Catalysts

16 pages, 4142 KiB

Open AccessArticle

Preparation of Novel ACE Inhibitory Peptides from Skimmed Goat Milk Hydrolyzed by Multi-Enzymes: Process Optimization, Purification, and Identification

by Wenjing Hu, Guowei Shu, Huan Lei, Guanli Du, Zhengxin Liu and Li Chen

Catalysts 2025, 15(2), 140; https://doi.org/10.3390/catal15020140 (registering DOI) - 3 Feb 2025

Abstract

This study optimizes the process conditions for preparing angiotensin-converting enzyme (ACE) inhibitory peptides from skimmed goat milk (SGM) hydrolyzed by multi-enzymes using response surface methodology. When the enzymatic hydrolysis time was 90 min, the optimal hydrolysis conditions were a pH of 8.49, enzyme-to-substrate [...] Read more.

This study optimizes the process conditions for preparing angiotensin-converting enzyme (ACE) inhibitory peptides from skimmed goat milk (SGM) hydrolyzed by multi-enzymes using response surface methodology. When the enzymatic hydrolysis time was 90 min, the optimal hydrolysis conditions were a pH of 8.49, enzyme-to-substrate ratio (E/S ratio) of 8.04%, and temperature of 61.54 °C. The hydrolysis degree and ACE inhibitory activity were 65.39% ± 0.01% and 84.65% ± 0.03%, respectively. After purification by ultrafiltration, macroporous resin, and gel filtration, the ACE inhibitory activity of F2-2 in the two components of F2 was higher, with the ACE inhibitory rate of 93.97% ± 0.15% and IC₅₀ of 0.121 ± 0.004 mg/mL. The content of hydrophobic amino acids, fatty amino acids, and aromatic amino acids in component F2-2 accounts for 73.17%, 33.86%, and 33.72%, respectively. Eleven peptides were isolated and identified from the F2-2 components of the enzymatic hydrolysate of SGM, including two peptides without an established database. The peptides mainly came from β casein, α_S1 casein, and α_S2 casein. Full article

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

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12 pages, 4747 KiB

Open AccessArticle

Sulfur Dioxide-Tolerant Core@shell Ru@Pt Catalysts Toward Oxygen Electro-Reduction

by Yuxin Liu, Changyuan Bao, Guodong Xu, Lei Du and Bing Huang

Catalysts 2025, 15(2), 139; https://doi.org/10.3390/catal15020139 - 3 Feb 2025

Abstract

Proton exchange membrane fuel cells (PEMFCs) have achieved milestones in performance improvements and commercial launches. In the typical commercialized PEMFCs, the compressed air to cathode is usually supplied from ambient air, assuming that no costly pre-purification system is applied. Therefore, the working PEMFCs [...] Read more.

Proton exchange membrane fuel cells (PEMFCs) have achieved milestones in performance improvements and commercial launches. In the typical commercialized PEMFCs, the compressed air to cathode is usually supplied from ambient air, assuming that no costly pre-purification system is applied. Therefore, the working PEMFCs may suffer from the negative effects of the air impurities. In this regard, SO₂, as the most poisonous species, may be fed along with air at the cathode and strongly adsorbed on the Pt surface, leading to Pt site deactivation. To address this challenge, we published a series of works in terms of poisoning mechanisms, regeneration protocols, and advanced poisoning-tolerant catalysts. Herein, we are aiming at developing a SO₂-tolerant electrocatalyst toward a cathodic oxygen reduction reaction (ORR). We reasonably incorporate the Ru, synthesize Ru@Pt core@shell catalysts and investigate the relationships among Ru incorporation, ORR activity and SO₂ tolerance. Impressively, the Ru@Pt/C exhibits higher initial ORR activity (0.288 A mg⁻¹_Pt), better SO₂ poisoning resistance (33% loss in initial activity) than that of commercial Pt/C catalysts (0.252 A mg⁻¹_Pt; 62% loss). The engineered affinity between Pt and SO₂ in the presence of Ru is uncovered to account for the improvement. Full article

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

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33 pages, 3151 KiB

Open AccessReview

Modified Zeolites for the Removal of Emerging Bio-Resistive Pollutants in Water Resources

by Fatin Samara, Amer A. Al Abdel Hamid, Venkatesh Gopal, Lara Dronjak, Fares Feghaly and Sofian Kanan

Catalysts 2025, 15(2), 138; https://doi.org/10.3390/catal15020138 - 2 Feb 2025

Abstract

The increasing presence of pollutants, including pharmaceuticals and pesticides, in water resources necessitates the development of effective remediation technologies. Zeolites are promising agents for pollutant removal due to their high surface area, ion-exchange capacity, natural abundance, and diverse tailorable porous structures. This review [...] Read more.

The increasing presence of pollutants, including pharmaceuticals and pesticides, in water resources necessitates the development of effective remediation technologies. Zeolites are promising agents for pollutant removal due to their high surface area, ion-exchange capacity, natural abundance, and diverse tailorable porous structures. This review focuses on the efficient application of modified zeolites and mesoporous materials as photocatalysts and adsorbents for removing contaminants from water bodies. The adsorption and photodegradation of pesticides and selected non-steroidal anti-inflammatory drugs and antibiotics on various zeolites reveal optimal adsorption and degradation conditions for each pollutant. In most reported studies, higher SiO₂/Al₂O₃ ratio zeolites exhibited improved adsorption, and thus photodegradation activities, due to increased hydrophobicity and lower negative charge. For example, SBA-15 demonstrated high efficiency in removing diclofenac, ibuprofen, and ketoprofen from water in acidic conditions. Metal doped into the zeolite framework was found to be a very active catalyst for the photodegradation of organic pollutants, including pesticides, pharmaceuticals, and industrial wastes. It is shown that the photocatalytic activity depends on the zeolite-type, metal dopant, metal content, zeolite pore structure, and the energy of the irradiation source. Faujasite-type Y zeolites combined with ozone achieved up to 95% micropollutant degradation. Bentonite modified with cellulosic biopolymers effectively removed pesticides such as atrazine and chlorpyrifos, while titanium and/or silver-doped zeolites showed strong catalytic activity in degrading carbamates, highlighting their environmental application potential. Full article

(This article belongs to the Special Issue Recent Advances in Photocatalytic Treatment of Pollutants in Water)

50 pages, 3534 KiB

Open AccessReview

Substrate Engineering of Single Atom Catalysts Enabled Next-Generation Electrocatalysis to Power a More Sustainable Future

by Saira Ajmal, Junfeng Huang, Jianwen Guo, Mohammad Tabish, Muhammad Asim Mushtaq, Mohammed Mujahid Alam and Ghulam Yasin

Catalysts 2025, 15(2), 137; https://doi.org/10.3390/catal15020137 - 1 Feb 2025

Abstract

Single-atom catalysts (SACs) are presently recognized as cutting-edge heterogeneous catalysts for electrochemical applications because of their nearly 100% utilization of active metal atoms and having well-defined active sites. In this regard, SACs are considered renowned electrocatalysts for electrocatalytic O₂ reduction reaction (ORR), [...] Read more.

Single-atom catalysts (SACs) are presently recognized as cutting-edge heterogeneous catalysts for electrochemical applications because of their nearly 100% utilization of active metal atoms and having well-defined active sites. In this regard, SACs are considered renowned electrocatalysts for electrocatalytic O₂ reduction reaction (ORR), O₂ evolution reaction (OER), H₂ evolution reaction (HER), water splitting, CO₂ reduction reaction (CO₂RR), N₂ reduction reaction (NRR), and NO₃ reduction reaction (NO₃RR). Extensive research has been carried out to strategically design and produce affordable, efficient, and durable SACs for electrocatalysis. Meanwhile, persistent efforts have been conducted to acquire insights into the structural and electronic properties of SACs when stabilized on an adequate matrix for electrocatalytic reactions. We present a thorough and evaluative review that begins with a comprehensive analysis of the various substrates, such as carbon substrate, metal oxide substrate, alloy-based substrate, transition metal dichalcogenides (TMD)-based substrate, MXenes substrate, and MOF substrate, along with their metal-support interaction (MSI), stabilization, and coordination environment (CE), highlighting the notable contribution of support, which influences their electrocatalytic performance. We discuss a variety of synthetic methods, including bottom-up strategies like impregnation, pyrolysis, ion exchange, atomic layer deposition (ALD), and electrochemical deposition, as well as top-down strategies like host-guest, atom trapping, ball milling, chemical vapor deposition (CVD), and abrasion. We also discuss how diverse regulatory strategies, including morphology and vacancy engineering, heteroatom doping, facet engineering, and crystallinity management, affect various electrocatalytic reactions in these supports. Lastly, the pivotal obstacles and opportunities in using SACs for electrocatalytic processes, along with fundamental principles for developing fascinating SACs with outstanding reactivity, selectivity, and stability, have been highlighted. Full article

(This article belongs to the Special Issue Feature Review Papers in Electrocatalysis)

13 pages, 3457 KiB

Open AccessArticle

Regulation of Ni₃S₂@NiS Heterostructure Grown on Industrial Nickel Net for Improved Electrocatalytic Hydrogen Evolution

by Zihan Su, Dinghan Liu, Yuhang Li, Xiaoyi Li, Dewei Chu, Liyun Cao, Jianfeng Huang and Liangliang Feng

Catalysts 2025, 15(2), 136; https://doi.org/10.3390/catal15020136 - 1 Feb 2025

Abstract

A novel all-in-one catalytic electrode containing a Ni₃S₂@NiS heterostructure (Ni₃S₂@NiS/Ni-Net) was in situ synthesized on an industrial nickel net (Ni-Net) using a one-step solvothermal method, in which ethanol was the solvent and thioacetamide was the [...] Read more.

A novel all-in-one catalytic electrode containing a Ni₃S₂@NiS heterostructure (Ni₃S₂@NiS/Ni-Net) was in situ synthesized on an industrial nickel net (Ni-Net) using a one-step solvothermal method, in which ethanol was the solvent and thioacetamide was the sulfur source, respectively. The effects of the addition amount of the sulfur source on the composition, morphology, and electronic structure of the Ni₃S₂@NiS heterostructures and their electrocatalytic hydrogen evolution reaction (HER) activities were investigated. When 2 mmol of sulfur source was introduced, the prepared Ni₃S₂@NiS/Ni-Net electrode with a nanorod-like structure required overpotentials of 207 and 322 mV to drive the current densities of 100 and 500 mA/cm², respectively, in 1 M KOH solution, and only needed the overpotential of 429 mV to deliver 1000 mA/cm². Meanwhile, the Ni₃S₂@NiS/Ni-Net electrode can operate stably at a high current density of 90 mA/cm² under harsh alkaline conditions for at least 100 h. The results show that the Ni₃S₂@NiS/Ni-Net electrode has high activity and stable HER performance at a high current density, which provides a new idea for the development of high-efficiency electrodes for industrial alkaline hydrogen production. Full article

(This article belongs to the Special Issue Tailored Nanosystems and Nanocatalysts for Photo-/Electrocatalytic Applications, 2nd Edition)

19 pages, 2477 KiB

Open AccessFeature PaperReview

Inorganic Bismuth Catalysts for Photocatalytic Organic Reactions

by Hualei He, Qiyan Lv and Bing Yu

Catalysts 2025, 15(2), 135; https://doi.org/10.3390/catal15020135 - 1 Feb 2025

Abstract

Bismuth (Bi) is recognized as a low-toxicity and environmentally friendly metal. Owing to its diverse oxidation states, Bi-based compounds demonstrate exceptional catalytic activities across numerous organic reactions. In particular, Bi-based inorganic materials have emerged as a promising class of photocatalysts in synthetic chemistry. [...] Read more.

Bismuth (Bi) is recognized as a low-toxicity and environmentally friendly metal. Owing to its diverse oxidation states, Bi-based compounds demonstrate exceptional catalytic activities across numerous organic reactions. In particular, Bi-based inorganic materials have emerged as a promising class of photocatalysts in synthetic chemistry. In this review, the recent applications of inorganic Bi-materials, e.g., Bi₂O₃, BiVO₄, BiCl₃, Bi₂WO₆, and Bi₄O₅Br₂, as photocatalysts in various organic reactions, including C-H oxidation, radical addition of olefins, and coupling reactions, have been summarized. The reaction mechanisms are discussed to reveal the crucial steps for enhancing catalytic performance. Moreover, the current challenges and prospects in this vibrant research area are also outlined, aiming to provide valuable insights and guidance for the development of more efficient Bi-based photocatalysts and their applications in diverse organic synthetic pathways. Full article

(This article belongs to the Special Issue Photocatalysis: Past, Present, and Future Outlook)

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44 pages, 1554 KiB

Open AccessReview

Oxides and Metal Oxide/Carbon Hybrid Materials for Efficient Photocatalytic Organic Pollutant Removal

by Abu Saad Ansari, Griszha Azzahra, Fairuz Gianirfan Nugroho, Momin M. Mujtaba and Abu Talha Aqueel Ahmed

Catalysts 2025, 15(2), 134; https://doi.org/10.3390/catal15020134 - 1 Feb 2025

Abstract

Pharmaceuticals are increasingly significant contaminants in the environmental ecosystem, prompting the exploration of photocatalysis as a promising method for removing their pollutants. However, the application of semiconductor metal oxides as photocatalysts has been limited by issues such as rapid photocarrier recombination and high [...] Read more.

Pharmaceuticals are increasingly significant contaminants in the environmental ecosystem, prompting the exploration of photocatalysis as a promising method for removing their pollutants. However, the application of semiconductor metal oxides as photocatalysts has been limited by issues such as rapid photocarrier recombination and high band gap energy. One emerging strategy to enhance the photocatalytic performance of metal oxides involves integrating them with carbon dots, which offer advantages including low toxicity, aqueous stability, increased surface area, cost effectiveness, biocompatibility, and chemical inertness. In this study, we conducted a critical review focusing on the nanocomposite development of metal oxide/carbon dots for the photocatalytic removal of pharmaceutical pollutants. Our study highlights that carbon dots can significantly enhance the photocatalytic efficiency of these metal oxides as photocatalytic materials by improving the adsorption of organic pollutants and enhancing light absorption in the visible spectrum. This review aims to provide insights for future research aimed at advancing the development of enhanced photocatalytic metal oxide/carbon dot nanocomposites. Full article

(This article belongs to the Special Issue Latest Advances and Prospects of Nanomaterials for Catalysis and Energy Storage)

16 pages, 2932 KiB

Open AccessArticle

Waste for Product: Pd and Pt Nanoparticle-Modified Ni Foam as a Universal Catalyst for Hydrogen/Oxygen Evolution Reaction and Methyl Orange Degradation

by Julia Druciarek, Dawid Kutyła, Adrianna Pach, Anna Kula and Magdalena Luty-Błocho

Catalysts 2025, 15(2), 133; https://doi.org/10.3390/catal15020133 - 30 Jan 2025

Abstract

Declining natural resources make the recovery of metals from waste solutions a promising alternative. Moreover, processing waste into a finished product has its economic justification and benefits. Thus, the aim of this research was developing a Waste for Product strategy, indicating the possibility [...] Read more.

Declining natural resources make the recovery of metals from waste solutions a promising alternative. Moreover, processing waste into a finished product has its economic justification and benefits. Thus, the aim of this research was developing a Waste for Product strategy, indicating the possibility of processing solutions with a low content of platinum-group metals for catalyst synthesis. The results obtained confirmed that diluted synthetic waste solutions containing trace amount of valuable metal ions (Pd, Pt) can be used for the process of catalyst synthesis. Catalysts produced in the form of palladium and platinum nanoparticles were successfully deposited on a Ni foam due to the galvanic displacement mechanism. Synthesized catalysts were characterized using UV-Vis spectrophotometry, SEM/EDS, and XRD techniques. Electro- and catalytic properties were tested for hydrogen/oxygen evolution reactions and methyl orange degradation, respectively. The results obtained from electrocatalytic tests indicated that the modification of the nickel foam surface by waste solutions consisting of noble metals ions as Pd and Pt can significantly increase the activity in hydrogen and oxygen evolution reactions in comparison to non-treated samples. Catalytic tests performed for the process of methyl orange degradation shorten the time of the process from several hours to 15 min. The most favorable results were obtained for the catalysts in the following order Pd1.0Pt0@Ni > Pd0Pt1.0@Ni > Pd0.5Pt0.5@Ni > Ni foam > no catalyst, indicating the best catalytic performance for catalyst containing pure palladium nanoparticles deposited on the nickel surface. Full article

(This article belongs to the Special Issue Commemorative Special Issue for Prof. Dr. Dion Dionysiou)

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16 pages, 5450 KiB

Open AccessArticle

A Unique Dual-Shell Structure with Highly Active Ni@SiC/CNT/CNF Microwave Catalysts

by Xizong Liu, Yulei Zhang, Heng Wu, Dongsheng Zhang, Jiaqi Liu and Haibo Ouyang

Catalysts 2025, 15(2), 132; https://doi.org/10.3390/catal15020132 - 30 Jan 2025

Abstract

Microwave-assisted catalytic oxidation (MACO) is a novel wastewater treatment technology for the efficient treatment degradation of organic wastewater. However, a single carbon material or SiC has limited absorption of electromagnetic waves, and the efficiency of using it as a microwave-assisted organic catalyst is [...] Read more.

Microwave-assisted catalytic oxidation (MACO) is a novel wastewater treatment technology for the efficient treatment degradation of organic wastewater. However, a single carbon material or SiC has limited absorption of electromagnetic waves, and the efficiency of using it as a microwave-assisted organic catalyst is not satisfactory. To improve the absorption and microwave-assisted degradation performance of carbon matrix composites, a new carbon magnetic composite Ni@SiC/CNT/CNF microwave catalyst is constructed. By controlling the introduction of nickel, different numbers of carbon nanotubes are grown on the surface of carbon nanofibers, and C and SiC double-shell structures were formed on the top of the carbon nanotubes, which catalyzed the generation of active groups by the thermal effect generated by the plasma discharge under the action of microwave field, thus realizing the highly efficient catalytic degradation of wastewater dyes. The results show that the Ni@SiC/CNT/CNF with the lowest reflection loss of RL_min = −9.26 dB exhibit excellent degradation capabilities with a degradation efficiency of 99.9% for methylene blue within 90 s under 450 W microwave irradiation. Full article

(This article belongs to the Special Issue Tailored Nanosystems and Nanocatalysts for Photo-/Electrocatalytic Applications, 2nd Edition)

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19 pages, 3646 KiB

Open AccessArticle

Effect of Sm₂O₃ Doping of CeO₂-Supported Ni Catalysts for H₂ Production by Steam Reforming of Ethanol

by Carlos Andrés Chirinos, Sichen Liu, Vicente Cortés Corberán and Luisa María Gómez-Sainero

Catalysts 2025, 15(2), 131; https://doi.org/10.3390/catal15020131 - 29 Jan 2025

Abstract

Hydrogen is a priority energy vector for energy transition. Its production from renewable feedstock like ethanol is suitable for many applications. The performance of a Ni catalyst supported on samaria-doped ceria in the production of hydrogen by the reforming of ethanol is investigated, [...] Read more.

Hydrogen is a priority energy vector for energy transition. Its production from renewable feedstock like ethanol is suitable for many applications. The performance of a Ni catalyst supported on samaria-doped ceria in the production of hydrogen by the reforming of ethanol is investigated, adding Sm₂O₃ to CeO₂ in molar ratios of 1:9, 2:8, and 3:7. A CeO₂-supported Ni catalyst was also evaluated for comparative purposes. The supports were prepared by the coprecipitation method and Ni was incorporated by incipient wetness impregnation to obtain catalysts with a Ni/(Ce+Sm) molar ratio of 4/6. The catalysts were characterized by a nitrogen adsorption isotherm, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Increasing Sm₂O₃ content leads to a more homogeneous distribution of Sm₂O₃and Ni particles on the support, and higher oxygen mobility, favoring the catalytic properties. The catalyst with a Sm₂O₃/CeO₂ molar ratio of 3/7 showed outstanding behavior, with an average ethanol conversion of 97%, hydrogen yield of 68%, and great stability. The results suggest that the main route for hydrogen production is ethanol dehydrogenation, followed by steam reforming of acetaldehyde, and acetone and ethylene formation are promoted by increasing Sm content in the outer surface of the catalyst. Full article

(This article belongs to the Special Issue Catalysis for Hydrogen Storage and Release)

21 pages, 4270 KiB

Open AccessArticle

Electrocatalytic Pathways and Efficiency of Cuprous Oxide (Cu₂O) Surfaces in CO₂ Electrochemical Reduction (CO₂ER) to Methanol: A Computational Approach

by Zubair Ahmed Laghari, Wan Zaireen Nisa Yahya, Sulafa Abdalmageed Saadaldeen Mohammed and Mohamad Azmi Bustam

Catalysts 2025, 15(2), 130; https://doi.org/10.3390/catal15020130 - 29 Jan 2025

Abstract

Carbon dioxide (CO₂) can be electrochemically, thermally, and photochemically reduced into valuable products such as carbon monoxide (CO), formic acid (HCOOH), methane (CH₄), and methanol (CH₃OH), contributing to carbon footprint mitigation. Extensive research has focused on catalysts, [...] Read more.

Carbon dioxide (CO₂) can be electrochemically, thermally, and photochemically reduced into valuable products such as carbon monoxide (CO), formic acid (HCOOH), methane (CH₄), and methanol (CH₃OH), contributing to carbon footprint mitigation. Extensive research has focused on catalysts, combining experimental approaches with computational quantum mechanics to elucidate reaction mechanisms. Although computational studies face challenges due to a lack of accurate approximations, they offer valuable insights and assist in selecting suitable catalysts for specific applications. This study investigates the electrocatalytic pathways of CO₂reduction on cuprous oxide (Cu₂O) catalysts, utilizing the computational hydrogen electrode (CHE) model based on density functional theory (DFT). The electrocatalytic performance of flat Cu₂O (100) and hexagonal Cu₂O (111) surfaces was systematically analysed, using the standard hydrogen electrode (SHE) as a reference. Key parameters, including free energy changes (ΔG), adsorption energies (E_ads), reaction mechanisms, and pathways for various intermediates were estimated. The results showed that CO₂ was reduced to CO_(g) on both Cu₂O surfaces at low energies. However, methanol (CH₃OH) production was observed preferentially on Cu₂O (111) at ΔG = −1.61 eV, whereas formic acid (HCOOH) and formaldehyde (HCOH) formation were thermodynamically unfavourable at interfacial sites. The CO₂-to-methanol conversion on Cu₂O (100) exhibited a total ΔG of −3.38 eV, indicating lower feasibility compared to Cu₂O (111) with ΔG = −5.51 eV. These findings, which are entirely based on a computational approach, highlight the superior catalytic efficiency of Cu₂O (111) for methanol synthesis. This approach also holds the potential for assessing the catalytic performance of other transition metal oxides (e.g., nickel oxide, cobalt oxide, zinc oxide, and molybdenum oxide) and their modified forms through doping or alloying with various elements. Full article

(This article belongs to the Special Issue Catalysis for CO₂ Conversion, 2nd Edition)

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11 pages, 2637 KiB

Open AccessCommunication

Depolymerization of PET with n-Hexylamine, n-Octylamine, and 3-Amino-1-Propanol, Affording Terephthalamides

by Sumiho Hiruba, Yohei Ogiwara and Kotohiro Nomura

Catalysts 2025, 15(2), 129; https://doi.org/10.3390/catal15020129 - 29 Jan 2025

Abstract

The chemical conversion of plastic waste has been considered an important subject in terms of the circular economy, and the chemical recycling and upcycling of poly(ethylene terephthalate) (PET) has been considered one of the most important subjects. In this study, the depolymerization of [...] Read more.

The chemical conversion of plastic waste has been considered an important subject in terms of the circular economy, and the chemical recycling and upcycling of poly(ethylene terephthalate) (PET) has been considered one of the most important subjects. In this study, the depolymerization of PET with n-hexylamine, n-octylamine, and 3-amino-1-propanol has been explored in the presence of Cp*TiCl₃ (Cp* = C₅Me₅). The reactions of PET with n-hexylamine and n-octylamine at 130 °C afforded the corresponding N,N′-di(n-alkyl) terephthalamides in high yields (>90%), and Cp*TiCl₃ plays a role as the catalyst to facilitate the conversion in exclusive selectivity. The reaction of PET with 3-amino-1-propanol proceeded at 100 °C even in the absence of the Ti catalyst, affording N,N′-bis(3-hydroxy) terephthalamides in high yields. A unique contrast has been demonstrated between the depolymerization of PET by transesterification with alcohol and by aminolysis; the depolymerizations with these amines proceeded without the aid of a catalyst. Full article

(This article belongs to the Special Issue State-of-the-Art Polymerization Catalysis)

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13 pages, 1344 KiB

Open AccessArticle

Methanol-Tolerant Pd-Co Alloy Nanoparticles on Reduced Graphene Oxide as Cathode Catalyst for Oxygen Reduction in Fuel Cells

by Chandra Sekhar Yellatur, Venkatachalam Vinothkumar, Poshan Kumar Reddy Kuppam, Juwon Oh and Tae Hyun Kim

Catalysts 2025, 15(2), 128; https://doi.org/10.3390/catal15020128 - 29 Jan 2025

Abstract

The design of efficient and cost-effective electrocatalysts to replace Pt in an oxygen reduction reaction (ORR) is crucial for advancing proton exchange membrane fuel cell (PEMFC) technologies. This study synthesized Pd-Co bimetallic alloy nanoparticles supported on reduced graphene oxide (rGO) through a simple [...] Read more.

The design of efficient and cost-effective electrocatalysts to replace Pt in an oxygen reduction reaction (ORR) is crucial for advancing proton exchange membrane fuel cell (PEMFC) technologies. This study synthesized Pd-Co bimetallic alloy nanoparticles supported on reduced graphene oxide (rGO) through a simple chemical-reduction method, making it suitable for low-cost, large-scale fabrication and significantly reducing the need for Pt. The nanostructures were systematically characterized using various analytical techniques, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). Electrochemical investigations revealed that the Pd-Co/rGO catalyst exhibits remarkable ORR performance in an alkaline environment, with an electrode-area-normalized activity rivaling that of the commercial Pt/C catalyst. Remarkably, Pd-Co/rGO demonstrated an onset potential (E_onset) of 0.944 V (vs. RHE) and a half-wave potential (E_1/2) of 0.782 V (vs. RHE), highlighting its excellent ORR activity. Furthermore, the Pd-Co/rGO catalyst displayed superior methanol-tolerant ORR activity, outperforming Pt/C and monometallic Pd/rGO and Co/rGO systems. The enhanced electrocatalytic performance is attributed to the smallest size, consistent shape, and good dispersion of the alloy structure on the RGO surface. These findings establish Pd-Co/rGO as a promising alternative to Pt-based catalysts, addressing key challenges such as methanol crossover while advancing PEMFC technology in alkaline media. Full article

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

19 pages, 666 KiB

Open AccessReview

A Comprehensive Review on Barrelene-Derived α-Diimine Nickel and Palladium Olefin Polymerization Catalysts

by Haotian Zhou, Chunyu Feng, Handou Zheng, Guangshui Tu, Xieyi Xiao and Haiyang Gao

Catalysts 2025, 15(2), 127; https://doi.org/10.3390/catal15020127 - 28 Jan 2025

Abstract

Late transition metal olefin polymerization catalysts have received more attention in the field of catalytic olefin polymerization. Barrelene-based α-diimine nickel and palladium olefin polymerization catalysts are rising stars because of their backbone structure and catalytic properties. In this review, we present a comprehensive [...] Read more.

Late transition metal olefin polymerization catalysts have received more attention in the field of catalytic olefin polymerization. Barrelene-based α-diimine nickel and palladium olefin polymerization catalysts are rising stars because of their backbone structure and catalytic properties. In this review, we present a comprehensive review of barrelene-derived α-diimine nickel and palladium olefin polymerization catalysts. α-Diimine nickel and palladium catalysts are introduced from two aspects: barrelene-derived backbone and aniline derivatives with different substituents. The relationship between catalyst structure and catalytic properties is also emphasized. This review attempts to provide an inspiration for the design of high-performance barrelene-based catalysts. Full article

(This article belongs to the Special Issue State-of-the-Art Polymerization Catalysis)

17 pages, 3856 KiB

Open AccessArticle

Piezoelectric-Driven Fenton System Based on Bismuth Ferrite Nanosheets for Removal of N-acetyl-para-aminophenol in Aqueous Environments

by Chi Zhou, Shenglong Jing, Teng Miao, Nianlai Zhou, Hang Zhang, Yi Zhang, Lin Ge, Wencheng Liu and Zixin Yang

Catalysts 2025, 15(2), 126; https://doi.org/10.3390/catal15020126 - 27 Jan 2025

Abstract

Emerging pollutants, such as N-acetyl-para-aminophenol, pose significant challenges to environmental sustainability, and Bi₂Fe₂O₂ (BFO) nanomaterials are an emerging class of piezoelectric materials. This study presents a novel piezoelectric-driven Fenton system based on Bi₂Fe₄O [...] Read more.

Emerging pollutants, such as N-acetyl-para-aminophenol, pose significant challenges to environmental sustainability, and Bi₂Fe₂O₂ (BFO) nanomaterials are an emerging class of piezoelectric materials. This study presents a novel piezoelectric-driven Fenton system based on Bi₂Fe₄O₉ nanosheets for the efficient degradation of organic pollutants. BFO nanosheets with varying thicknesses were synthesized, and their piezoelectric properties were confirmed through piezoresponse force microscopy and heavy metal ion reduction experiments. The piezoelectric electrons generated within the BFO nanosheets facilitate the in situ production of hydrogen peroxide, which in turn drives the Fenton-like reaction. Furthermore, the piezoelectric electrons enhance the redox cycling of iron in the Fenton process, boosting the overall catalytic efficiency. The energy band structure of BFO nanosheets is well-suited for this process, enabling efficient hydrogen peroxide generation and promoting Fe³⁺ reduction. The findings demonstrate that thinner BFO nanosheets exhibit superior piezoelectric activity, leading to enhanced catalytic performance. Additionally, the incorporation of gold nanodots onto BFO nanosheets further boosts their piezocatalytic efficiency, particularly in the reduction of Cr (VI). The system exhibited robust oxidative capacity, stability, and recyclability, with reactive oxygen species (ROS) verified via electron paramagnetic resonance spectroscopy. Overall, BFO nanosheets, with their optimal energy band structure, self-supplied hydrogen peroxide, and enhanced Fe³⁺ reduction, represent a promising, sustainable solution for advanced oxidation processes in wastewater treatment and other applications. Full article

(This article belongs to the Special Issue Sustainable Catalysis for Green Chemistry and Energy Transition)

17 pages, 1528 KiB

Open AccessArticle

Innovative Production of 3D-Printed Ceramic Monolithic Catalysts for Oxidation of VOCs by Using Fused Filament Fabrication

by Filip Car, Nikolina Zekić, Domagoj Vrsaljko and Vesna Tomašić

Catalysts 2025, 15(2), 125; https://doi.org/10.3390/catal15020125 - 27 Jan 2025

Abstract

In this work, ceramic monolithic catalyst carriers based on zirconium dioxide (ZrO₂) were produced using fused filament fabrication (FFF). The active catalyst components were deposited on the resulting carriers using the wet impregnation method. The activity of the prepared monolithic catalysts [...] Read more.

In this work, ceramic monolithic catalyst carriers based on zirconium dioxide (ZrO₂) were produced using fused filament fabrication (FFF). The active catalyst components were deposited on the resulting carriers using the wet impregnation method. The activity of the prepared monolithic catalysts was evaluated by catalytic oxidation of a mixture of aromatic volatile organic compounds: benzene, toluene, ethylbenzene, and o-xylene (BTEX). The efficiency of the prepared monolithic catalysts was investigated as a function of the geometry of the monolithic carrier (ZDP, Z, and M) and the chemical composition of the catalytically active component (MnFeO_x, MnCuO_x, and MnNiO_x) during the catalytic oxidation of BTEX compounds. The mechanical stability of the catalyst layer and the dimensional stability of the 3D-printed monolithic catalyst carriers were investigated prior to the kinetic measurements. In addition, thorough characterization of the commercial ZrO₂-based filament was carried out. The results of the efficiency of the prepared monolithic catalysts for the catalytic oxidation of BTEX showed that the 3D-printed model M, which contained MnFeO_x as the catalytically active component, was the most successful catalyst for the oxidation of BTEX compounds. The mentioned catalyst enables the catalytic oxidation of all components of the BTEX mixture (>99% efficiency) at a temperature of 177 °C. Full article

(This article belongs to the Special Issue Advances in Catalysis for a Sustainable Future)

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36 pages, 7819 KiB

Open AccessReview

Recent Advances in Transition Metal Chalcogenides Electrocatalysts for Oxygen Evolution Reaction in Water Splitting

by Honglin Gao, Ting Yang, Aiyi Dong, Yuliang Xing, Dajun Liu, Yinhua Ma and Kaixin Zhu

Catalysts 2025, 15(2), 124; https://doi.org/10.3390/catal15020124 - 27 Jan 2025

Abstract

Rapid industrial growth has overexploited fossil fuels, making hydrogen energy a crucial research area for its high energy and zero carbon emissions. Water electrolysis is a promising method as it is greenhouse gas-free and energy-efficient. However, OER, a slow multi-electron transfer process, is [...] Read more.

Rapid industrial growth has overexploited fossil fuels, making hydrogen energy a crucial research area for its high energy and zero carbon emissions. Water electrolysis is a promising method as it is greenhouse gas-free and energy-efficient. However, OER, a slow multi-electron transfer process, is the limiting step. Thus, developing efficient, low-cost, abundant electrocatalysts is vital for large-scale water electrolysis. In this paper, the application and progress of transition metal chalcogenides (TMCs) as catalysts for the oxygen evolution reaction in recent years are comprehensively reviewed. The key findings highlight the catalytic mechanism and performance of TMCs synthesized using single or multiple transition metals. Notably, modifications through recombination, heterogeneous interface engineering, vacancy, and atom doping are found to effectively regulate the electronic structure of metal chalcogenides, increasing the number of active centers and reducing the adsorption energy of reaction intermediates and energy barriers in OER. The paper further discusses the shortcomings and challenges of TMCs as OER catalysts, including low electrical conductivity, limited active sites, and insufficient stability under harsh conditions. Finally, potential research directions for developing new TMC catalysts with enhanced efficiency and stability are proposed. Full article

(This article belongs to the Special Issue Recent Advances in Electrocatalysis and Future Perspective)

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20 pages, 6117 KiB

Open AccessArticle

Sustainable Synthesis of Zirconium Dioxide (ZrO₂) Nanoparticles Utilizing Asphodelus fistulosus Extract for Congo Red Degradation

by Rand A. N. Alkhalifa, Abuzar E. A. E. Albadri, Reham Ali, Abdullah H. Alluhayb, Alaa M. Younis and Sayed M. Saleh

Catalysts 2025, 15(2), 123; https://doi.org/10.3390/catal15020123 - 27 Jan 2025

Abstract

This research presents a green approach to synthesizing zirconium oxide (ZrO₂) nanoparticles using an Asphodelus fistulosus plant extract as a reducing and stabilizing agent. The synthesized ZrO₂ nanoparticles were characterized using various advanced techniques. The XRD pattern provides different forms [...] Read more.

This research presents a green approach to synthesizing zirconium oxide (ZrO₂) nanoparticles using an Asphodelus fistulosus plant extract as a reducing and stabilizing agent. The synthesized ZrO₂ nanoparticles were characterized using various advanced techniques. The XRD pattern provides different forms of ZrO₂, like tetragonal and cubic forms, and the results confirmed the successful formation of crystalline ZrO₂ nanoparticles with a definite morphology. The XPS data exhibit that the bioactive chemicals present in the extract, including polyphenols, flavonoids, and reducing sugars, perform the functions of reducing and capping agents. Additionally, CR dye molecules may create hydrogen bonds with these surface moieties, which are approved by FTIR. These interactions may assist in aligning dye molecules with catalytically active regions on ZrO₂ surfaces and may interact with photogenerated species. The catalytic activity of the synthesized ZrO₂ nanoparticles was evaluated for the degradation of Congo red dye under ultraviolet irradiation. The nanoparticles exhibited excellent photocatalytic activity, degrading a significant amount of the dye within a short period. Various parameters were investigated to optimize the photodegradation process, including irradiation time, catalyst dosage, pH, and initial dye concentration. The optimal conditions were determined to be a pH of 7, a catalyst loading of 20 mg/L, and an irradiation time of 75 min, resulting in a remarkable ≈92% degradation efficiency. This green synthesis method offers a sustainable and eco-friendly alternative to conventional chemical methods for producing ZrO₂ nanoparticles, which have potential applications in environmental remediation. Full article

(This article belongs to the Special Issue Nanocatalysts in Energy and Environmental Applications)

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17 pages, 4619 KiB

Open AccessArticle

Alumina Coated with Titanium Dioxide Supported Iron for Hydrogen Production and Carbon Nanotubes via Methane Decomposition

by Hamid Ahmed, Anis H. Fakeeha, Fayez M. Al-Alweet, Syed Farooq Adil, Ahmed E. Abasaeed, Ahmed A. Ibrahim, Ahmed I. Osman, Salwa B. Alreshaidan and Ahmed S. Al-Fatesh

Catalysts 2025, 15(2), 122; https://doi.org/10.3390/catal15020122 - 27 Jan 2025

Abstract

Research on converting methane to hydrogen has gained more attention due to the availability of methane reserves and the global focus on sustainable and environmentally friendly energy sources. The decomposition of methane through catalysis (CDM) has excellent potential to produce clean hydrogen and [...] Read more.

Research on converting methane to hydrogen has gained more attention due to the availability of methane reserves and the global focus on sustainable and environmentally friendly energy sources. The decomposition of methane through catalysis (CDM) has excellent potential to produce clean hydrogen and valuable carbon products. However, developing catalysts that are both active and stable is a highly challenging area of research. Using titanium isopropoxide as a precursor and different loadings of TiO₂ (10 wt.%, 20 wt.%, and 30 wt.%), alumina has been coated with TiO₂ in a single-step hydrothermal synthesis procedure. These synthesized materials are examined as possible support materials for CDM; different wt.% of iron is loaded onto the synthesized support material using a co-precipitation method to enhance the methane conversion via a decomposition reaction. The result shows that the 20 wt.% Fe/20 wt.% Ti-Al (20Fe/20Ti-Al) catalyst demonstrates remarkable stability and exhibits superior performance, reaching a conversion rate of methane of 94% with hydrogen production of 84% after 4 h. The outstanding performance is primarily due to the moderate interaction between the support and the active metal, as well as the presence of the rutile phase. The 20Fe/30Ti-Al catalyst exhibited lower activity than the other catalysts, achieving a methane conversion of 85% and hydrogen production of 79% during the reaction. Raman and XRD analysis revealed that all the catalysts generated graphitic carbon, with the 20Fe/20Ti-Al catalyst specifically producing single-walled carbon nanotubes. Full article

(This article belongs to the Section Industrial Catalysis)

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