-assisted chemical deposition method for synthesizing a series of Co-doped Ni@Ni(OH)₂ catalysts with a crystalline Ni core and an amorphous Ni(OH)₂ shell. Among the prepared catalysts, the sample containing 10 wt.% cobalt (denoted as b-Co-doped Ni@Ni(OH)₂) exhibited the highest electrocatalytic activity toward both the oxygen evolution reaction (OER) and the urea oxidation reaction (UOR). In 1.0 M KOH, the b-Co-doped Ni@Ni(OH)₂ catalyst achieved a 40 mV lower overpotential at 50 mA·cm⁻² compared to undoped Ni@Ni(OH)₂ for the OER. For the UOR in 0.33 M urea/1.0 M KOH, it delivered approximately twice the anodic current density relative to the undoped sample, along with improved reaction kinetics as evidenced by a Tafel slope of 70.7 mV·dec⁻¹. This performance enhancement is attributed to the optimized core–shell-like architecture, cobalt doping-induced electronic modulation, increased electrochemically active surface area, and improved charge transfer efficiency. Overall, this study demonstrates a promising and scalable strategy for designing advanced Ni-based bifunctional catalysts for sustainable energy conversion and wastewater treatment applications. Full article

(This article belongs to the Special Issue Nanocatalysis: Integrating Sustainability and Innovation Across Diverse Applications)

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33 pages, 6057 KiB

Open AccessFeature PaperReview

Evaluating Theoretical Approaches to Nitrogen-Doped Carbon Supports

by Vu Nguyen and Shubham Vyas

Catalysts 2025, 15(5), 473; https://doi.org/10.3390/catal15050473 - 11 May 2025

Abstract

Catalysis requires extrapolations from computational models to the catalytic activity observed under practical operating conditions, especially for single-atom catalysts, to be made. Thus, it is necessary to understand the fundamental interactions at an atomistic level to rationally design systems for targeted practical applications. [...] Read more.

Catalysis requires extrapolations from computational models to the catalytic activity observed under practical operating conditions, especially for single-atom catalysts, to be made. Thus, it is necessary to understand the fundamental interactions at an atomistic level to rationally design systems for targeted practical applications. With that in mind, the key aspects and parameterization of these model systems are especially important as they will heavily affect the validity of those extrapolations. Rigorously developed models and protocols with well-defined and understood metrics and interactions are reviewed to begin to provide an overview of the best theoretical practices for designing nitrogen-doped carbon supports. Full article

(This article belongs to the Special Issue Single-Atom Catalysts: Current Trends, Challenges, and Prospects)

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