Catalysts

12 pages, 6066 KiB

Open AccessEditor’s ChoiceArticle

Metal Bi Loaded Bi₂Ti₂O₇/CaTiO₃ for Enhanced Photocatalytic Efficiency for NO Removal under Visible Light

by Diyuan Du, Menglin Shi, Qingqing Guo, Yanqin Zhang, Ahmed A. Allam, Ahmed Rady and Chuanyi Wang

Catalysts 2023, 13(8), 1169; https://doi.org/10.3390/catal13081169 - 30 Jul 2023

Cited by 4 | Viewed by 1383

Abstract

NO has caused many serious environmental problems and even seriously threatened human health. The development of a cheap and efficient method to remove NO from the air has become an urgent need. In this paper, a novel nanocomposite metal-semiconductor photocatalyst Bi-Bi₂Ti [...] Read more.

NO has caused many serious environmental problems and even seriously threatened human health. The development of a cheap and efficient method to remove NO from the air has become an urgent need. In this paper, a novel nanocomposite metal-semiconductor photocatalyst Bi-Bi₂Ti₂O₇/CaTiO₃ was prepared. Compared to the original Bi₂Ti₂O₇/CaTiO₃, the modification by the metal Bi increased its photocatalytic activity from 25% to 64% under visible light irradiation. The improved photoactivity owns to the SPR effect and the electron capture effect of Bi metals in metal-semiconductor loaded systems improving the separation efficiency of electron-hole pairs and significantly improving the light absorption capacity of the composite photocatalyst. The capture experiment of active species showed that •OH, •O₂⁻, h⁺ and e⁻ are the main active species in the photocatalytic conversion of NO. This work provides new insights into the conformational relationships of Ti-based photocatalysts for NO removal. Full article

(This article belongs to the Special Issue Photocatalysis in Air Purification)

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18 pages, 5117 KiB

Open AccessEditor’s ChoiceArticle

Photocatalytic Systems Based on ZnO Produced by Supercritical Antisolvent for Ceftriaxone Degradation

by Stefania Mottola, Antonietta Mancuso, Olga Sacco, Vincenzo Vaiano and Iolanda De Marco

Catalysts 2023, 13(8), 1173; https://doi.org/10.3390/catal13081173 - 30 Jul 2023

Cited by 6 | Viewed by 1572

Abstract

Emerging contaminants are a significant issue in the environment. Photocatalysis is proposed as a solution for the degradation of pollutants contained in wastewater. In this work, ZnO-based photocatalysts have been produced and tested for the photocatalytic degradation of an antibiotic; specifically, ceftriaxone has [...] Read more.

Emerging contaminants are a significant issue in the environment. Photocatalysis is proposed as a solution for the degradation of pollutants contained in wastewater. In this work, ZnO-based photocatalysts have been produced and tested for the photocatalytic degradation of an antibiotic; specifically, ceftriaxone has been used as a model contaminant. Moreover, there is particular interest in combining small-size ZnO particles and β-cyclodextrin (β-CD), creating a hybrid photocatalyst. Zinc acetate (ZnAc) (subsequently calcinated into ZnO) and β-CD particles with a mean diameter of 0.086 and 0.38 µm, respectively, were obtained using the supercritical antisolvent process (SAS). The produced photocatalysts include combinations of commercial and micronized particles of ZnO and β-CD and commercial and micronized ZnO. All the samples were characterized through UV–Vis diffuse reflectance spectroscopy (DRS), and the band gap values were calculated. Raman and FT-IR measurements confirmed the presence of ZnO and the existence of functional groups due to the β-cyclodextrin and ZnO combination in the hybrid photocatalysts. Wide-angle X-ray diffraction patterns proved that wurtzite is the main crystalline phase for all hybrid photocatalytic systems. In the photocatalytic degradation tests, it was observed that all the photocatalytic systems exhibited 100% removal efficiency within a few minutes. However, the commercial ZnO/micronized β-CD hybrid system is the photocatalyst that shows the best performance; in fact, when using this hybrid system, ceftriaxone was entirely degraded in 1 min. Full article

(This article belongs to the Special Issue Photocatalytical Technology in Europe: State-of-the-Art)

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21 pages, 403 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Synthesis and Specific Properties of the Ceria and Ceria-Zirconia Nanocrystals and Their Aggregates Showing Outstanding Catalytic Activity in Redox Reactions—A Review

by Roman Dziembaj, Marcin Molenda and Lucjan Chmielarz

Catalysts 2023, 13(8), 1165; https://doi.org/10.3390/catal13081165 - 29 Jul 2023

Cited by 5 | Viewed by 2180

Abstract

Non-stoichiometric CeO_2−y, especially in the form of nanocrystal aggregates, exhibits exceptional catalytic activity in redox reactions. It significantly improves the activity of transition metals and their oxides dispersed on/or in it, also acting as an oxygen buffer. Particularly, active oxygen species [...] Read more.

Non-stoichiometric CeO_2−y, especially in the form of nanocrystal aggregates, exhibits exceptional catalytic activity in redox reactions. It significantly improves the activity of transition metals and their oxides dispersed on/or in it, also acting as an oxygen buffer. Particularly, active oxygen species (O₂ⁿ⁻, O⁻) are generated at the M/CeO_2−y nanoparticle interface, as well as in the surface layer of their solid-state solutions M_xCe_1−xO_2−y. The crystal structure of CeO₂, ZrO₂ and (Ce, Zr)O₂ and its defects are discussed in connection with the resulting specific catalytic activity. All the methods (simple precipitation and co-precipitation from mother liquors, sol–gel methods, precipitation from nanoemulsions, hydrothermal and solvothermal techniques, combustion and flame spray pyrolysis, precipitation using molecular and solid-state matrices, 3D printing and mechanochemical methods) used for the synthesis of these nanomaterials are comprehensively reviewed, describing the rules of individual procedures and preparation details. Methods of deposition of metal catalysts and their oxides on CeO₂ nanoparticles, such as impregnation, washcoating and precipitation deposition, were also discussed. This review contains more than 160 references to representative papers wherein the reader can find further details on individual syntheses of effective ceria-based catalysts for redox reactions. Full article

(This article belongs to the Special Issue Nano-Porous Materials for Catalytic Systems in Green Chemistry Processes)

13 pages, 4232 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Insights into SnO₂ Nanoparticles Supported on Fibrous Mesoporous Silica for CO Catalytic Oxidation

by Guobo Li, Yingying Zhang, Jie Yan, Yiwei Luo, Conghui Wang, Weiwei Feng, Shule Zhang, Wenming Liu, Zehui Zhang and Honggen Peng

Catalysts 2023, 13(8), 1156; https://doi.org/10.3390/catal13081156 - 26 Jul 2023

Cited by 1 | Viewed by 1457

Abstract

A large surface area dendritic mesoporous silica material (KCC-1) was successfully synthesized and used as a support to confine SnO₂ nanoparticles (NPs). Owing to the large specific surface area and abundant mesoporous structure of dendritic KCC-1, the SnO₂ NPs were highly [...] Read more.

A large surface area dendritic mesoporous silica material (KCC-1) was successfully synthesized and used as a support to confine SnO₂ nanoparticles (NPs). Owing to the large specific surface area and abundant mesoporous structure of dendritic KCC-1, the SnO₂ NPs were highly dispersed, resulting in significantly improved CO catalytic oxidation activity. The obtained Sn_x/KCC-1 catalysts (x represents the mass fraction of SnO₂ loading) exhibited excellent CO catalytic activity, with the Sn₇@KCC-1 catalyst achieving 90% CO conversion at about 175 °C. The SnO₂ NPs on the KCC-1 surface in a highly dispersed amorphous form, as well as the excellent interaction between SnO₂ NPs and KCC-1, positively contributed to the catalytic removal process of CO on the catalyst surface. The CO catalytic removal pathway was established through a combination of in situ diffuse reflectance infrared transform spectroscopy and density-functional theory calculations, revealing the sequential steps: ① CO → CO₃²⁻_ads, ② CO₃²⁻_ads → CO_2free+SnO_x₋₁, ③ SnO_x₋₁+O₂ → SnO_x₊₁. This study provides valuable insights into the design of high-efficiency non-precious metal catalysts for CO catalytic oxidation catalysts with high efficiency. Full article

(This article belongs to the Special Issue Environmental Catalysis/Adsorption for Organic Waste Resource Disposal)

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15 pages, 3703 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Au Clusters Supported on Defect-Rich Ni-Ti Oxides Derived from Ultrafine Layered Double Hydroxides (LDHs) for CO Oxidation at Ambient Temperature

by Ayu Takahashi, Akihiro Nakayama, Toru Murayama, Norihito Sakaguchi, Tetsuya Shimada, Shinsuke Takagi and Tamao Ishida

Catalysts 2023, 13(8), 1155; https://doi.org/10.3390/catal13081155 - 26 Jul 2023

Viewed by 1319

Abstract

Ultrafine layered double hydroxides (LDHs) have abundant hydroxy groups at their edge sites, serving as anchor sites for metal NPs. Furthermore, transformation of ultrafine LDHs into mixed metal oxides (MMOs) generates abundant oxygen vacancies, which are advantageous for O₂ activation during Au-catalyzed [...] Read more.

Ultrafine layered double hydroxides (LDHs) have abundant hydroxy groups at their edge sites, serving as anchor sites for metal NPs. Furthermore, transformation of ultrafine LDHs into mixed metal oxides (MMOs) generates abundant oxygen vacancies, which are advantageous for O₂ activation during Au-catalyzed CO oxidation. We used ultrafine Ni-Ti LDHs with low crystallinity or Ni-Ti MMOs supported on SiO₂ onto which Au NPs were deposited by deposition–precipitation (DP) and DP–urea (DPU). The catalytic activity of the Au catalysts was significantly affected by the preparation method, with the highest activity obtained by depositing Au onto LDH/SiO₂ by DPU, followed by transformation of LDH to MMO (Au/Ni-Ti MMO/SiO₂ (LDH-DPU)). The presence of Au on LDHs affected the transformation of LDHs into MMOs, resulting in LDH-DPU having the greatest number of oxygen vacancies in the TiO₂ domain in MMOs. Consequently, the adsorbed or the lattice oxygen on the surface of LDH-DPU can be easily utilized for CO oxidation at low temperatures. Moreover, the catalytic activity of LDH-DPU increased with water vapor concentration up to 100% relative humidity at room temperature, suggesting the potential of Au/Ni-Ti MMO/SiO₂ as an air purification catalyst. Full article

(This article belongs to the Special Issue Advances in Catalytic Oxidation of Methane and Carbon Monoxide, 2nd Edition)

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15 pages, 2181 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Phosphate Coordination in a Water-Oxidizing Cobalt Oxide Electrocatalyst Revealed by X-ray Absorption Spectroscopy at the Phosphorus K-Edge

by Si Liu, Shima Farhoosh, Paul Beyer, Stefan Mebs, Michael Haumann and Holger Dau

Catalysts 2023, 13(8), 1151; https://doi.org/10.3390/catal13081151 - 25 Jul 2023

Cited by 1 | Viewed by 1813

Abstract

In the research on water splitting at neutral pH, phosphorus-containing transition metal oxyhydroxides are often employed for catalyzing the oxygen evolution reaction (OER). We investigated a cobalt–phosphate catalyst (CoCat) representing this material class. We found that CoCat films prepared with potassium phosphate release [...] Read more.

In the research on water splitting at neutral pH, phosphorus-containing transition metal oxyhydroxides are often employed for catalyzing the oxygen evolution reaction (OER). We investigated a cobalt–phosphate catalyst (CoCat) representing this material class. We found that CoCat films prepared with potassium phosphate release phosphorus in phosphate-free electrolytes within hours, contrasting orders of magnitude’s faster K⁺ release. For P speciation and binding mode characterization, we performed technically challenging X-ray absorption spectroscopy experiments at the P K-edge and analyzed the resulting XANES and EXAFS spectra. The CoCat-internal phosphorus is present in the form of phosphate ions. Most phosphate species are likely linked to cobalt ions in Co–O–PO₃ motifs, where the connecting oxygen could be a terminal or bridging ligand in Co-oxide fragments (P–Co distance, ~3.1 Å), with additional ionic bonds to K⁺ ions (P–K distance, ~3.3 Å). The phosphate coordination bond is stronger than the ionic K⁺-binding, explaining the strongly diverging ion release rates of phosphate and K⁺. Our results support a structural role of phosphate in the CoCat, with these ions binding at the margins of Co-oxide fragments, thereby limiting the long-range material ordering. The relations of catalyst-internal phosphate ions to cobalt’s redox-state changes, proton transfer, and catalytic activity are discussed. Full article

(This article belongs to the Special Issue Electrocatalytic Water Oxidation)

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18 pages, 2124 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Advances in Platinum and Palladium Solvent Extraction from Real Leaching Solutions of Spent Catalysts

by Ana Paula Paiva

Catalysts 2023, 13(7), 1146; https://doi.org/10.3390/catal13071146 - 24 Jul 2023

Cited by 4 | Viewed by 4174

Abstract

The strategic importance of platinum and palladium, two platinum-group metals (PGMs), is particularly supported by their technological applications, one of the most relevant being the role they perform as catalysts for several sorts of chemical reactions. The cumulative demand for these two PGMs [...] Read more.

The strategic importance of platinum and palladium, two platinum-group metals (PGMs), is particularly supported by their technological applications, one of the most relevant being the role they perform as catalysts for several sorts of chemical reactions. The cumulative demand for these two PGMs to be used as catalysts more than justifies increasing research efforts to develop sustainable recycling processes to maintain their supply. This critically appraised topic review describes the recent research trends (since 2010) developed by the world’s research communities to reach sustainable methods to recover platinum and palladium from spent catalysts in the liquid phase, namely those involving a solvent extraction (SX) step. The selected recycling processes are based on extensive fundamental research, but this paper intends to focus on information collected about SX procedures applied to real leaching samples of spent catalysts, either from automobile or industrial sources. A critical appraisal of the claimed success levels, the identified constraints, and open challenges is carried out, together with some perspectives on possible ways to redirect research efforts and minimize the gap between academia and industry on this matter. Full article

(This article belongs to the Special Issue Recent Advances Utilized in the Recycling of Catalysts II)

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15 pages, 3859 KiB

Open AccessEditor’s ChoiceArticle

Photothermal-Assisted Photocatalytic Degradation of Tetracycline in Seawater Based on the Black g-C₃N₄ Nanosheets with Cyano Group Defects

by Loic Jiresse Nguetsa Kuate, Zhouze Chen, Jialin Lu, Huabing Wen, Feng Guo and Weilong Shi

Catalysts 2023, 13(7), 1147; https://doi.org/10.3390/catal13071147 - 24 Jul 2023

Cited by 45 | Viewed by 2357

Abstract

As a broad-spectrum antibiotic, tetracycline (TC) has been continually detected in soil and seawater environments, which poses a great threat to the ecological environment and human health. Herein, a black graphitic carbon nitride (CN-B) photocatalyst was synthesized by the one-step calcination method of [...] Read more.

As a broad-spectrum antibiotic, tetracycline (TC) has been continually detected in soil and seawater environments, which poses a great threat to the ecological environment and human health. Herein, a black graphitic carbon nitride (CN-B) photocatalyst was synthesized by the one-step calcination method of urea and phloxine B for the degradation of tetracycline TC in seawater under visible light irradiation. The experimental results showed that the photocatalytic degradation rate of optimal CN-B-0.1 for TC degradation was 92% at room temperature within 2 h, which was 1.3 times that of pure CN (69%). This excellent photocatalytic degradation performance stems from the following factors: (i) ultrathin nanosheet thickness reduces the charge transfer distance; (ii) the cyanogen defect promotes photogenerated carriers’ separation; (iii) and the photothermal effect of CN-B increases the reaction temperature and enhances the photocatalytic activity. This study provides new insight into the design of photocatalysts for the photothermal-assisted photocatalytic degradation of antibiotic pollutants. Full article

(This article belongs to the Special Issue Development of g-C₃N₄-Based Photocatalysts: Environmental Purification and Energy Conversion)

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23 pages, 7690 KiB

Open AccessEditor’s ChoiceArticle

The Impact of Different Green Synthetic Routes on the Photocatalytic Potential of FeSnO₂ for the Removal of Methylene Blue and Crystal Violet Dyes under Natural Sunlight Exposure

by Arifa Shaukat, Muhammad Akhyar Farrukh, Kok-Keong Chong, Rabia Nawaz, Muhammad Tariq Qamar, Shahid Iqbal, Nasser S. Awwad and Hala A. Ibrahium

Catalysts 2023, 13(7), 1135; https://doi.org/10.3390/catal13071135 - 21 Jul 2023

Cited by 6 | Viewed by 2003

Abstract

FeSnO₂ nanocomposites were synthesized via the green method using aqueous leaf extracts of Lawsonia inermis and Phyllanthus embilica plants. The role of polyphenols based on reduction potentials for the synthesis of FeSnO₂ was also highlighted. The synthesized materials were examined by [...] Read more.

FeSnO₂ nanocomposites were synthesized via the green method using aqueous leaf extracts of Lawsonia inermis and Phyllanthus embilica plants. The role of polyphenols based on reduction potentials for the synthesis of FeSnO₂ was also highlighted. The synthesized materials were examined by using TGA and DSC, FT-IR, XRD, and SEM with EDX analysis. Tetragonal rutile and distorted hexagonal structures were observed in SEM images of the FeSnO₂ nanocomposites and compared with an FeSnO₂ nanocomposite prepared using the sol-gel method. Scherer’s formula yielded crystallite sizes of 29.49, 14.54, and 20.43 nm; however, the average crystallite size assessed employing the Williamson–Hall equation was found to be 20.85, 11.30, and 14.86 nm by using the sol-gel and green techniques, using extracts from Lawsonia inermis and Phyllanthus embilica. The band gap was determined by using the Tauc and Wood equations, and photocatalytic activity was analyzed to determine the degradation of methylene blue (MB) and crystal violet (CV) under the illumination of natural sunlight. It was observed that the sample prepared by means of the green method using the leaf extract of Lawsonia inermis showed the best photocatalytic activity of 84%, with a particle size of 14.54 nm, a 3.10 eV band gap, and a specific surface area of 55.68 m²g⁻¹. Full article

(This article belongs to the Special Issue Advanced Materials for Application in Catalysis)

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17 pages, 4103 KiB

Open AccessEditor’s ChoiceArticle

Facile Synthesis of Silicon-Based Materials Modified Using Zinc(Ⅱ) 2-Bromoacetic as Heterogeneous Catalyst for the Fixation of CO₂ into Cyclic Carbonates

by Chaokun Yang, Xiangning Ma, Meng Li, Tuantuan Yang and Xin Zhao

Catalysts 2023, 13(7), 1116; https://doi.org/10.3390/catal13071116 - 17 Jul 2023

Cited by 3 | Viewed by 1391

Abstract

Much effort has been devoted to the development of efficient heterogeneous catalysts for the conversion of carbon dioxide (CO₂) into high-value chemicals. Generally, the cycloaddition of CO₂ to epoxides is considered a green and atom-economic reaction for the production of [...] Read more.

Much effort has been devoted to the development of efficient heterogeneous catalysts for the conversion of carbon dioxide (CO₂) into high-value chemicals. Generally, the cycloaddition of CO₂ to epoxides is considered a green and atom-economic reaction for the production of cyclic carbonates. Based on this, three kinds of silicon-based catalysts modified using zinc(Ⅱ) 2-bromoacetic (Si-ZnBA-n, n = 1, 2, 3) were facilely synthesized and employed for the chemical fixation of CO₂ to epoxides with the use of potassium iodide (KI). A series of characterization techniques were used to characterize the textual structures and physicochemical properties of Si-ZnBA-n. The synergistic effects of Zn, –NH_2, –OH and the nucleophilic group guaranteed the catalytic activity of Si-ZnBA-n. Si-ZnBA-1 exhibited the best catalytic activity among Si-ZnBA-n because Si-ZnBA-1 possessed the highest Zn content. Additionally, the effects of the reaction conditions (temperature, pressure, time and catalyst loadings) were also discussed. The propylene carbonate (PC) yield could reach 97% under 130 °C, 2 MPa, for 5 h without the employment of organic solvent, and its selectivity was 99%. In addition, the recycling property of Si-ZnBA-1/KI was also investigated, and the catalytic system exhibited good cycle performance. Meanwhile, the catalyst showed outstanding versatility for CO₂ application to various epoxides, and a possibly synergistic reaction mechanism was proposed. Finally, a dynamic model was developed to discuss the activation energy of the CO₂ cycloaddition reaction over the Si-ZnBA-1 catalyst. Full article

(This article belongs to the Special Issue Synthesis and In-Depth Characterization of Supported and Highly Dispersed Catalysts)

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14 pages, 1320 KiB

Open AccessEditor’s ChoiceArticle

Iron(III) Sulfate-Mediated Synthesis of 2,5-Furandicarboxylic Acid Dimethyl Ester from Galactaric Acid

by Giacomo Trapasso, Beatriz Chícharo, Thomas Gherardi, Davide Redolfi-Bristol and Fabio Aricò

Catalysts 2023, 13(7), 1114; https://doi.org/10.3390/catal13071114 - 17 Jul 2023

Cited by 5 | Viewed by 2767

Abstract

2,5-furandicarboxylic acid (FDCA) is one of the most studied bio-based monomers, being considered the best substitute for fossil-derived terephthalic acid in plastic production. FDCA is employed in the preparation of polyethylene furanoate (PEF), demonstrating superior mechanical and thermal proprieties compared to the widely [...] Read more.

2,5-furandicarboxylic acid (FDCA) is one of the most studied bio-based monomers, being considered the best substitute for fossil-derived terephthalic acid in plastic production. FDCA is employed in the preparation of polyethylene furanoate (PEF), demonstrating superior mechanical and thermal proprieties compared to the widely used polyethylene terephthalate (PET). Nevertheless, FDCA synthesis mostly relies on the oxidation of the bio-based platform chemical hydroxymethyl furfural (HMF), whose notoriously instable nature renders FDCA yield and industrial scale-up production complicated. On the contrary, FDCA esters are less studied, even though they have greater solubility in organic media, which would favor their isolation and potential application as monomers for PEF. On these premises, we report herein an alternative green synthetic approach to FDCA methyl ester (FDME) using galactaric acid as the substrate, dimethyl carbonate (DMC) as the green media, and Fe₂(SO₄)₃ as the heterogeneous Lewis acid. Optimization of the reaction conditions allowed the selective production of FDME in a 70% isolated yield; product purification was achieved via flash column chromatography over silica. Furthermore, it was possible to employ up to 5.0 g of galactaric acid in a single reaction, leading to a good isolated yield of FDME. Full article

(This article belongs to the Special Issue Novel Catalytic Strategies for the Synthesis of Furans and Their Derivatives)

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31 pages, 3592 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Molten Metals and Molten Carbonates in Solid Oxide Direct Carbon Fuel Cell Anode Chamber: Liquid Metal Anode and Hybrid Direct Carbon Fuel Cells

by Ermete Antolini

Catalysts 2023, 13(7), 1107; https://doi.org/10.3390/catal13071107 - 15 Jul 2023

Cited by 3 | Viewed by 1797

Abstract

To enhance the contact between the electrolyte (source of O²⁻) and the carbon fuel in solid oxide–direct carbon fuel cells (SO-DCFCs), molten metals and molten salts were used in the anode chamber. Oxygen ions can dissolve and be transported in the [...] Read more.

To enhance the contact between the electrolyte (source of O²⁻) and the carbon fuel in solid oxide–direct carbon fuel cells (SO-DCFCs), molten metals and molten salts were used in the anode chamber. Oxygen ions can dissolve and be transported in the molten medium to the anode three-phase boundary to reach and oxidize the carbon particles. To improve the sluggish kinetics of the electrochemical oxidation of carbon, the same molten media can act as redox mediators. Moreover, using a liquid metal/salt anode, tolerant to fuel impurities, the negative effect of carbon contaminants on cell performance is mitigated. In this work, an overview of SO-DCFCs with liquid metals, liquid carbonates, and mixed liquid metals/liquid carbonates in the anode chamber is presented and their performance was compared to that of conventional SO-DCFCs. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section Electrocatalysis)

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35 pages, 14056 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Progress in Nickel and Silica Containing Catalysts for CO₂ Hydrogenation to CH₄

by Nadiyah Albeladi, Qana A. Alsulami and Katabathini Narasimharao

Catalysts 2023, 13(7), 1104; https://doi.org/10.3390/catal13071104 - 14 Jul 2023

Cited by 6 | Viewed by 2524

Abstract

The recent unusual weather changes occurring in different parts of the world are caused by global warming, a consequence of the release of extreme amounts of greenhouse gases into the atmosphere. Carbon dioxide (CO₂) is one of these greenhouse gasses, which [...] Read more.

The recent unusual weather changes occurring in different parts of the world are caused by global warming, a consequence of the release of extreme amounts of greenhouse gases into the atmosphere. Carbon dioxide (CO₂) is one of these greenhouse gasses, which can be captured and reused to generate fuel through the methanation process. Nickel- and silica-based catalysts have been recognized as promising catalysts due to their efficiency, availability, and low prices. However, these catalysts suffer from metal sintering at high temperatures. Researchers have achieved remarkable improvements through altering conventional synthesis methods, supports, metal loading amounts, and promoters. The modified routes have enhanced stability and activity while the supports offer large surface areas, dispersion, and strong metal–support interactions. Nickel loading affects the formed structure and catalytic activity, whereas doping causes CO₂ conversion at low temperatures and forms basic sites. This review aims to discuss the CO₂ methanation process over Ni- and SiO₂-based catalysts, in particular the silica-supported Ni metal in previously reported research works and point out directions for potential future work. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Fine Chemicals: Development of Sustainable Chemical Processes)

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13 pages, 1057 KiB

Open AccessEditor’s ChoiceArticle

Synthesis of New Dehydrodieugenol Derivatives via Olefin Cross Metathesis and In Vitro Evaluation of Their Trypanocidal Activity

by Thalita S. Galhardo, Anderson K. Ueno, Wagner A. Carvalho, Thais A. Costa-Silva, Marina M. Gonçalves, Mariana B. Abiuzi, Andre G. Tempone, João Henrique G. Lago, Dalmo Mandelli, Cedric Fischmeister and Christian Bruneau

Catalysts 2023, 13(7), 1097; https://doi.org/10.3390/catal13071097 - 13 Jul 2023

Viewed by 1373

Abstract

Ruthenium-catalyzed cross metathesis using biseugenol (1) with electron-deficient olefins methyl (2a) and ethyl (2b) acrylates, acrylic acid (2c), acrylonitrile (2d), and methyl methacrylate (2e) derivatives have been conducted to afford respective [...] Read more.

Ruthenium-catalyzed cross metathesis using biseugenol (1) with electron-deficient olefins methyl (2a) and ethyl (2b) acrylates, acrylic acid (2c), acrylonitrile (2d), and methyl methacrylate (2e) derivatives have been conducted to afford respective derivatives 3a–3e with good yields and excellent conversion rates. Activity of prepared compounds against trypomastigote and amastigote forms of Trypanosoma cruzi and mammalian cytotoxicity have been evaluated. The results obtained indicate that the IC₅₀ values for amastigotes of compounds 3b and 3d are quite similar to those of biseugenol (1), but unlike this compound, they show reduced toxicities with SI values similar to those of the standard drug benznidazol. Full article

(This article belongs to the Section Catalysis for Pharmaceuticals)

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14 pages, 2975 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Understanding the Role of Electrolyte Cations on Activity and Product Selectivity of CO₂ Reduction over Cu Electrode

by Aamir Hassan Shah, Yue Gong, Yanjie Wang, Abebe Reda Woldu and Tao He

Catalysts 2023, 13(7), 1092; https://doi.org/10.3390/catal13071092 - 12 Jul 2023

Cited by 2 | Viewed by 1840

Abstract

The electrocatalytic conversion of CO₂ on a Cu electrode has the potential to produce valuable chemicals such as hydrocarbons and oxygenated compounds. While the influence of electrolyte cation on the activity and selectivity of the CO₂ reduction reaction (CO₂RR) [...] Read more.

The electrocatalytic conversion of CO₂ on a Cu electrode has the potential to produce valuable chemicals such as hydrocarbons and oxygenated compounds. While the influence of electrolyte cation on the activity and selectivity of the CO₂ reduction reaction (CO₂RR) on Cu has been widely observed, the specific mechanism through which cation species affect the CO₂RR remains unclear and subject to debate. In this work, the CO₂RR in the carbonate electrolytes containing different alkali metals (Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺) was investigated at potentials from −0.1 to −1.1 V (vs. RHE) over a Cu electrode using electrochemical techniques. Charge transfer kinetics, adsorption of species, and mass transport were considered comprehensively during the analysis. It is found that several factors can play a role in the CO₂RR, including hydrated cation adsorption, preferential hydrolysis, and interaction between the cation and adsorbed species, with the dominating factor determined by the external bias and cation species. Consequently, a coherent interpretation of the influence of electrolyte cations on the intrinsic kinetics of the CO₂RR has been put forward. We envision that these insights will greatly contribute to the development of efficient catalytic systems and the optimization of catalytic conditions, thereby advancing progress toward commercial applications in this field. Full article

(This article belongs to the Special Issue Application of Catalysts in CO₂ Capture, Production and Utilization)

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15 pages, 6041 KiB

Open AccessEditor’s ChoiceArticle

Facile Synthesis of 3D Interconnected Porous g-C₃N₄/rGO Composite for Hydrogen Production and Dye Elimination

by Congyue Zhao, Hengchao Sun, Chunling Li, Manrong Wang, Jiahang Wu, Minghui Chen, Shuai Jiang, Tianqi Niu and Dong Liu

Catalysts 2023, 13(7), 1079; https://doi.org/10.3390/catal13071079 - 7 Jul 2023

Cited by 4 | Viewed by 1663

Abstract

Photocatalytic materials can effectively decompose water to produce hydrogen and degrade pollutants, ameliorating environmental issues. These materials are currently a popular research topic for addressing energy shortages and water pollution issues worldwide. Herein, we prepared composite catalysts with g-C₃N₄/rGO [...] Read more.

Photocatalytic materials can effectively decompose water to produce hydrogen and degrade pollutants, ameliorating environmental issues. These materials are currently a popular research topic for addressing energy shortages and water pollution issues worldwide. Herein, we prepared composite catalysts with g-C₃N₄/rGO heterojunctions formed via the stacking of reduced graphene oxide (rGO) nanosheets and three-dimensional (3D) carbon nitride, and the catalysts displayed excellent photocatalytic activity in experiments for hydrogen production (4.37 mmol g⁻¹ h⁻¹) and rhodamine B elimination (96.2%). The results of structural characterization showed that the recombination of rGO has no effect on the morphology of g-C₃N₄, and the photochemical characterization results showed that the photogenerated electron migration of the prepared composite was accelerated. Additionally, a possible mechanism of enhancement involving synergy between the 3D structure of the catalyst and the g-C₃N₄/rGO heterojunctions was proposed on the basis of catalyst characterization and photocatalytic experiments. The prepared composite catalysts had large specific surface areas and abundant adsorption sites due to the 3D structure, and the g-C₃N₄/rGO heterojunction provided high electron mobility, resulting in low recombination of photoinduced electron and hole pairs and high conductivity. Moreover, free radical species that may play a substantial role in the photocatalytic process were analyzed via free radical quenching experiments, and possible catalytic mechanisms were presented in this study. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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16 pages, 6808 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Porphyrin Modified UiO-66-NH₂ for Highly Efficient Photoreduction of Cr(VI) under Visible Light

by Kaiwen Yuan, Bo Gong, Chundong Peng, Yanmei Feng, Yingmo Hu, Kai Chen, Daimei Chen and Derek Hao

Catalysts 2023, 13(7), 1073; https://doi.org/10.3390/catal13071073 - 6 Jul 2023

Cited by 9 | Viewed by 2401

Abstract

Cr(VI) is a common heavy metal pollutants present in the aquatic environment, which possess toxic and carcinogenic properties. In this study, a solvothermal reaction was used to prepare porphyrin (TCPP)-modified UiO-66-NH₂ (UNT). The UNT integrated adsorption and photocatalytics in the application for [...] Read more.

Cr(VI) is a common heavy metal pollutants present in the aquatic environment, which possess toxic and carcinogenic properties. In this study, a solvothermal reaction was used to prepare porphyrin (TCPP)-modified UiO-66-NH₂ (UNT). The UNT integrated adsorption and photocatalytics in the application for dealing with Cr(VI). The photocatalytic reduction activities of UNT for Cr(VI) were investigated under visible light illumination. We found that the TCPP doping amount of 15 mg UNT (15-UNT) had a 10 times higher reduction rate of Cr(VI) than pristine UiO-66-NH₂. The optimal 15-UNT photocatalyst demonstrated the highest photocatalytic activity, and Cr(VI) was completely removed within 80 min. In addition, the introduction of porphyrin not only enhanced the absorption of light but also enabled the transport of photogenerated electrons from porphyrin to UiO-66-NH₂, which promoted the separation of charge carriers. Furthermore, the effects of factors such as porphyrin content, pH and light source on the photocatalytic reduction performances of UNT were also explored. Overall, this work presented a possible relationship between the crystal structures and the performance of UNT. Full article

(This article belongs to the Special Issue Recent Progress of Catalysis in “Dual Carbon Targets”)

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16 pages, 5511 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Mild and Sustainable Procedure for the Functionalization of Morpholin-2-Ones by Oxidative Imidation Reactions

by Ana Maria Faisca Phillips and Armando J. L. Pombeiro

Catalysts 2023, 13(7), 1072; https://doi.org/10.3390/catal13071072 - 5 Jul 2023

Viewed by 1376

Abstract

Nitrogen-containing heterocycles such as morpholin-2-ones are structural elements of many biologically active substances, as well as useful synthetic intermediates. To be able to functionalize them regioselectively in an easy, atom-efficient, and environmentally friendly manner is highly desirable. A procedure for cross-dehydrogenative coupling between [...] Read more.

Nitrogen-containing heterocycles such as morpholin-2-ones are structural elements of many biologically active substances, as well as useful synthetic intermediates. To be able to functionalize them regioselectively in an easy, atom-efficient, and environmentally friendly manner is highly desirable. A procedure for cross-dehydrogenative coupling between morpholinones and cyclic imides was developed addressing these requirements. An earth-abundant metal catalyst, copper(I) chloride, in the presence of acetic acid, and with molecular oxygen as the sole oxidant, operating under mild conditions, afforded the desired C–N coupled products in high yields. Besides being potentially biologically active, as many members of both families of compounds are, the products themselves may be suitable substrates for functionalized polymers, e.g., poly(β-aminoesters) or even for PROTACs. Full article

(This article belongs to the Special Issue Advances in Green Catalysis for Sustainable Organic Synthesis, 2nd Edition)

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11 pages, 3747 KiB

Open AccessEditor’s ChoiceArticle

Enhancing the Activity of Cu-MOR by Water for Oxidation of Methane to Methanol

by Xi’an Guan, Yehong Wang, Xiumei Liu, Hong Du, Xinwen Guo and Zongchao Zhang

Catalysts 2023, 13(7), 1066; https://doi.org/10.3390/catal13071066 - 3 Jul 2023

Cited by 2 | Viewed by 1608

Abstract

As clean energy, methane has huge reserves and great development potential in the future. Copper zeolites are efficient in the oxidation of methane to methanol. Water has been confirmed as a source of oxygen to regenerate the copper-zeolite active sites to enable selective [...] Read more.

As clean energy, methane has huge reserves and great development potential in the future. Copper zeolites are efficient in the oxidation of methane to methanol. Water has been confirmed as a source of oxygen to regenerate the copper-zeolite active sites to enable selective anaerobic oxidation of methane to methanol. In this work, we report that the methanol yield increased from 36 μmol/g (Cu-MOR₁) to 92 μmol/g (Cu-MOR₁-water) as a result of water enhancing the activity of copper ion-exchange mordenite catalyst. We show for the first time that water could convert inactive copper species into active copper species during catalyst activation. A combination of the XPS, FTIR, and NMR results indicates that water dissociates and then converts ZCu^IIZ into ZCu^II(OH) (where Z indicates framework O (O_fw) bonded to one isolated Al in a framework T-site, i.e., 1Al) and simultaneously produces a Brönsted acid site during catalyst activation. This finding can be used to tune the state of copper species and design highly active copper-zeolite catalysts for methane oxidation to methanol. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Clean Energy Production and Carbon Dioxide Utilization)

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14 pages, 4226 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

“Pharaoh’s Snakes” Reaction-Derived Carbon with Favorable Structure and Composition as Metal-Free Oxygen Reduction Reaction Electrocatalyst

by Yuan Li, Xinyao Wang, Hong Wang, Xiaoyao Tan, Dan Liu, Jianzhou Gui, Jian Gao, Zhen Yin, Na Ma and Yun Wang

Catalysts 2023, 13(7), 1059; https://doi.org/10.3390/catal13071059 - 30 Jun 2023

Cited by 2 | Viewed by 1403

Abstract

Metal-air batteries rely on the oxygen reduction reaction (ORR) for their operation. However, the ORR is kinetically slow, necessitating the use of Pt-based catalysts, which is hindered by their high cost and limited availability. Consequently, considerable efforts have been dedicated to developing metal-free [...] Read more.

Metal-air batteries rely on the oxygen reduction reaction (ORR) for their operation. However, the ORR is kinetically slow, necessitating the use of Pt-based catalysts, which is hindered by their high cost and limited availability. Consequently, considerable efforts have been dedicated to developing metal-free catalysts for the ORR. Among these, heteroatom-doped carbons have emerged as promising candidates by manipulating their composition and microstructure. Inspired by the ancient “Pharaoh’s snakes” reaction, this study utilized sugar, melamine, and a polymerizable ionic liquid as precursors to prepare heteroatom-doped carbons with the desired composition and structure. The resulting carbon catalyst exhibited an onset potential and half-wave potential in a 0.1 M KOH electrolyte that was comparable to those of a commercial Pt/C 20 wt.% catalyst, with values of 0.97 and 0.83 V_RHE, respectively. Furthermore, the catalyst demonstrated excellent stability, retaining 93% of its initial current after a 10,800-s test. To evaluate its practical application, the synthesized carbon was employed as the cathode catalyst in a Zn-air battery, which achieved a maximum power density of 90 mW cm⁻². This study, therefore, presents a simple yet effective method for producing metal-free heteroatom-doped carbon ORR catalysts used in various energy conversion and storage devices. Full article

(This article belongs to the Special Issue Research Advances in Electrocatalysis and Energy-Related Findings across Asia-Pacific)

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20 pages, 2092 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Pesticides in Foods: Towards Bioremediation Biocatalysts?

by Giorgia Perpetuini, Pilar Anais Nzobouh Fossi, Seyi Kwak, Oscar Namessi, Awanwee Petchkongkaew, Rosanna Tofalo and Yves Waché

Catalysts 2023, 13(7), 1055; https://doi.org/10.3390/catal13071055 - 29 Jun 2023

Cited by 4 | Viewed by 3074

Abstract

The presence of hazardous chemical compounds in foods is a growing concern in almost every country. Although some toxins come from microbial contamination, a major part comes from residues of pesticides used for plant health and food preservation. Despite plans to decrease their [...] Read more.

The presence of hazardous chemical compounds in foods is a growing concern in almost every country. Although some toxins come from microbial contamination, a major part comes from residues of pesticides used for plant health and food preservation. Despite plans to decrease their use, the concentration of hazardous residues encountered in food is growing. The societal solution to this issue is to find alternatives to chemicals and replace the most hazardous by biodegradable, fewer toxic compounds. However, as this greener transition takes some time, any transitory solution to decrease the risks of contamination is welcome. Among them, the stimulation of microbial pesticide degradation in food in a similar way to bioremediation in the environment would be very positive. In this review, we present the problem of food contamination, focusing on organophosphates and organochlorines, and the various possibilities of microbial decontamination. We discuss the possible use of microbial biocatalysts as a biopreservation tool. We conclude that, although this process is very promising, it lacks research taking into account the various degradation products and the elaboration of screening procedures able to choose some rare, efficient biopreservation strains. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Green Catalysts)

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14 pages, 1885 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Electrocatalytic Hydrodechlorination Using Supported Atomically Precise Gold Nanoclusters under Flow-Through Configuration

by Zhiyuan Zhao, Haochen Yan, Fuqiang Liu, Jie Yao, Shijie You and Yanbiao Liu

Catalysts 2023, 13(7), 1045; https://doi.org/10.3390/catal13071045 - 28 Jun 2023

Cited by 3 | Viewed by 1469

Abstract

We developed and optimized an electrocatalytic filtration system to catalytically hydrodechlorinate chlorophenolic compounds. A key part of the system was the cathode, which consisted of a filter constructed with electroactive carbon nanotubes (CNTs) functionalized with atomically precise gold nanoclusters (AuNCs). In the functional [...] Read more.

We developed and optimized an electrocatalytic filtration system to catalytically hydrodechlorinate chlorophenolic compounds. A key part of the system was the cathode, which consisted of a filter constructed with electroactive carbon nanotubes (CNTs) functionalized with atomically precise gold nanoclusters (AuNCs). In the functional membrane electrode, the AuNCs attached to the CNTs functioned as a highly effective hydrodechlorination catalyst. Additionally, the ligands of the AuNCs facilitated the binding of the AuNCs with the CNT and protected the Au core from agglomeration. Atomic H* was the primary reactive species in the system, but direct reduction by cathode electrons also contributed to the elimination of 2,4-dichlorophenol (2,4-DCP) by hydrodechlorination. The generated atomic H* was able to break the C–Cl bond to achieve the rapid hydrodechlorination of 2,4-DCP into phenol, with 91.5% 2,4-DCP removal within 120 min. The AuNC catalysts attached to the CNT exceeded the best catalytic activity of larger nanoparticles (e.g., AuNPs), while the flow-through construction performed better than a standard batch reactor due to the convection-enhanced mass transport. The study provides an environmentally friendly strategy for the elimination of pervasive halogenated organic contaminants using a highly efficient, stable and recyclable system for hydrodechlorination that integrates nanofiltration and electrochemistry. Full article

(This article belongs to the Section Electrocatalysis)

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24 pages, 12197 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Chiral Porous Organic Frameworks: Synthesis, Chiroptical Properties, and Asymmetric Organocatalytic Applications

by Miguel Sanchez-Fuente, José Lorenzo Alonso-Gómez, Laura M. Salonen, Ruben Mas-Ballesté and Alicia Moya

Catalysts 2023, 13(7), 1042; https://doi.org/10.3390/catal13071042 - 27 Jun 2023

Cited by 4 | Viewed by 2760

Abstract

Chiral porous organic frameworks have emerged in the last decade as candidates for heterogeneous asymmetric organocatalysis. This review aims to provide a summary of the synthetic strategies towards the design of chiral organic materials, the characterization techniques used to evaluate their chirality, and [...] Read more.

Chiral porous organic frameworks have emerged in the last decade as candidates for heterogeneous asymmetric organocatalysis. This review aims to provide a summary of the synthetic strategies towards the design of chiral organic materials, the characterization techniques used to evaluate their chirality, and their applications in asymmetric organocatalysis. We briefly describe the types of porous organic frameworks, including crystalline (covalent organic frameworks, COFs) and amorphous (conjugated microporous polymers, CMPs; covalent triazine frameworks, CTFs and porous aromatic frameworks, PAFs) materials. Furthermore, the strategies reported to incorporate chirality in porous organic materials are presented. We finally focus on the applications of chiral porous organic frameworks in asymmetric organocatalytic reactions, summarizing and categorizing all the available literature in the field. Full article

(This article belongs to the Special Issue Exclusive Review Papers in Catalysis in Organic and Polymer Chemistry)

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14 pages, 2815 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Explicit Water Molecules on the Electrochemical Hydrogenation of CO₂ on Sn(112)

by Jia Wang, Chaonan Cui, Xinli Zhu, Hua Wang and Qingfeng Ge

Catalysts 2023, 13(7), 1033; https://doi.org/10.3390/catal13071033 - 23 Jun 2023

Cited by 2 | Viewed by 1688

Abstract

Water is typically treated as an implicit solvent in modeling electrochemical reactions in an aqueous environment. Such treatment may not be adequate, as a series of concerted or sequential proton-electron transfer steps that explicitly involve water molecules are likely to play important roles [...] Read more.

Water is typically treated as an implicit solvent in modeling electrochemical reactions in an aqueous environment. Such treatment may not be adequate, as a series of concerted or sequential proton-electron transfer steps that explicitly involve water molecules are likely to play important roles in a reaction, such as the electrochemical hydrogenation of CO₂. Herein, we use the electrochemical hydrogenation of CO₂ on the Sn(112) surface as a model, and employ the density functional theory (DFT) method to examine the effect of up to 12 explicit water molecules on the stability of the hydrogenation intermediates. Our results show that six water molecules are needed to account for the local interaction between an intermediate and the water solvent. Furthermore, the hydrogen bonding interaction between the explicit water molecules and intermediates causes a significant stabilization to the O-containing intermediates, such as the HCOO* and CHO* + OH* species. The inclusion of explicit water molecules also altered the prediction of the potential-limiting step from the formation of H* atoms without the explicit water molecules to the formation of H₂COO* in the presence of water molecules and increased selectivity towards methane. This work provides useful insights into the electrocatalytic hydrogenation of CO₂, emphasizing the importance of including explicit water molecules to account for the hydrogen bonding interaction between solvent water molecules and the reaction intermediates. Full article

(This article belongs to the Special Issue Catalysis for Selective Hydrogenation of CO and CO₂)

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11 pages, 2536 KiB

Open AccessEditor’s ChoiceCommunication

Long-Term Hydrogen Production from a Methanol–Water Solution Catalyzed by an Iridium Complex

by Shohichi Furukawa, Kaito Kubota, Han Wang, Haotong Gong, Shumpei Kajita and Ken-ichi Fujita

Catalysts 2023, 13(6), 1027; https://doi.org/10.3390/catal13061027 - 20 Jun 2023

Cited by 1 | Viewed by 1784

Abstract

Long-term hydrogen production from a methanol–water solution was achieved by developing a new reaction system employing a homogeneous iridium catalyst bearing a bipyridonate-type functional ligand. By optimizing the methanol:water ratio of the reaction solution, the efficiency of hydrogen production was greatly improved in [...] Read more.

Long-term hydrogen production from a methanol–water solution was achieved by developing a new reaction system employing a homogeneous iridium catalyst bearing a bipyridonate-type functional ligand. By optimizing the methanol:water ratio of the reaction solution, the efficiency of hydrogen production was greatly improved in relation to that reported in our previous studies. Additionally, the effect of the scale of reaction was investigated. It was found that a small-scale reaction led to a longer lifetime of the iridium catalyst, accomplishing long-term continuous hydrogen production at a constant rate for over 500 h. Furthermore, procedures for catalyst reuse were studied. After hydrogen production for 400 h, all volatiles in the reaction system were removed under vacuum. This simple procedure is highly effective for the reactivation and reuse of the catalyst. Finally, hydrogen production (13.7 L, 562 mmol) from methanol (12.3 mL, 303 mmol) and water (5.46 mL, 303 mmol), in a continuous reaction for 800 h, was achieved. Full article

(This article belongs to the Special Issue Advances in Reforming Catalysts for Hydrogen Production)

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14 pages, 3385 KiB

Open AccessEditor’s ChoiceArticle

Fe-N-C Catalyst Derived from MOFs with Enhanced Catalytic Performance for Selective Oxidation of Emerging Contaminants

by Cheng Zeng, Yan Wang, Jinquan Wan and Zhicheng Yan

Catalysts 2023, 13(6), 1021; https://doi.org/10.3390/catal13061021 - 19 Jun 2023

Cited by 2 | Viewed by 1609

Abstract

Fe-N-C/peroxymonosulfate (PMS) systems have demonstrated selective oxidation of pollutants, but the underlying mechanism and reasons for variability remain unclear. In this work, we synthesized a highly active Fe-N-C catalyst derived from MOFs using a pyrolysis protection strategy. We assessed its catalytic activity by [...] Read more.

Fe-N-C/peroxymonosulfate (PMS) systems have demonstrated selective oxidation of pollutants, but the underlying mechanism and reasons for variability remain unclear. In this work, we synthesized a highly active Fe-N-C catalyst derived from MOFs using a pyrolysis protection strategy. We assessed its catalytic activity by employing PMS as an activator for pollutant degradation. The presence of Fe-Nx sites favored the catalytic performance of FeMIL-N-C, exhibiting 23 times higher activity compared to N-C. Moreover, we investigated the degradation performance and mechanism of the FeMIL-N-C/PMS system through both experimental and theoretical analyses, focusing on pollutants with diverse electronic structures, namely bisphenol A (BPA) and atrazine (ATZ)N-C. Our findings revealed that the degradation of ATZ primarily follows the free radical pathway, whereas BPA degradation is dominated by electron transfer pathways. Specifically, pollutants with a low LUMO- HOMO energy gap (BPA) can be degraded via the FeMIL-N-C/PMS system through the electron transfer pathway. Conversely, pollutants with a high LUMO-HOMO energy gap (ATZ) exhibit limited electron donation and predominantly undergo degradation through the free radical pathway. This work introduces novel insights into the mechanisms underlying the selective oxidation of pollutants, facilitating a deeper understanding of effective pollutant removal strategies. Full article

(This article belongs to the Special Issue Advanced Catalytic Technology for Environmental Pollution Control)

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11 pages, 2813 KiB

Open AccessEditor’s ChoiceArticle

Laser Irradiation-Induced Pt-Based Bimetallic Alloy Nanostructures without Chemical Reducing Agents for Hydrogen Evolution Reaction

by Taiping Hu, Yisong Fan, Yixing Ye, Yunyu Cai, Jun Liu, Yao Ma, Pengfei Li and Changhao Liang

Catalysts 2023, 13(6), 1018; https://doi.org/10.3390/catal13061018 - 18 Jun 2023

Cited by 4 | Viewed by 1705

Abstract

Binary metallic alloy nanomaterials (NMs) have received significant attention because of their widespread application in photoelectrocatalysis, electronics, and engineering. Although various synthetic methods have been adopted to prepare binary alloy NMs, the formation of bimetallic alloy NMs by irradiating the mixed solutions of [...] Read more.

Binary metallic alloy nanomaterials (NMs) have received significant attention because of their widespread application in photoelectrocatalysis, electronics, and engineering. Although various synthetic methods have been adopted to prepare binary alloy NMs, the formation of bimetallic alloy NMs by irradiating the mixed solutions of metal salts and metal powders, using a nanosecond pulsed laser in the absence of any reducing agent, is rarely reported. Herein, we report a simple method to fabricate PtX (X = Ag, Cu, Co, Ni) alloy NMs by laser irradiation. Taking PtAg alloys as an example, we present the growth dynamics of the PtAg alloys by laser irradiating a mixture solution of bulk Pt and AgNO₃. The experimental process and evidenced characterization indicate that the photothermal evaporation induced by laser irradiation can cause the fragmentation of the bulk Pt into smaller parts, which alloy with Ag atoms extracted from Ag⁺ by solvated electrons (e⁻_aq) and free radicals (H_aq). These alloys were used as electrocatalysts for the hydrogen evolution reaction (HER), proving their potential application. Notably, in a 0.5 M H₂SO₄ solution, the PtNi alloy exhibited higher HER activity (44 mV at 10 mA/cm⁻²) compared to the untreated bulk Pt (72 mV). Our work provides unique insights into the growth processing of valuable Pt-based bimetallic alloy NMs by laser-assisted metallic alloying, which paves a path for the development of bimetallic alloy electrocatalysts. Full article

(This article belongs to the Special Issue Advances in Photocatalysis and Electrocatalysis Applications)

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16 pages, 4991 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Electrochemical Promotion of CO₂ Hydrogenation Using Rh Catalysts Supported on O²⁻ Conducting Solid Electrolyte

by Nikoleta Kokkinou, Fotios Xydas, Susanne Brosda, Georgios Kyriakou and Alexandros Katsaounis

Catalysts 2023, 13(6), 1014; https://doi.org/10.3390/catal13061014 - 16 Jun 2023

Cited by 2 | Viewed by 1235

Abstract

Electrochemical promotion was used to modify the activity and selectivity of a Rh catalyst electrode in the CO₂ hydrogenation reaction. The experiments were carried out in a temperature range of 350–430 °C at ambient pressure and at different CO₂ to H [...] Read more.

Electrochemical promotion was used to modify the activity and selectivity of a Rh catalyst electrode in the CO₂ hydrogenation reaction. The experiments were carried out in a temperature range of 350–430 °C at ambient pressure and at different CO₂ to H₂ gas feeding ratios (1:2 to 4:1). The only reaction products observed were CO and CH₄, both under open- and closed-circuit conditions. The CH₄ formation rate was found to increase with both positive and negative potential or current application. The CO formation rate followed the opposite trend. The selectivity to CH₄ increased under high values of hydrogen partial pressure and decreased at high pressures of CO₂. The results demonstrate how electrochemical promotion can be used to finely tune activity and selectivity for a reaction of high technical and environmental importance. Full article

(This article belongs to the Special Issue Innovative Catalytic Materials for Environmental Remediation and Energy Applications)

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16 pages, 28979 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Self-Supporting NiMn-LDHs/rGO/NF Composite Electrode Showing Much Enhanced Electrocatalytic Performance for Oxygen Evolution Reaction

by Jia Wang and Yongfu Lian

Catalysts 2023, 13(6), 1012; https://doi.org/10.3390/catal13061012 - 16 Jun 2023

Cited by 2 | Viewed by 1609

Abstract

The poor conductivity and instability of layered dihydroxides (LDHs) limit their widespread application in oxygen evolution reaction (OER). In this study, the composite electrode of NiMn-LDHs, reduced graphene oxide (rGO) and nickel foam (NF), i.e., NiMn-LDHs/rGO/NF, was prepared by a hydrothermal method. When [...] Read more.

The poor conductivity and instability of layered dihydroxides (LDHs) limit their widespread application in oxygen evolution reaction (OER). In this study, the composite electrode of NiMn-LDHs, reduced graphene oxide (rGO) and nickel foam (NF), i.e., NiMn-LDHs/rGO/NF, was prepared by a hydrothermal method. When subjected to oxygen evolution reaction (OER) catalytic performance in a solution of 1 M KOH, the NiMn-LDHs/rGO/NF composite catalyst exhibited an overpotential of only 140 mV at a current density of 10 mA cm⁻² and a Tafel slope of 49 mV dec⁻¹, which is not only better than the comparing RuO₂/NF catalyst, but also better than most of the Mn-based and the Ni–Fe-containing bimetallic OER catalysts reported in the literature. The excellent electrocatalytic performance is ascribed to the efficient integration of ultrathin NiMn-LDH sheets, thin-layered rGO and NF, contributing significantly to the decrease in charge transfer resistance and the increase in electrochemically active surface area. Moreover, NF plays a role of current collector and a role of rigid support for the NiMn-LDHs/rGO composite, contributing extra conductivity and stability to the NiMn-LDHs/rGO/NF composite electrode. Full article

(This article belongs to the Special Issue Carbon-Based Materials as Efficient Electrocatalysts for Oxygen Evolution Reaction)

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12 pages, 2972 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Identification of Cytochrome P450 Enzymes Responsible for Oxidative Metabolism of Synthetic Cannabinoid (1-Hexyl-1H-Indol-3-yl)-1-naphthalenyl-methanone (JWH-019)

by Ngoc Tran, William E. Fantegrossi, Keith R. McCain, Xinwen Wang and Ryoichi Fujiwara

Catalysts 2023, 13(6), 1008; https://doi.org/10.3390/catal13061008 - 15 Jun 2023

Viewed by 1575

Abstract

(1-Hexyl-1H-indol-3-yl)-1-naphthalenyl-methanone (JWH-019) is one of the second-generation synthetic cannabinoids which as a group have been associated with severe adverse reactions in humans. Although metabolic activation can be involved in the mechanism of action, the metabolic pathway of JWH-019 has not been [...] Read more.

(1-Hexyl-1H-indol-3-yl)-1-naphthalenyl-methanone (JWH-019) is one of the second-generation synthetic cannabinoids which as a group have been associated with severe adverse reactions in humans. Although metabolic activation can be involved in the mechanism of action, the metabolic pathway of JWH-019 has not been fully investigated. In the present study, we aimed to identify the enzymes involved in the metabolism of JWH-019. JWH-019 was incubated with human liver microsomes (HLMs) and recombinant cytochrome P450s (P450s or CYPs). An animal study was also conducted to determine the contribution of the metabolic reaction to the onset of action. Using an ultra-performance liquid chromatography system connected to a single-quadrupole mass detector, we identified 6-OH JWH-019 as the main oxidative metabolite in HLMs supplemented with NADPH. JWH-019 was extensively metabolized to 6-OH JWH-019 in HLMs with the K_M and V_max values of 31.5 µM and 432.0 pmol/min/mg. The relative activity factor method estimated that CYP1A2 is the primary contributor to the metabolic reaction in the human liver. The animal study revealed that JWH-019 had a slower onset of action compared to natural and other synthetic cannabinoids. CYP1A2 mediates the metabolic activation of JWH-019, contributing to the slower onset of its pharmacological action. Full article

(This article belongs to the Special Issue Enzymes in Biomedical, Cosmetic and Food Application)

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11 pages, 2330 KiB

Open AccessEditor’s ChoiceArticle

Exsolved Nanoparticles Decorated Double Perovskites as High-Performance Anodes for Direct-Ammonia Solid Oxide Fuel Cells

by Yongning Yi, Jiaming Chen, Meigui Xu, Guangming Yang, Ran Ran, Wei Zhou, Wei Wang and Zongping Shao

Catalysts 2023, 13(6), 996; https://doi.org/10.3390/catal13060996 - 12 Jun 2023

Cited by 8 | Viewed by 2388

Abstract

Due to the high energy density, mature production technology, ease of storage and transportation, and the no carbon/sulfur nature of ammonia fuel, direct-ammonia solid oxide fuel cells (DA-SOFCs) have received rapidly increasing attention, showing distinct advantages over H₂-fueled SOFCs and low-temperature [...] Read more.

Due to the high energy density, mature production technology, ease of storage and transportation, and the no carbon/sulfur nature of ammonia fuel, direct-ammonia solid oxide fuel cells (DA-SOFCs) have received rapidly increasing attention, showing distinct advantages over H₂-fueled SOFCs and low-temperature fuel cells. However, DA-SOFCs with conventional Ni-based cermet anodes still suffer from several drawbacks, including serious sintering and inferior activity for ammonia decomposition, strongly limiting the large-scale applications. To tackle the above-mentioned issues, exsolved NiCo nanoparticles decorated double perovskite oxides are fabricated and employed as high-performance anodes for DA-SOFCs in this work. By optimizing the Ni doping amount in Sr₂CoMo_1−xNi_xO_6−δ (x = 0.1, 0.2 and 0.3), the reduced Sr₂CoMo_0.8Ni_0.2O_6−δ (r-SCMN2) anode exhibits superb catalytic activity for ammonia cracking reaction and high anti-sintering capability. More specifically, the electrolyte-supported single cell with r-SCMN2 nanocomposite anode delivers superior power outputs and operational durability in ammonia fuel as compared with other r-SCMN anodes owing to the significantly promoted nanoparticle exsolution and stronger interaction between alloy nanoparticles and the support. In summary, this study presents an effective strategy for the design of efficient and stable nanocomposite anodes for DA-SOFCs. Full article

(This article belongs to the Special Issue Research Advances in Electrocatalysts for Fuel Cells)

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12 pages, 1936 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Calcination Conditions on Co₃O₄ Catalysts in the Total Oxidation of Toluene and Propane

by Weidong Zhang, Claude Descorme, Jose Luis Valverde and Anne Giroir-Fendler

Catalysts 2023, 13(6), 992; https://doi.org/10.3390/catal13060992 - 9 Jun 2023

Cited by 3 | Viewed by 1541

Abstract

Co₃O₄ catalysts were prepared via carbonate precipitation and subsequent calcination under specific conditions. The different catalysts were characterized as received using several techniques and tested in the total oxidation of toluene or propane. Calcination at low temperature or under dynamic [...] Read more.

Co₃O₄ catalysts were prepared via carbonate precipitation and subsequent calcination under specific conditions. The different catalysts were characterized as received using several techniques and tested in the total oxidation of toluene or propane. Calcination at low temperature or under dynamic conditions resulted in Co₃O₄ catalysts with small crystallite sizes and large surface areas. The performances of the Co₃O₄ catalysts appeared to be closely related to the low-temperature reducibility. The best catalyst, Co-350D, showed a toluene oxidation rate of 44.5 nmol g⁻¹ s⁻¹ at 200 °C and a propane oxidation rate of 54.0 nmol g⁻¹ s⁻¹ at 150 °C. Meanwhile, Co-350D exhibited excellent cycling stability and decent long-term durability in both reactions. Full article

(This article belongs to the Section Environmental Catalysis)

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14 pages, 5096 KiB

Open AccessEditor’s ChoiceArticle

Preparation of Mn-Co-MCM-41 Molecular Sieve with Thermosensitive Template and Its Degradation Performance for Rhodamine B

by Wenju Peng, Lixia Cai, Yani Lu and Yaoyao Zhang

Catalysts 2023, 13(6), 991; https://doi.org/10.3390/catal13060991 - 9 Jun 2023

Cited by 3 | Viewed by 1440

Abstract

Rhodamine B (RhB) in dyes is widely used in various industries, but it poses a great threat to the natural environment and human health. In this work, a series of thermosensitive polymer materials, PN_xD_y, with controllable morphology and particle [...] Read more.

Rhodamine B (RhB) in dyes is widely used in various industries, but it poses a great threat to the natural environment and human health. In this work, a series of thermosensitive polymer materials, PN_xD_y, with controllable morphology and particle size were prepared by free radical polymerization using N-isopropylacrylamide and N,N-dimethylacrylamide as monomers. Then, by using PN_xD_y as a template, bimetallic Mn- and Co-doped MCM-41 molecular sieves with good morphology and properties were prepared by the microwave-assisted hydrothermal method. The effects of a series of thermosensitive templates on the morphology and properties of the Mn-Co-MCM-41 molecular sieve were investigated. The results demonstrated that the Mn-Co-MCM-41 by PN₁₀₀D₄ as a templating agent showed the best mesoporous ordering and the most regular material morphology with 2 nm nanoparticles. In addition, the molecular sieve with the best structure was selected for the RhB degradation experiments. The Mn-Co-MCM-41 with PN₁₀₀D₄ as the template showed regular morphology and uniform pore channels. It was applied as a catalyst for the degradation of RhB by potassium monopersulfate (PMS). The degradation rate of RhB could reach 98% with a 20 min reaction by Mn-Co-MCM-41 (PN₁₀₀D₄). Meanwhile, the degradation rate could be maintained at 91% after being reused six times. The bimetallic-doped Mn-Co-MCM-41 molecular sieves prepared using the thermosensitive material PN₁₀₀D₄ as a template have good catalytic performance and can be effectively reused. Full article

(This article belongs to the Special Issue Advanced Catalytic Material for Water Treatment)

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14 pages, 5706 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

α-NiS/g-C₃N₄ Nanocomposites for Photocatalytic Hydrogen Evolution and Degradation of Tetracycline Hydrochloride

by Huajin Qi, Chenyu Wang, Luping Shen, Hongmei Wang, Yuan Lian, Huanxia Zhang, Hongxia Ma, Yong Zhang and Jin Zhong Zhang

Catalysts 2023, 13(6), 983; https://doi.org/10.3390/catal13060983 - 8 Jun 2023

Cited by 12 | Viewed by 1810

Abstract

α-NiS/g-C₃N₄ nanocomposites were synthesized and used for photocatalytic hydrogen (H₂) evolution and tetracycline hydrochloride (TC) degradation. The fabricated nanocomposites were characterized by XRD, XPS, SEM, TEM, UV-vis DRS, TRPL, and PEC measurements. Photocatalytic studies show that the hydrogen [...] Read more.

α-NiS/g-C₃N₄ nanocomposites were synthesized and used for photocatalytic hydrogen (H₂) evolution and tetracycline hydrochloride (TC) degradation. The fabricated nanocomposites were characterized by XRD, XPS, SEM, TEM, UV-vis DRS, TRPL, and PEC measurements. Photocatalytic studies show that the hydrogen generation rate of the 15%-α-NiS/g-C₃N₄ nanocomposite reaches 4025 μmol·g⁻¹·h⁻¹ and TC degradation rate 64.6% within 120 min, both of which are higher than that of g-C₃N₄. The enhanced performance of the nanocomposite is attributed to the formation of a heterojunction between α-NiS and g-C₃N₄ that enhances visible light absorption, promotes the separation and transfer of charges, and inhibits the recombination of carriers. The photocatalytic mechanism of the α-NiS/g-C₃N₄ heterojunction nanocomposite is discussed in terms of relevant energy levels and charge transfer processes. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Clean Energy Production and Carbon Dioxide Utilization)

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13 pages, 3452 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Formic Acid Dehydrogenation over a Monometallic Pd and Bimetallic Pd:Co Catalyst Supported on Activated Carbon

by María Ribota Peláez, E. Ruiz-López, M. I. Domínguez, S. Ivanova and M. A. Centeno

Catalysts 2023, 13(6), 977; https://doi.org/10.3390/catal13060977 - 6 Jun 2023

Cited by 5 | Viewed by 2435

Abstract

In this study, palladium is proposed as an active site for formic acid dehydrogenation reaction. Pd activity was modulated with Co metal with the final aim of finding a synergistic effect that makes possible efficient hydrogen production for a low noble metal content. [...] Read more.

In this study, palladium is proposed as an active site for formic acid dehydrogenation reaction. Pd activity was modulated with Co metal with the final aim of finding a synergistic effect that makes possible efficient hydrogen production for a low noble metal content. For the monometallic catalysts, the metal loadings were optimized, and the increase in the reaction temperature and presence of additives were carefully considered. The present study aimed, to a great extent, to enlighten the possible routes for decreasing noble metal loading in view of the better sustainability of hydrogen production from liquid organic carrier molecules, such as formic acid. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Green Catalysts)

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26 pages, 4406 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Research Progress of ZnIn₂S₄-Based Catalysts for Photocatalytic Overall Water Splitting

by Yujie Yan, Zhouze Chen, Xiaofang Cheng and Weilong Shi

Catalysts 2023, 13(6), 967; https://doi.org/10.3390/catal13060967 - 2 Jun 2023

Cited by 15 | Viewed by 3093

Abstract

Photocatalytic overall water splitting in solar–chemical energy conversion can effectively mitigate environmental pollution and resource depletion. Stable ternary metal indium zinc sulfide (ZnIn₂S₄) is considered one of the ideal materials for photocatalytic overall water splitting due to its unique [...] Read more.

Photocatalytic overall water splitting in solar–chemical energy conversion can effectively mitigate environmental pollution and resource depletion. Stable ternary metal indium zinc sulfide (ZnIn₂S₄) is considered one of the ideal materials for photocatalytic overall water splitting due to its unique electronic and optical properties, as well as suitable conduction and valence band positions for suitable photocatalytic overall water splitting, and it has attracted widespread researcher interest. Herein, we first briefly describe the mechanism of photocatalytic overall water splitting, and then introduce the properties of ZnIn₂S₄ including crystal structure, energy band structure, as well as the main synthetic methods and morphology. Subsequently, we systematically summarize the research progress of ZnIn₂S₄-based photocatalysts to achieve overall water splitting through modification methods such as defect engineering, heterostructure construction, and co-catalyst loading. Finally, we provide insights into the prospects and challenges for the overall water splitting of ZnIn₂S₄-based photocatalysts. Full article

(This article belongs to the Special Issue Photocatalysts for Hydrogen Evolution Reaction Based on ZnIn₂S₄ Materials)

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14 pages, 2991 KiB

Open AccessEditor’s ChoiceArticle

Self-Assembly of Porous Hierarchical BiOBr Sub-Microspheres for Efficient Aerobic Photooxidation of Benzyl Alcohol under Simulated Sunlight Irradiation

by Zhigang Wang, Cheng Liu, Fengxi Chen and Rong Chen

Catalysts 2023, 13(6), 958; https://doi.org/10.3390/catal13060958 - 1 Jun 2023

Cited by 3 | Viewed by 1494

Abstract

Semiconductor photocatalytic performances can be modulated through morphology modification. Herein porous hierarchical BiOBr microspheres (BiOBr-MS) of ~3 μm was firstly self-assembled without the assistance of a template via a facile solvothermal synthesis in triethylene glycol (TEG) at 150 °C for 3 h. KBrO [...] Read more.

Semiconductor photocatalytic performances can be modulated through morphology modification. Herein porous hierarchical BiOBr microspheres (BiOBr-MS) of ~3 μm was firstly self-assembled without the assistance of a template via a facile solvothermal synthesis in triethylene glycol (TEG) at 150 °C for 3 h. KBrO₃ was exploited as a bromine source, which slowly provided bromide ions upon reduction in TEG and controlled the growth and self-assembly of primary BiOBr nanoplates. The addition of PVP during solvothermal synthesis of BiOBr-MS reduced the particle size by about three-fold to generate BiOBr sub-microspheres (BiOBr-sMS) of <1 μm. BiOBr-sMS exhibited significantly higher photocatalytic activity than BiOBr-MS for aerobic photooxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) under simulated sunlight irradiation (conversions of BzOH (50 mM) over BiOBr-sMS and BiOBr-MS were, respectively, 51.3% and 29.6% with 100% selectivity to BzH after Xenon illumination for 2 h at 25 °C). The photogenerated holes and ·O₂⁻ were found to be main reactive species for the BzOH oxidation over BiOBr spheres by scavenging tests and spin-trapping EPR spectra. The higher photocatalytic activity of BiOBr-sMS was attributed to its more open hierarchical structure, efficient charge separation, more negative conduction-band position and the generation of larger amounts of ·O₂⁻. Full article

(This article belongs to the Special Issue Nanocatalysts for the Degradation of Refractory Pollutants)

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26 pages, 2539 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Machine Learning: A Suitable Method for Biocatalysis

by Pedro Sousa Sampaio and Pedro Fernandes

Catalysts 2023, 13(6), 961; https://doi.org/10.3390/catal13060961 - 1 Jun 2023

Cited by 12 | Viewed by 4482

Abstract

Biocatalysis is currently a workhorse used to produce a wide array of compounds, from bulk to fine chemicals, in a green and sustainable manner. The success of biocatalysis is largely thanks to an enlargement of the feasible chemical reaction toolbox. This materialized due [...] Read more.

Biocatalysis is currently a workhorse used to produce a wide array of compounds, from bulk to fine chemicals, in a green and sustainable manner. The success of biocatalysis is largely thanks to an enlargement of the feasible chemical reaction toolbox. This materialized due to major advances in enzyme screening tools and methods, together with high-throughput laboratory techniques for biocatalyst optimization through enzyme engineering. Therefore, enzyme-related knowledge has significantly increased. To handle the large number of data now available, computational approaches have been gaining relevance in biocatalysis, among them machine learning methods (MLMs). MLMs use data and algorithms to learn and improve from experience automatically. This review intends to briefly highlight the contribution of biocatalysis within biochemical engineering and bioprocesses and to present the key aspects of MLMs currently used within the scope of biocatalysis and related fields, mostly with readers non-skilled in MLMs in mind. Accordingly, a brief overview and the basic concepts underlying MLMs are presented. This is complemented with the basic steps to build a machine learning model and followed by insights into the types of algorithms used to intelligently analyse data, identify patterns and develop realistic applications in biochemical engineering and bioprocesses. Notwithstanding, and given the scope of this review, some recent illustrative examples of MLMs in protein engineering, enzyme production, biocatalyst formulation and enzyme screening are provided, and future developments are suggested. Overall, it is envisaged that the present review will provide insights into MLMs and how these are major assets for more efficient biocatalysis. Full article

(This article belongs to the Special Issue Editorial Board Member's Collection Series: Innovative Biocatalysts and Enzyme Immobilization)

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12 pages, 2573 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Improving the Stability of Ru-Doped Ni-Based Catalysts for Steam Methane Reforming during Daily Startup and Shutdown Operation

by Tae-Young Kim, Jong-Heon Lee, Seongbin Jo, Jueon Kim, Jin-Hyeok Woo, Ragupathy Dhanusuraman, Jae-Chang Kim and Soo-Chool Lee

Catalysts 2023, 13(6), 949; https://doi.org/10.3390/catal13060949 - 30 May 2023

Cited by 3 | Viewed by 1826

Abstract

In this study, a Ru-doped Ni pellet-type catalyst was prepared to produce hydrogen via steam methane reforming (SMR). A small amount of Ru addition on the Ni catalyst improved Ni dispersion, thus affording a higher catalytic activity than that of the Ni catalyst. [...] Read more.

In this study, a Ru-doped Ni pellet-type catalyst was prepared to produce hydrogen via steam methane reforming (SMR). A small amount of Ru addition on the Ni catalyst improved Ni dispersion, thus affording a higher catalytic activity than that of the Ni catalyst. During the daily startup and shutdown (DSS) operations, the CH₄ conversion of Ni catalysts significantly decreased because of Ni metal oxidation to NiAl₂O₄, which is not reduced completely at 700 °C. Conversely, the oxidized Ni species in the Ru–Ni catalyst can be reduced under SMR conditions because of H₂ spillover from the surface of Ru onto the surface of Ni. Consequently, the addition of a small quantity of Ru to the Ni catalyst can improve the catalytic activity and stability during the DSS operation. Full article

(This article belongs to the Special Issue Advances in Reforming Catalysts for Hydrogen Production)

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20 pages, 9564 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Enantioselective Catalytic Electrochemical Organic Transformations

by Fabrizio Medici, Simonetta Resta, Stefano Andolina and Maurizio Benaglia

Catalysts 2023, 13(6), 944; https://doi.org/10.3390/catal13060944 - 28 May 2023

Cited by 6 | Viewed by 2699

Abstract

Different approaches can be undertaken to realise a stereoselective electrochemical synthesis. Significant contributions to enantioselective electrochemical organic synthesis have been reported and largely reviewed in recent years. However, the development of general strategies for the electrochemical enantiocontrol of a transformation still presents considerable [...] Read more.

Different approaches can be undertaken to realise a stereoselective electrochemical synthesis. Significant contributions to enantioselective electrochemical organic synthesis have been reported and largely reviewed in recent years. However, the development of general strategies for the electrochemical enantiocontrol of a transformation still presents considerable challenges; in particular, relatively few contributions of highly enantioselective catalytic electrochemical reactions have been reported to date. In this review article, the most recent examples of asymmetric electrochemical catalysis are discussed. The article is organised by the three types of enantioselective catalysis: metal-based catalysis, organocatalysis and biocatalysis; in each section, the most significant and recent advances are presented and discussed. Full article

(This article belongs to the Special Issue New Trends in Asymmetric Catalysis: Green and Sustainable Catalysts)

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16 pages, 5219 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Cyclic Carbonates through the Photo-Induced Carboxylative Cyclization of Allylic Alcohol with CO₂: A Comprehensive Kinetic Study of the Reaction Mechanism by In Situ ATR-IR Spectroscopy

by Joseph Grondin, Christian Aupetit, Jean-Marc Vincent and Thierry Tassaing

Catalysts 2023, 13(6), 939; https://doi.org/10.3390/catal13060939 - 26 May 2023

Viewed by 1624

Abstract

A one-pot multicomponent green process is investigated for the synthesis of perfluoroalkylated cyclic carbonate which merges the photo-promoted Atom Transfer Radical Addition (ATRA) of a perfluoroalkyl iodide (Rf-I) onto allyl alcohols with the Lewis-base-promoted carboxylative cyclization. The evolution of the complex mixture during [...] Read more.

A one-pot multicomponent green process is investigated for the synthesis of perfluoroalkylated cyclic carbonate which merges the photo-promoted Atom Transfer Radical Addition (ATRA) of a perfluoroalkyl iodide (Rf-I) onto allyl alcohols with the Lewis-base-promoted carboxylative cyclization. The evolution of the complex mixture during the reaction was monitored by in situ ATR-IR and Raman spectroscopies that provided insights into the reaction mechanism. The effect on the kinetics and the carbonate yields of key parameters such as the stoichiometry of reagents, the nature of the Lewis base and the solvent, the temperature and the pressure were evaluated. It was found that high yields were obtained using strong Lewis bases that played both the role of activating the allyl alcohol for the generation of the allyl carbonate in the presence of CO₂ and promoting the ATRA reaction through the activation of C₄F₉I by halogen bonding. This protocol was also extended to various unsaturated alcohols. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Green Catalysts)

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15 pages, 10629 KiB

Open AccessEditor’s ChoiceArticle

Selective Hydrogenation of Adiponitrile to 6-Aminocapronitrile over Ni/α-Al₂O₃ Catalysts Doped with K₂O and La₂O₃

by Lei Zhao, Caiyun Wang, Jixiang Chen, Ziyang Nie, Jiyan Zhang and Xuebin Lu

Catalysts 2023, 13(6), 934; https://doi.org/10.3390/catal13060934 - 25 May 2023

Viewed by 1599

Abstract

A series of Ni/Al₂O₃, Ni/K₂O-Al₂O₃ and Ni/La₂O₃-K₂O-Al₂O₃ catalysts that possess high activities for partial hydrogenation of adiponitrile to 6-aminocapronitrile has been successfully synthesized by the [...] Read more.

A series of Ni/Al₂O₃, Ni/K₂O-Al₂O₃ and Ni/La₂O₃-K₂O-Al₂O₃ catalysts that possess high activities for partial hydrogenation of adiponitrile to 6-aminocapronitrile has been successfully synthesized by the impregnation method. The catalytic performance was investigated under atmospheric pressure and in the absence of ammonia and a significant enhancement in the activity after the introduction of potassium oxide and lanthana was observed. Aiming to study the influence of K₂O and La₂O₃ promoters on the physicochemical properties, we characterized the catalysts by N₂ adsorption/desorption, XRD, H₂-TPR, H₂-chemisorption, H₂-TPD and TEM techniques. A combination of XRD, TEM and H₂-chemisorption showed that Ni⁰ particles with a higher dispersion are obtained after the addition of La₂O₃. Compared with the Ni/Al₂O₃ catalyst, the Ni/La₂O₃-K₂O-Al₂O₃ catalyst with an appropriate amount of promoter enjoys a more catalyst surface alkalescence, enhances the electronic density of nickel and higher dispersion of nickel and exhibits higher activity and 6-aminocapronitrile selectivity than Ni/α-Al₂O₃ during the hydrogenation of adiponitrile in the absence of ammonia, i.e., K₂O and La₂O₃ improved the performance of the nickel-based catalyst. Full article

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11 pages, 4522 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Fabrication of New TiO₂ Photocatalyst for Removing Organic Dyes and Hazardous VOCs in Air Purifier System

by Ji Won Lee, Rak Hyun Jeong, Ikjo Shin and Jin-Hyo Boo

Catalysts 2023, 13(6), 935; https://doi.org/10.3390/catal13060935 - 25 May 2023

Viewed by 1522

Abstract

We synthesized an amorphous Ti-based hydroperoxo complex (ATPC) using a facile method involvingonly titanium hydride (TiH₂) and H₂O₂ under mild conditions. We chose TiH₂ as the precursor because it has more reactive sites than metal oxides such [...] Read more.

We synthesized an amorphous Ti-based hydroperoxo complex (ATPC) using a facile method involvingonly titanium hydride (TiH₂) and H₂O₂ under mild conditions. We chose TiH₂ as the precursor because it has more reactive sites than metal oxides such as TiO₂. Qualitative and quantitative optical measurements showed that our synthesized ATPC photocatalysts contained many hydroperoxo groups and various oxidation states of Ti (Ti²⁺, Ti³⁺, and Ti⁴⁺). Thus, the synthesized ATPC exhibits excellent photocatalytic properties with very fast rates of organic decolorization compared to other conventional visiblelight catalysts. The presence of many hydroperoxo complexes increases the formation of active radicals, which can degrade VOCs such as acetaldehyde in a gas phase. To test the application of the synthesized ATPC, we fabricated a filter system in an air purifier using ATPC coating layers and successfully removed the VOCs. We also proposed a possible photocatalytic oxidation mechanism with ATPC based on this study. It is important to conduct application tests as well as commercialization in photocatalytic experiments. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Catalytic Materials")

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14 pages, 4548 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Efficient and Stable Ni/SBA-15 Catalyst for Dry Reforming of Methane: Effect of Citric Acid Concentration

by Mamoona Waris, Howon Ra, Sungmin Yoon, Min-Jae Kim and Kyubock Lee

Catalysts 2023, 13(6), 916; https://doi.org/10.3390/catal13060916 - 23 May 2023

Cited by 5 | Viewed by 2188

Abstract

Citric acid, one of the representative chelate compounds, has been widely used as an additive to achieve the highly dispersed metal-supported catalysts. This study aimed to investigate the effect of citric acid concentration on the preparation of the highly dispersed Ni catalysts on [...] Read more.

Citric acid, one of the representative chelate compounds, has been widely used as an additive to achieve the highly dispersed metal-supported catalysts. This study aimed to investigate the effect of citric acid concentration on the preparation of the highly dispersed Ni catalysts on mesoporous silica (SBA-15) for the dry reforming of methane. A series of Ni/SBA-15 catalysts with citric acid were prepared using the acid-assisted incipient wetness impregnation method, and the Ni/SBA-15 catalyst as a reference was synthesized via the impregnation method. First of all, the citric acid addition during the catalyst synthesis step regardless of its concentration resulted in highly dispersed Ni particles of ~4–7 nm in size in Ni/SBA-15 catalysts, which had a superior and stable catalytic performance in the dry reforming of methane (93% of CO₂ conversion and 86% of CH₄ conversion). In addition, the amount of coke formation was much lower in a series of Ni/SBA-15 catalysts with citric acid (~2–5 mg_coke g_cat⁻¹ h⁻¹) compared to pristine Ni/SBA-15 catalysts (~22 mg_coke g_cat⁻¹ h⁻¹). However, when the concentration of citric acid became higher, the more free NiO species that formed on the SBA-15 support, leading to large Ni particles after the stability test. The addition of citric acid is a very clear strategy for making highly dispersed catalysts, but its concentration needs to be carefully controlled. Full article

(This article belongs to the Special Issue State-of-the-Art of Catalytical Technology in Korea)

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12 pages, 2991 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Removal of Hexamethyldisiloxane by NaOH–Activated Porous Carbons Produced from Coconut Shells

by Siqi Lv, Xiaolong Ma, Qingling Fu, Yanhui Zheng and Zichuan Ma

Catalysts 2023, 13(6), 918; https://doi.org/10.3390/catal13060918 - 23 May 2023

Cited by 3 | Viewed by 1519

Abstract

The utilisation of activated porous carbon (APC) for the removal of volatile methyl siloxane (VMS) has attracted significant research attention. However, the development of materials with high adsorption capacity remains a challenge. In this study, we successfully developed a high-specific-surface-area (2551 m² [...] Read more.

The utilisation of activated porous carbon (APC) for the removal of volatile methyl siloxane (VMS) has attracted significant research attention. However, the development of materials with high adsorption capacity remains a challenge. In this study, we successfully developed a high-specific-surface-area (2551 m² g⁻¹) APC material with a large porous texture (1.30 cm³ g⁻¹) using coconut shell waste and NaOH as the activating agent. The performance of the APC material in the removal of hexamethyldisiloxane (L2) was evaluated using a fixed-bed dynamic adsorption setup. Notably, at 0 °C, the APC demonstrated a remarkable L2 removal ability, achieving a breakthrough adsorption capacity of 898.6 mg g⁻¹. By increasing the inlet concentration of L2 and decreasing the temperature appropriately, the L2 adsorption capacity could be further improved. One advantage of APCs is their simple recycling process, which allows for sustained adsorption performance even after five consecutive cycles of adsorption and desorption. Therefore, the prepared APC material holds great promise as an efficient adsorbent for the removal of VMS. Full article

(This article belongs to the Special Issue Environmental Catalysis/Adsorption for Organic Waste Resource Disposal)

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19 pages, 4869 KiB

Open AccessEditor’s ChoiceArticle

Metallic Supported Pd-Ag Membranes for Simultaneous Ammonia Decomposition and H₂ Separation in a Membrane Reactor: Experimental Proof of Concept

by Valentina Cechetto, Serena Agnolin, Luca Di Felice, Alfredo Pacheco Tanaka, Margot Llosa Tanco and Fausto Gallucci

Catalysts 2023, 13(6), 920; https://doi.org/10.3390/catal13060920 - 23 May 2023

Cited by 9 | Viewed by 2850

Abstract

The use of ammonia as a hydrogen carrier requires efficient cracking technology. A promising solution is the use of a membrane reactor (MR), which enables both ammonia decomposition and hydrogen separation to take place within the same device, providing advantages in terms of [...] Read more.

The use of ammonia as a hydrogen carrier requires efficient cracking technology. A promising solution is the use of a membrane reactor (MR), which enables both ammonia decomposition and hydrogen separation to take place within the same device, providing advantages in terms of efficiency and compactness compared to conventional systems. The literature reports that ceramic-supported double-skinned Pd-Ag membranes show outstanding performance for hydrogen separation as well as good stability of the separation layer during ammonia decomposition. However, their sealing in the reactor may result in leakage increase, while their mechanical stability remains an unresolved issue. To circumvent these limitations, the use of metallic supported Pd-based membranes is recommended, due to their higher mechanical stability and ease of sealing and integration in the reactor. In this work, we propose the development of robust metallic supported hydrogen-selective membranes for integration in membrane reactors for ammonia cracking. A conventional Pd-Ag membrane was prepared on a low-cost porous Hastelloy X tubular filter, modified with α-Al₂O₃/γ-Al₂O₃ to reach the desired surface quality. The membrane was then tested for ammonia decomposition in a MR configuration, showing the ability to reach >99% NH₃ conversion above 475 °C with H₂ feed recovery >60%. The results achieved pave the way towards a possible substitute for the ceramic-supported alternatives. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Catalytic and Photocatalytic Membrane Reactors)

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15 pages, 2344 KiB

Open AccessEditor’s ChoiceArticle

Electrochemical Characterisation of the Photoanode Containing TiO₂ and SnS₂ in the Presence of Various Pharmaceuticals

by Gabrijela Radić, Klara Perović, Tayebeh Sharifi, Hrvoje Kušić, Marin Kovačić and Marijana Kraljić Roković

Catalysts 2023, 13(5), 909; https://doi.org/10.3390/catal13050909 - 20 May 2023

Cited by 3 | Viewed by 1994

Abstract

In this work, the behaviour of photoanodes made of TiO₂, SnS₂ and TiO₂/SnS₂ was examined in the presence and absence of pharmaceuticals diclofenac (DCF), memantine hydrochloride (MEM) and salicylic acid (SA). The focus of the current research [...] Read more.

In this work, the behaviour of photoanodes made of TiO₂, SnS₂ and TiO₂/SnS₂ was examined in the presence and absence of pharmaceuticals diclofenac (DCF), memantine hydrochloride (MEM) and salicylic acid (SA). The focus of the current research is on the following photoelectrochemical (PEC) characterisation methods: linear polarisation, electrochemical impedance spectroscopy (EIS), and open circuit potential (OCP) monitoring. Linear polarisation and EIS provided useful information about the interaction between the pharmaceuticals and the photocatalytic materials. The presence of the selected pharmaceuticals affects the OCP value, mainly due to the pH change. The results obtained by PEC characterisation were compared to the photocatalytic (PC) efficiency of pharmaceutical degradation. In addition to the photocurrent response, the linear voltammogram indicates the electrochemical oxidation of DCF and SA. Geometry optimizations using density functional theory (DFT) showed that the HOMO orbitals’ position of DCF and SA are above the position of the TiO₂ HOMO level and below the position of the SnS₂ HOMO level. Due to this, the characteristic current peak for DCF and SA was registered, but only for TiO₂ and TiO₂/SnS₂ photoanodes. The oxidation current peak was not registered for MEM, although h⁺ scavenging properties were noticed for TiO₂ in the presence of MEM. Apparently, this is an interplay between the protonated and non-protonated forms of MEM and the differences in their HOMO positions. Full article

(This article belongs to the Special Issue Advances in Photocatalytic Wastewater Purification, 2nd Edition)

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19 pages, 4320 KiB

Open AccessEditor’s ChoiceArticle

Novel Control System Strategy for the Catalytic Oxidation of VOCs with Heat Recovery

by Angel Federico Miranda, María Laura Rodríguez, Federico Martin Serra and Daniel Oscar Borio

Catalysts 2023, 13(5), 897; https://doi.org/10.3390/catal13050897 - 16 May 2023

Cited by 1 | Viewed by 1480

Abstract

A theoretical study of the dynamic closed-loop behaviour of a reactor/feed-effluent heat exchanger (FEHE)/furnace system for the catalytic combustion of volatile organic compounds (VOCs) is presented. A 1D pseudohomogeneous plug-flow model is proposed to simulate the non-steady-state operation of the monolith reactor and [...] Read more.

A theoretical study of the dynamic closed-loop behaviour of a reactor/feed-effluent heat exchanger (FEHE)/furnace system for the catalytic combustion of volatile organic compounds (VOCs) is presented. A 1D pseudohomogeneous plug-flow model is proposed to simulate the non-steady-state operation of the monolith reactor and the FEHE, while the furnace behaviour is described by means of a heterogeneous model of lumped parameters. Positive energy feedback is a source of instability that leads to strong thermal oscillations (limit cycles) and may cause damage to the equipment and sintering of the catalyst. The design of a robust and flexible control system and an efficient control strategy are, therefore, required to ensure safe and stable operation. The response of the system under three different control strategies to the most frequent disturbance variables—the feed flowrate (F_V₀) and feed concentration of VOCs (C_0Et)—was evaluated. One of the control strategies consisted of a single-loop feedback system with servomechanism changes in the reactor inlet temperature (T₀) that manipulated the bypass valve and, sequentially, the natural gas flowrate in the furnace (F_NG). This approach made it possible to meet the control objective (reducing VOCs) without losing controllability and while minimizing the use of external fuel. Full article

(This article belongs to the Special Issue Catalysts for Air Pollution Control: Present and Future)

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12 pages, 3002 KiB

Open AccessEditor’s ChoiceArticle

Support Effect of Ga-Based Catalysts in the CO₂-Assisted Oxidative Dehydrogenation of Propane

by Wei Zhou, Yulin Jiang, Zhiguo Sun, Shiqi Zhou, Erpai Xing, Yang Hai, Guanghao Chen and Yuetong Zhao

Catalysts 2023, 13(5), 896; https://doi.org/10.3390/catal13050896 - 16 May 2023

Cited by 6 | Viewed by 2315

Abstract

Carbon dioxide (CO₂) assisted oxidative dehydrogenation of propane over Ga-modified catalysts is highly sensitive to the identity of support, but the underlying cause of support effects has not been well established. In this article, SSZ-13, SSZ-39, ZSM-5, silica and γ-Al₂ [...] Read more.

Carbon dioxide (CO₂) assisted oxidative dehydrogenation of propane over Ga-modified catalysts is highly sensitive to the identity of support, but the underlying cause of support effects has not been well established. In this article, SSZ-13, SSZ-39, ZSM-5, silica and γ-Al₂O₃ were used to load Ga species by incipient wet impregnation. The structure, textural properties, acidity of the Ga-based catalysts and the process of CO₂-assisted oxidative dehydrogenation of propane were examined by X-ray diffraction (XRD), nitrogen physisorption (N₂ physisorption), ammonia temperature-programmed desorption (NH₃-TPD), pyridine chemisorbed Fourier transform infrared spectra (Py-FTIR), OH-FTIR and in situ FTIR. Evaluation of the catalytic performance combined with detailed catalyst characterization suggests that their dehydrogenation activity is positively associated with the number of acid sites in middle strength, confirming that the Lewis acid sites generated by Ga cations are the active species in the reaction. Ga/Na-SSZ-39(9) also has feasible acidic strength and a unique channel structure, which is conducive to the dissociative adsorption of propane and desorption of olefins. The Ga/Na-SSZ-39(9) catalysts showed superior olefins selectivity and catalytic stability at 600 ℃ compared to any other catalysts. This approach to quantifying support acid strength, and channel structure and applying it as a key catalytic descriptor of support effects is a useful tool to enable the rational design of next-generation CO₂-assisted oxidative dehydrogenation catalysts. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Clean Energy Production and Carbon Dioxide Utilization)

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11 pages, 1780 KiB

Open AccessEditor’s ChoiceArticle

Rational Design of Cyclodextrin Glycosyltransferase with Improved Hesperidin Glycosylation Activity

by Hanchi Chen, Jiajun Wang, Yi Liu, Yongfan Chen, Chunfeng Wang, Linjiang Zhu, Yuele Lu and Xiaolong Chen

Catalysts 2023, 13(5), 885; https://doi.org/10.3390/catal13050885 - 14 May 2023

Cited by 3 | Viewed by 1764

Abstract

Cyclodextrin glycosyltransferase (CGTase) can catalyze the glycosylation of hesperidin, resulting in α-glycosyl hesperidin with significantly improved water solubility. In this study, a rational design of CGTase to improve its hesperidin glycosylation activity was investigated. The strategy we employed involved docking hesperidin in its [...] Read more.

Cyclodextrin glycosyltransferase (CGTase) can catalyze the glycosylation of hesperidin, resulting in α-glycosyl hesperidin with significantly improved water solubility. In this study, a rational design of CGTase to improve its hesperidin glycosylation activity was investigated. The strategy we employed involved docking hesperidin in its near-attack conformation and virtually mutating the surrounding residues, followed by calculating the changes in binding energy using Rosetta flex-ddG. The mutations with a stabilization effect were then subjected to an activity assay. Starting from CGTase-Y217F, we obtained three double-point mutants, Y217F/M351F, Y217F/M351L, and Y217F/D393H, with improved hesperidin glycosylation activities after screening twenty variants. The best variant, Y217F/D393H, exhibited a catalytic activity of 1305 U/g, and its kcat/KmA is 2.36 times higher compared to CGTase-Y217F and 15.14 times higher compared to the wild-type CGTase. Molecular dynamic simulations indicated that hesperidin was repulsed by CGTase-Y217F when bound in a near-attack conformation. However, by introducing a second-point mutation with a stabilization effect, the repulsion effect is weakened, resulting in a reduction in the distances between the bond-forming atoms and, thus, favoring the reaction. Full article

(This article belongs to the Special Issue High-Throughput Computational Design of Catalysts)

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