Catalysts

17 pages, 3487 KiB

Open AccessFeature PaperArticle

The Formation of Mn-Ce-Zr Oxide Catalysts for CO and Propane Oxidation: The Role of Element Content Ratio

by Tatyana N. Afonasenko, Daria V. Yurpalova, Zakhar S. Vinokurov, Andrey A. Saraev, Egor E. Aidakov, Valeriya P. Konovalova, Vladimir A. Rogov and Olga A. Bulavchenko

Catalysts 2023, 13(1), 211; https://doi.org/10.3390/catal13010211 - 16 Jan 2023

Cited by 5 | Viewed by 1675

Abstract

The MnO_х-ZrO₂-CeO₂ oxide catalysts were synthesized by co-precipitation method with varying (1) Zr/Zr + Ce molar ratio at constant manganese content of 0.3; (2) manganese content at constant Zr/Ce molar ratio of 1; (3) Mn/Mn + Zr molar [...] Read more.

The MnO_х-ZrO₂-CeO₂ oxide catalysts were synthesized by co-precipitation method with varying (1) Zr/Zr + Ce molar ratio at constant manganese content of 0.3; (2) manganese content at constant Zr/Ce molar ratio of 1; (3) Mn/Mn + Zr molar ratio at constant Ce content of 0.5. Catalysts are characterized by XRD, N₂ adsorption, TPR, and XPS. The catalytic activity of all the series was tested in the CO and propane oxidation reactions. In contrast to the variation of the manganese content, the Zr/Zr + Ce molar ratio does not significantly affect the catalytic properties. The dependence of the catalytic activity in CO oxidation on the manganese content has a «volcano» shape, and the best catalytic performance is exhibited by the catalyst with Mn/(Zr + Ce) = 1. In the case of propane oxidation reaction, there is «sigma» like dependence, activity increases with increase of Mn/(Mn + Zr + Ce) molar ratio up to 0.3, stabilizing with a further increase in the manganese content. XRD and XPS have shown that with an increase of the Mn concentration in the MnO_x-ZrO₂-CeO₂ catalysts, the amount of crystalline manganese oxides such as Mn₂O₃ and Mn₃O₄, as well as the surface concentration of Mn cations, increases. While the content of Mn_xZr_yCe_1-x-yO₂ solid solution decreases, the concentration of manganese cations (x) in volume of Mn_xZr_yCe_1-x-yO₂ mixed oxide grows. The maximum activity in CO oxidation corresponds to the balance between the amount of the solid solution and the concentration of manganese cations in the volume of mixed oxide. The propane oxidation reaction is less sensitive to the state of manganese ion rather than to its amount. In this case, a decrease in the content of the Mn_xZr_yCe_1-x-yO₂ solid solution with increase in manganese amount in catalyst is compensated by an increase in content of crystalline manganese oxides and the surface concentration of manganese. Full article

(This article belongs to the Special Issue Functional Materials for Application in Adsorption & Catalysis)

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64 pages, 21660 KiB

Open AccessReview

Palladium Supported on Bioinspired Materials as Catalysts for C–C Coupling Reactions

by Gianluigi Albano, Antonella Petri and Laura Antonella Aronica

Catalysts 2023, 13(1), 210; https://doi.org/10.3390/catal13010210 - 16 Jan 2023

Cited by 5 | Viewed by 2129

Abstract

In recent years, the immobilization of palladium nanoparticles on solid supports to prepare active and stable catalytic systems has been deeply investigated. Compared to inorganic materials, naturally occurring organic solids are inexpensive, available and abundant. Moreover, the surface of these solids is fully [...] Read more.

In recent years, the immobilization of palladium nanoparticles on solid supports to prepare active and stable catalytic systems has been deeply investigated. Compared to inorganic materials, naturally occurring organic solids are inexpensive, available and abundant. Moreover, the surface of these solids is fully covered by chelating groups which can stabilize the metal nanoparticles. In the present review, we have focused our attention on natural biomaterials-supported metal catalysts applied to the formation of C–C bonds by Mizoroki–Heck, Suzuki–Miyaura and Sonogashira reactions. A systematic approach based on the nature of the organic matrix will be followed: (i) metal catalysts supported on cellulose; (ii) metal catalysts supported on starch; (iii) metal catalysts supported on pectin; (iv) metal catalysts supported on agarose; (v) metal catalysts supported on chitosan; (vi) metal catalysts supported on proteins and enzymes. We will emphasize the effective heterogeneity and recyclability of each catalyst, specifying which studies were carried out to evaluate these aspects. Full article

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

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16 pages, 17517 KiB

Open AccessArticle

Diastereo- and Enantioselective Synthesis of Highly Functionalized Tetrahydropyridines by Recyclable Novel Bifunctional C₂-Symmetric Ionic Liquid–Supported (S)-Proline Organocatalyst

by Prabhakara Madivalappa Davanagere, Mrinmoy De, Kaushik Chanda and Barnali Maiti

Catalysts 2023, 13(1), 209; https://doi.org/10.3390/catal13010209 - 16 Jan 2023

Cited by 4 | Viewed by 1657

Abstract

An efficient, novel bifunctional C₂-symmetric ionic liquid–supported (S)-proline organocatalyst 7 was developed for a one-pot, five-component reaction involving β-keto esters 8, aryl aldehydes 9, and aryl amines 10, affording highly functionalized tetrahydropyridines 11a–o by simultaneous [...] Read more.

An efficient, novel bifunctional C₂-symmetric ionic liquid–supported (S)-proline organocatalyst 7 was developed for a one-pot, five-component reaction involving β-keto esters 8, aryl aldehydes 9, and aryl amines 10, affording highly functionalized tetrahydropyridines 11a–o by simultaneous generation of fives bonds and two stereogenic centers with extraordinary diastereo- and enantioselectivities (up to >99:1 dr, 95:5 er) in isopropanol with high yields (up to 92%). This protocol provides quick access to diverse enantio-enriched, highly functionalized diastereo- and enantioselective tetrahydropyridines in a green medium without any column chromatographic purification. The catalyst was recycled five times without significant loss of its catalytic activity. Full article

(This article belongs to the Special Issue Advances in Asymmetric Organocatalytic Reactions)

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18 pages, 3231 KiB

Open AccessArticle

Xanthan Gum-Mediated Silver Nanoparticles for Ultrasensitive Electrochemical Detection of Hg²⁺ Ions from Water

by Sadia Shakeel, Farah Naz Talpur, Sirajuddin, Nadia Anwar, Muhammad Aamir Iqbal, Adnan Ibrahim, Hassan Imran Afridi, Ahsanullah Unar, Awais Khalid, Inas A. Ahmed, Wen-Cheng Lai and Muhammad Sohail Bashir

Catalysts 2023, 13(1), 208; https://doi.org/10.3390/catal13010208 - 16 Jan 2023

Cited by 5 | Viewed by 2475

Abstract

An environmentally safe, efficient, and economical microwave-assisted technique was selected for the production of silver nanoparticles (AgNPs). To prepare uniformly disseminated AgNPs, xanthan gum (XG) was utilized as both a reducing and capping agent. UV–Vis spectroscopy was used to characterize the formed XG-AgNPs, [...] Read more.

An environmentally safe, efficient, and economical microwave-assisted technique was selected for the production of silver nanoparticles (AgNPs). To prepare uniformly disseminated AgNPs, xanthan gum (XG) was utilized as both a reducing and capping agent. UV–Vis spectroscopy was used to characterize the formed XG-AgNPs, with the absorption band regulated at 414 nm under optimized parameters. Atomic force microscopy was used to reveal the size and shape of XG-AgNPs. The interactions between the XG capping agent and AgNPs observed using Fourier transform infrared spectroscopy. The XG-AgNPs were placed in between glassy carbon electrode and Nafion^® surfaces and then deployed as sensors for voltammetric evaluation of mercury ions (Hg²⁺) using square-wave voltammetry as an analytical mode. Required Nafion^® quantities, electrode behavior, electrolyte characteristics, pH, initial potentials, accumulation potentials, and accumulation durations were all comprehensively investigated. In addition, an electrochemical mechanism for the oxidation of Hg²⁺ was postulated. With an exceptional limit of detection of 0.18 ppb and an R² value of 0.981, the sensors’ measured linear response range was 0.0007–0.002 µM Hg²⁺. Hg²⁺ evaluations were ultimately unaffected by the presence of many coexisting metal ions (Cd²⁺, Pb²⁺, Cr₂O₄, Co²⁺,Cu²⁺, CuSO₄). Spiked water samples were tested using the described approach, with Hg²⁺ recoveries ranging from 97% to 100%. Full article

(This article belongs to the Special Issue Nanoparticles in the Catalysis)

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3 pages, 171 KiB

Open AccessEditorial

Photoactive Materials for the Catalytic Decomposition of Water Pollutants

by Beata Krasnodębska-Ostręga and Krzysztof Miecznikowski

Catalysts 2023, 13(1), 207; https://doi.org/10.3390/catal13010207 - 16 Jan 2023

Viewed by 928

Abstract

The use of UV and Vis light (in the form of solar energy) in the presence of semiconductor nanostructured materials as photocatalysts is effective for the adequate removal of a wide spectrum of pollutants (resistant to other degradation techniques) in various types of [...] Read more.

The use of UV and Vis light (in the form of solar energy) in the presence of semiconductor nanostructured materials as photocatalysts is effective for the adequate removal of a wide spectrum of pollutants (resistant to other degradation techniques) in various types of wastewater, which are important elements of the development of science related to photocatalysis [...] Full article

(This article belongs to the Special Issue Photoactive Materials for the Catalytic Decomposition of Water Pollutants)

18 pages, 2162 KiB

Open AccessArticle

Discovery and Heterologous Expression of Unspecific Peroxygenases

by Katharina Ebner, Lukas J. Pfeifenberger, Claudia Rinnofner, Veronika Schusterbauer, Anton Glieder and Margit Winkler

Catalysts 2023, 13(1), 206; https://doi.org/10.3390/catal13010206 - 16 Jan 2023

Cited by 11 | Viewed by 3411

Abstract

Since 2004, unspecific peroxygenases, in short UPOs (EC. 1.11.2.1), have been explored. UPOs are closing a gap between P450 monooxygenases and chloroperoxidases. These enzymes are highly active biocatalysts for the selective oxyfunctionalisation of C–H, C=C and C-C bonds. UPOs are secreted fungal proteins [...] Read more.

Since 2004, unspecific peroxygenases, in short UPOs (EC. 1.11.2.1), have been explored. UPOs are closing a gap between P450 monooxygenases and chloroperoxidases. These enzymes are highly active biocatalysts for the selective oxyfunctionalisation of C–H, C=C and C-C bonds. UPOs are secreted fungal proteins and Komagataella phaffii (Pichia pastoris) is an ideal host for high throughput screening approaches and UPO production. Heterologous overexpression of 26 new UPOs by K. phaffii was performed in deep well plate cultivation and shake flask cultivation up to 50 mL volume. Enzymes were screened using colorimetric assays with 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,6-dimethoxyphenol (DMP), naphthalene and 5-nitro-1,3-benzodioxole (NBD) as reporter substrates. The PaDa-I (AaeUPO mutant) and HspUPO were used as benchmarks to find interesting new enzymes with complementary activity profiles as well as good producing strains. Herein we show that six UPOs from Psathyrella aberdarensis, Coprinopsis marcescibilis, Aspergillus novoparasiticus, Dendrothele bispora and Aspergillus brasiliensis are particularly active. Full article

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

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19 pages, 3536 KiB

Open AccessArticle

Effect of Modulation and Functionalization of UiO-66 Type MOFs on Their Surface Thermodynamic Properties and Lewis Acid–Base Behavior

by Ali Ali-Ahmad, Tayssir Hamieh, Thibault Roques-Carmes, Mohamad Hmadeh and Joumana Toufaily

Catalysts 2023, 13(1), 205; https://doi.org/10.3390/catal13010205 - 16 Jan 2023

Cited by 2 | Viewed by 2166

Abstract

In this study, we investigated the surface thermodynamic properties of four MOF structures of the UiO-66 series, by employing seven molecular models, a thermal model, and three other methods using the inverse gas chromatography (IGC) technique at infinite dilution. We first determined the [...] Read more.

In this study, we investigated the surface thermodynamic properties of four MOF structures of the UiO-66 series, by employing seven molecular models, a thermal model, and three other methods using the inverse gas chromatography (IGC) technique at infinite dilution. We first determined the effect of the modulation of UiO-66 by an acid (e.g., formic acid and acetic acid) and on the other hand, we studied the effect of the functionalization of the organic linker by an amine group (NH₂) on their dispersive component of the surface energy and on their Lewis acid–base properties. We found that all the studied MOFs presented an amphoteric character with a strong acidity whose acidity/basicity ratio is greater than 1 using all the models and methods in IGC. Moreover, the introduction of a modulator such as acetic acid or formic acid in the synthesis of these MOFs increased the number of structural defects and therefore increased the acidity of these MOFs. Similarly, the functionalization of the MOF by the NH₂ group leads to an increase in the basicity constant of the functionalized MOF while remaining smaller than their acidity constant. In addition, the use of acids as modulators and amine groups as functional groups resulted in an increase in the dispersive component of the surface energy of the MOFs. Finally, comparing the results obtained by the different models and methods and based on the increasing order of the acidity of each MOF, it was clear that the thermal model resulted in more exact and precise values than the others. Our findings pave the way for the design and development of new acid catalysts based on UiO-66 structures. Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes, 2nd Edition)

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28 pages, 52853 KiB

Open AccessReview

State-of-the-Art Review of Oxidative Dehydrogenation of Ethane to Ethylene over MoVNbTeO_x Catalysts

by Yuxin Chen, Binhang Yan and Yi Cheng

Catalysts 2023, 13(1), 204; https://doi.org/10.3390/catal13010204 - 16 Jan 2023

Cited by 9 | Viewed by 3469

Abstract

Ethylene is mainly produced by steam cracking of naphtha or light alkanes in the current petrochemical industry. However, the high-temperature operation results in high energy demands, high cost of gas separation, and huge CO₂ emissions. With the growth of the verified shale [...] Read more.

Ethylene is mainly produced by steam cracking of naphtha or light alkanes in the current petrochemical industry. However, the high-temperature operation results in high energy demands, high cost of gas separation, and huge CO₂ emissions. With the growth of the verified shale gas reserves, oxidative dehydrogenation of ethane (ODHE) becomes a promising process to convert ethane from underutilized shale gas reserves to ethylene at a moderate reaction temperature. Among the catalysts for ODHE, MoVNbTeO_x mixed oxide has exhibited superior catalytic performance in terms of ethane conversion, ethylene selectivity, and/or yield. Accordingly, the process design is compact, and the economic evaluation is more favorable in comparison to the mature steam cracking processes. This paper aims to provide a state-of-the-art review on the application of MoVNbTeO_x catalysts in the ODHE process, involving the origin of MoVNbTeO_x, (post-) treatment of the catalyst, material characterization, reaction mechanism, and evaluation as well as the reactor design, providing a comprehensive overview of M1 MoVNbTeO_x catalysts for the oxidative dehydrogenation of ethane, thus contributing to the understanding and development of the ODHE process based on MoVNbTeO_x catalysts. Full article

(This article belongs to the Special Issue 10th Anniversary of Catalysts: Feature Papers in Catalytic Reaction Engineering)

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26 pages, 12759 KiB

Open AccessArticle

Novel Highly Efficient Green and Reusable Cu(II)/Chitosan-Based Catalysts for the Sonogashira, Buchwald, Aldol, and Dipolar Cycloaddition Reactions

by Artem P. Dysin, Anton R. Egorov, Omar Khubiev, Roman Golubev, Anatoly A. Kirichuk, Victor N. Khrustalev, Nikolai N. Lobanov, Vasili V. Rubanik, Alexander G. Tskhovrebov and Andreii S. Kritchenkov

Catalysts 2023, 13(1), 203; https://doi.org/10.3390/catal13010203 - 15 Jan 2023

Cited by 2 | Viewed by 2258

Abstract

In this study, new Cu(II)/chitosan-based systems were designed via (i) the treatment of chitosan with sodium sulfate (1a) or sodium acetate (1b); (ii) the coating of 1a or 2a with a sodium hyaluronate layer (2a and 2b, [...] Read more.

In this study, new Cu(II)/chitosan-based systems were designed via (i) the treatment of chitosan with sodium sulfate (1a) or sodium acetate (1b); (ii) the coating of 1a or 2a with a sodium hyaluronate layer (2a and 2b, correspondingly); (iii) the treatment of a cholesterol–chitosan conjugate with sodium sulfate (3a) or sodium acetate (3b); and (iv) the succination of 1a and 1b to afford 4a and 4b or the succination of 2a and 2b to yield 5a and 5b. The catalytic properties of the elaborated systems in various organic transformations were evaluated. The use of copper sulfate as the source of Cu²⁺ ions results in the formation of nanoparticles, while the use of copper acetate leads to the generation of conventional coarse-grained powder. Cholesterol-containing systems have proven to be highly efficient catalysts for the cross-coupling reactions of different types (e.g., Sonogashira, Buchwald–Hartwig, and Chan–Lam types); succinated systems coated with a layer of hyaluronic acid are promising catalysts for the aldol reaction; systems containing inorganic copper(II) salt nanoparticles are capable of catalyzing the nitrile-oxide-to-nitrile 1,3-dipolar cycloaddition. The elaborated catalytic systems efficiently catalyze the aforementioned reactions in the greenest solvent available, i.e., water, and the processes could be conducted in air. The studied catalytic reactions proceed selectively, and the isolation of the product does not require column chromatography. The product is separated from the catalyst by simple filtration or centrifugation. Full article

(This article belongs to the Special Issue Catalysis in Green Chemistry and Organic Synthesis)

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9 pages, 2286 KiB

Open AccessEditor’s ChoiceCommunication

High-Temperature-Treated LTX Zeolites as Heterogeneous Catalysts for the Hock Cleavage

by Jan Drönner, Karim Bijerch, Peter Hausoul, Regina Palkovits and Matthias Eisenacher

Catalysts 2023, 13(1), 202; https://doi.org/10.3390/catal13010202 - 15 Jan 2023

Cited by 1 | Viewed by 1843

Abstract

Hydroxybenzene, commonly known as phenol, is one of the most important organic commodity chemicals. To produce phenol, the cumene process is the most used process worldwide. A crucial step in this process is the Hock rearrangement, which has a major impact on the [...] Read more.

Hydroxybenzene, commonly known as phenol, is one of the most important organic commodity chemicals. To produce phenol, the cumene process is the most used process worldwide. A crucial step in this process is the Hock rearrangement, which has a major impact on the overall cumene consumption rate and determines the safety level of the process. The most used catalyst for the cleavage of cumene hydroperoxide (CHP) is sulfuric acid. Besides its strong corrosive property, which increases plant investment costs, it also requires neutralization after the decomposition step to prevent side reactions. In this study, we show that high-temperature-treated Linde Type X (LTX) zeolites exhibit a high activity for the peroxide cleavage step. In addition, the structure–activity relationship responsible for this good performance in the reaction system of the HOCK rearrangement was investigated. XRPD analyses revealed the formation of a new phase after temperature treatment above 900 °C. The Si/Al ratio determined by EDX suggested the formation of extra-framework aluminum, which was confirmed by solid-state NMR analysis. The newly formed extra-framework aluminum was found to be responsible for the high catalytic activity. BET analyses showed that the surface area drops at higher calcination temperatures. This leads to a lower catalytic activity for most known reactions. However, for this study, no decrease in activity has been observed. The newfound material shows extraordinarily high activity as a catalyst in the HOCK cleavage and has the potential to be a heterogeneous alternative to sulfuric acid for this reaction. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis in Green Chemistry II)

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10 pages, 6865 KiB

Open AccessArticle

Fabrication and Photocatalytic Activity of Single Crystalline TiO₂ Hierarchically Structured Microspheres

by Haisheng Huang, Qi Kong, Xin Yue, Kunlei Wang, Zhishun Wei and Ying Chang

Catalysts 2023, 13(1), 201; https://doi.org/10.3390/catal13010201 - 15 Jan 2023

Cited by 1 | Viewed by 1185

Abstract

Single crystalline anatase TiO₂ microspheres with co-exposed {001}/{101} facets were prepared by a facile one-pot hydrothermal method using NaF as a morphology controlling agent. The influences of the NaF amount on the morphology and also on the photocatalytic activity were investigated systematically. [...] Read more.

Single crystalline anatase TiO₂ microspheres with co-exposed {001}/{101} facets were prepared by a facile one-pot hydrothermal method using NaF as a morphology controlling agent. The influences of the NaF amount on the morphology and also on the photocatalytic activity were investigated systematically. The obtained microspheres possessed better morphology when the concentration of NaF was chosen at 0.1 mol/L, and the experimental results indicated that the crystal structure and morphology played important roles on the photocatalytic activity, based on the experimental results it was found that the photocatalytic degradation efficiency of TiO₂ microspheres on Tetracycline hydrochloride could reach 76.4% in 2 h. Finally, a growth mechanism was proposed by investigating the growth process, i.e., a synergistic effect of F ions modified Ostwald ripening and oriented attachment. Full article

(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)

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16 pages, 726 KiB

Open AccessFeature PaperReview

Anticancer Asparaginases: Perspectives in Using Filamentous Fungi as Cell Factories

by Pedro Henrique Dias Garcia, Tales Alexandre Costa-Silva, Martí Morera Gómez, Fabiano Jares Contesini, Paula Renata Bueno Campos Canella and Patrícia de Oliveira Carvalho

Catalysts 2023, 13(1), 200; https://doi.org/10.3390/catal13010200 - 15 Jan 2023

Cited by 2 | Viewed by 2254

Abstract

The enzyme L-asparaginase (L-asparagine amidohydrolase) catalyzes the breakdown of L-asparagine into aspartate and ammonia, which leads to an anti-neoplastic activity stemming from its capacity to deplete L-asparagine concentrations in the bloodstream, and it is therefore used in cases of acute lymphoblastic leukemia (ALL) [...] Read more.

The enzyme L-asparaginase (L-asparagine amidohydrolase) catalyzes the breakdown of L-asparagine into aspartate and ammonia, which leads to an anti-neoplastic activity stemming from its capacity to deplete L-asparagine concentrations in the bloodstream, and it is therefore used in cases of acute lymphoblastic leukemia (ALL) to inhibit malignant cell growth. Nowadays, this anti-cancer enzyme, largely produced by Escherichia coli, is well established on the market. However, E. coli L-asparaginase therapy has side effects such as anaphylaxis, coagulation abnormality, low plasma half-life, hepatotoxicity, pancreatitis, protease action, hyperglycemia, and cerebral dysfunction. This review provides a perspective on the use of filamentous fungi as alternative cell factories for L-asparaginase production. Filamentous fungi, such as various Aspergillus species, have superior protein secretion capacity compared to yeast and bacteria and studies show their potential for the future production of proteins with humanized N-linked glycans. This article explores the past and present applications of this important enzyme and discusses the prospects for using filamentous fungi to produce safe eukaryotic asparaginases with high production yields. Full article

(This article belongs to the Special Issue Promising Industrial Enzymes)

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15 pages, 8825 KiB

Open AccessArticle

Highly Selective Nitrogen-Doped Graphene Quantum Dots/Eriochrome Cyanine Composite Photocatalyst for NADH Regeneration and Coupling of Benzylamine in Aerobic Condition under Solar Light

by Ruchi Singh, Rajesh K. Yadav, Ravindra K. Shukla, Satyam Singh, Atul P. Singh, Dilip K. Dwivedi, Ahmad Umar and Navneet K. Gupta

Catalysts 2023, 13(1), 199; https://doi.org/10.3390/catal13010199 - 14 Jan 2023

Cited by 4 | Viewed by 2296

Abstract

Photocatalysis is an ecofriendly and sustainable pathway for utilizing solar energy to convert organic molecules. In this context, using solar light responsive graphene-based materials for C–N bond activation and coenzyme regeneration (nicotinamide adenine dinucleotide hydrogen; NADH) is one of the utmost important and [...] Read more.

Photocatalysis is an ecofriendly and sustainable pathway for utilizing solar energy to convert organic molecules. In this context, using solar light responsive graphene-based materials for C–N bond activation and coenzyme regeneration (nicotinamide adenine dinucleotide hydrogen; NADH) is one of the utmost important and challenging tasks in this century. Herein, we report the synthesis of nitrogen-doped graphene quantum dots (NGQDs)-eriochrome cyanine (EC) solar light active highly efficient “NGQDs@EC” composite photocatalyst for the conversion of 4-chloro benzylamine into 4-chloro benzylamine, accompanied by the regeneration of NADH from NAD⁺, respectively. The NGQDs@EC composite photocatalyst system is utilized in a highly efficient and stereospecific solar light responsive manner, leading to the conversion of imine (98.5%) and NADH regeneration (55%) in comparison to NGQDs. The present research work highlights the improvements in the use of NGQDs@EC composite photocatalyst for stereospecific NADH regeneration and conversion of imine under solar light. Full article

(This article belongs to the Special Issue Catalytic Methods for the Synthesis of Carbon Nanodots and Their Applications)

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17 pages, 7340 KiB

Open AccessArticle

Alkaline Media Regulated NiFe-LDH-Based Nickel–Iron Phosphides toward Robust Overall Water Splitting

by Xiaohu Xu, Xinyue Yu, Kaiwei Guo, Lijuan Dong and Xiangyang Miao

Catalysts 2023, 13(1), 198; https://doi.org/10.3390/catal13010198 - 14 Jan 2023

Cited by 3 | Viewed by 2327

Abstract

The search for low-cost, high-performance, and robust stability bifunctional electrocatalysts to substitute noble metals-based counterparts for overall water splitting to generate clean and sustainable hydrogen energy is of great significance and challenges. Herein, a high-efficient bi-functional nickel–iron phosphide on NiFe alloy foam (denoted [...] Read more.

The search for low-cost, high-performance, and robust stability bifunctional electrocatalysts to substitute noble metals-based counterparts for overall water splitting to generate clean and sustainable hydrogen energy is of great significance and challenges. Herein, a high-efficient bi-functional nickel–iron phosphide on NiFe alloy foam (denoted as e-NFP/NFF) with 3D coral-like nanostructure was controllably constructed by means of alkali etching and the introduction of non-metallic atoms P. The unique superhydrophilic coral-like structure can not only effectively facilitate the exposure of catalytic active sites and increase the electroactive surface area, but also accelerate charge transport and bubble release. Furthermore, owing to the synergistic effect between the bicomponent of nickel–iron phosphides as well as the strong electronic interactions of the multiple metal sites, the as-fabricated catalyst behaves with excellent bifunctional performance for the hydrogen evolution reaction (overpotentials of 132 and 286 mV at 10 and 300 mA·cm⁻², respectively) and oxygen evolution reaction (overpotentials of 181 and 303 mV at 10 and 300 mA·cm⁻², respectively) in alkaline electrolytes. Impressively, cells with integrated e-NFP/NFF electrodes as a cathode and anode require only a low cell voltage (1.58 V) to drive a current density of 10 mA·cm⁻² for overall water splitting, along with remarkable stability in long-term electrochemical durability tests. This study provides a tunable synthetic strategy for the development of efficient and durable non-noble metal bifunctional catalysts based on the construction of an elaborate structure framework and rational design of the electronic structure. Full article

(This article belongs to the Special Issue Catalyzing Electrosynthesis)

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14 pages, 2878 KiB

Open AccessCommunication

Comparison of Catalytic Properties of the Easily Interconvertible, Water-Soluble [RuHCl(CO)(mtppms-Na)₃] and [RuH(H₂O)(CO)(mtppms-Na)₃][BF₄]

by Henrietta Horváth, Gábor Papp, Ferenc Joó and Ágnes Kathó

Catalysts 2023, 13(1), 197; https://doi.org/10.3390/catal13010197 - 13 Jan 2023

Viewed by 1120

Abstract

The effect of the mobile interconversion of [RuHCl(CO)(mtppms-Na)₃] 1, and [RuH(H₂O)(CO)(mtppms-Na)₃]⁺ 2, was studied in hydrogenation of phenylacetylene and cinnamaldehyde in aqueous–organic biphasic systems, as a function of the [...] Read more.

The effect of the mobile interconversion of [RuHCl(CO)(mtppms-Na)₃] 1, and [RuH(H₂O)(CO)(mtppms-Na)₃]⁺ 2, was studied in hydrogenation of phenylacetylene and cinnamaldehyde in aqueous–organic biphasic systems, as a function of the chloride concentration and the pH of the aqueous phase. Catalytic activity of the two complexes was also determined in homogeneous organic solvents without any additives. In the biphasic system, the rate of selective hydrogenation of phenylacetylene to styrene was strongly increased upon addition of NaCl, while the reaction of cinnamaldehyde slowed, with no change in product distribution. Both reactions responded with a rate decrease upon increasing the pH of the aqueous phase. It was concluded that hydrogenation of phenylacetylene was catalyzed by 1 with no chloride dissociation, while in the reduction of cinnamaldehyde, the aquo-complex 2 was the active catalytic species. Catalytic cycles were suggested to rationalize these findings. Full article

(This article belongs to the Special Issue Catalysis in Heterocyclic and Organometallic Synthesis II)

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23 pages, 3250 KiB

Open AccessFeature PaperReview

A Review of the Single-Step Flame Synthesis of Defective and Heterostructured TiO₂ Nanoparticles for Photocatalytic Applications

by Sovann Khan, Jin-Sung Park and Tatsumi Ishihara

Catalysts 2023, 13(1), 196; https://doi.org/10.3390/catal13010196 - 13 Jan 2023

Cited by 8 | Viewed by 2436

Abstract

Titanium dioxide (TiO₂) is an excellent UV-photocatalytic material that is widely used in various applications, including clean energy production, environmental remediation, and chemical production. However, the use of TiO₂ is limited in the field of visible light photocatalysis due to [...] Read more.

Titanium dioxide (TiO₂) is an excellent UV-photocatalytic material that is widely used in various applications, including clean energy production, environmental remediation, and chemical production. However, the use of TiO₂ is limited in the field of visible light photocatalysis due to its large bandgap and fast recombination rate between electron and hole pairs, which generally results in a low photocatalytic reaction. Defect/bandgap engineering by doping and the introduction of heterojunctions has been successfully employed to improve the photocatalytic activities of TiO₂ over a wide wavelength. To apply the unconventional structured TiO₂ with high photocatalytic performance to industries, the development of efficient methods for large-scale production is of high importance. Flame synthesis is a very promising method for the rapid production of nanoparticles. In this article, we summarize the latest reports on the synthesis of defective and heterostructured TiO₂ using the single-step method of flame synthesis. Fundamental understandings of reactor configurations, synthesis conditions, precursor preparation and their physicochemical properties are intensively discussed. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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18 pages, 4924 KiB

Open AccessArticle

Degradation of Textile Dye by Bimetallic Oxide Activated Peroxymonosulphate Process

by Hera Rashid and P. V. Nidheesh

Catalysts 2023, 13(1), 195; https://doi.org/10.3390/catal13010195 - 13 Jan 2023

Cited by 4 | Viewed by 1345

Abstract

The sulphate radical based advanced oxidation processes (AOPs) are highly in demand these days, owing to their numerous advantages. Herein, the Fe-Mn bimetallic oxide particle was used to activate peroxymonosulphate (PMS) for Rhodamine B (RhB) degradation. Three bimetallic catalysts were synthesized via the [...] Read more.

The sulphate radical based advanced oxidation processes (AOPs) are highly in demand these days, owing to their numerous advantages. Herein, the Fe-Mn bimetallic oxide particle was used to activate peroxymonosulphate (PMS) for Rhodamine B (RhB) degradation. Three bimetallic catalysts were synthesized via the chemical precipitation method with different concentrations of metals; Fe-Mn (1:1), Fe-Mn (1:2) and Fe-Mn (2:1). The best performance was shown by Fe-Mn (2:1) system at optimized conditions; 96% of RhB was removed at optimized conditions. Scavenging experiments displayed the clear dominance of hydroxyl radical in pH 3, while sulphate radical was present in a large amount at pH 7 and 10. The monometallic Fe and Mn oxides were also synthesized to confirm the synergistic effect that was present in the bimetallic oxide system. The application of optimized condition in real textile wastewater was conducted, which revealed the system works efficiently at high concentrations of PMS and catalyst dosage. Full article

(This article belongs to the Special Issue Trends in Catalytic Systems for Environmental Protection)

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12 pages, 3955 KiB

Open AccessFeature PaperArticle

Oxidative N-Dealkylation of N,N-Dimethylanilines by Non-Heme Manganese Catalysts

by Bashdar I. Meena, Dóra Lakk-Bogáth, Patrik Török and József Kaizer

Catalysts 2023, 13(1), 194; https://doi.org/10.3390/catal13010194 - 13 Jan 2023

Cited by 1 | Viewed by 1480

Abstract

Non-heme manganese(II) complexes [(IndH)Mn^IICl₂] (1) and [(N4Py*)Mn^II(CH₃CN)](ClO₄)₂ (2) with tridentate isoindoline and pentadentate polypyridyl ligands (IndH = 1,3-bis(2′-pyridylimino)isoindoline; N4Py* = N,N-bis(2-pyridylmethyl)-1,2- di(2-pyridyl)ethylamine) proved to be [...] Read more.

Non-heme manganese(II) complexes [(IndH)Mn^IICl₂] (1) and [(N4Py*)Mn^II(CH₃CN)](ClO₄)₂ (2) with tridentate isoindoline and pentadentate polypyridyl ligands (IndH = 1,3-bis(2′-pyridylimino)isoindoline; N4Py* = N,N-bis(2-pyridylmethyl)-1,2- di(2-pyridyl)ethylamine) proved to be suitable to catalyze the oxidative demethylation of N,N-dimethylaniline (DMA) with various oxidants such as tert-butyl hydroperoxide (TBHP), peracetic acid (PAA), and meta-chloroperoxybenzoic acid (mCPBA), resulting N-methylaniline (MA) as a main product with N-methylformanilide (MFA) as a result of a free-radical chain process under air. The effect of electron-donating and electron-withdrawing substituents on the aromatic ring on the relative reactivity of the substrates and on the product composition (MA/MFA) was also studied and showed a significant impact on the catalytic N-demethylation reaction. Based on the Hammett correlation with ρ = −0.38 (PAA), −0.45 (mCPBA), and −0.63 (TBHP) for 1 and ρ = −0.38 (PAA) and −0.37 (mCPBA) for 2, an electrophilic intermediate is suggested as the key oxidant. Furthermore, the spectral investigation (UV-Vis) resulted in direct evidence for the formation of a high-valent oxomanganese(IV) and a transient radical cation intermediate, p-Me-DMA^•+, suggesting that the initial step in the manganese-catalyzed oxidations is a fast electron-transfer between the amine and the high valent oxometal species. The mechanisms of the subsequent steps are discussed. Full article

(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)

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19 pages, 3777 KiB

Open AccessArticle

Integrated Photocatalytic Oxidation and Adsorption Approach for the Robust Treatment of Refinery Wastewater Using Hybrid TiO₂/AC

by Ihtisham Ul Haq, Waqas Ahmad, Imtiaz Ahmad, Amjad Shah, Muhammad Yaseen and Taj Muhammad

Catalysts 2023, 13(1), 193; https://doi.org/10.3390/catal13010193 - 13 Jan 2023

Cited by 2 | Viewed by 1870

Abstract

This study reports the removal of hydrocarbon (HC) pollutants from petroleum refinery wastewater by integrated photocatalytic oxidation and adsorption using a TiO₂/AC hybrid material. The hybrid adsorbent/catalyst was prepared by the impregnation of TiO₂ over AC and characterized by FTIR, [...] Read more.

This study reports the removal of hydrocarbon (HC) pollutants from petroleum refinery wastewater by integrated photocatalytic oxidation and adsorption using a TiO₂/AC hybrid material. The hybrid adsorbent/catalyst was prepared by the impregnation of TiO₂ over AC and characterized by FTIR, SEM, EDX, and XRD analyses. Under the optimized reaction conditions of pH 3, 30 °C, and 1000 mg TiO₂/AC per 500 mL of sample in 50 min, the integrated photocatalytic oxidation-adsorption achieved a net percentage removal of benzene, toluene, aniline, and naphthalene of 91% from model HC solutions. Under these conditions, for the treatment of real refinery wastewater, TiO₂/AC caused a 95% decrease in chemical oxygen demand (COD). The integrated photocatalytic oxidation and adsorption using TiO₂/AC showed a clear advantage over the individual adsorption and photocatalytic oxidation using AC and TiO₂, whereby about the same level of removal of model HCs and a decrease in the COD of refinery wastewater was attained in 105 min and 90 min, respectively, utilizing larger adsorbent/catalyst dosages. GC-MS analysis revealed that during the integrated process of adsorption-photocatalytic oxidation, all the parent HCs and oxidation byproducts were completely removed from the refinery wastewater. Based on the outstanding performance, cost-effectiveness, and environmental greenness, the newly designed TiO₂/AC via the integrated adsorption-photocatalytic oxidation can be counted as an effective alternative route for the large-scale processing of refinery wastewater. Full article

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

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24 pages, 7624 KiB

Open AccessFeature PaperReview

Recent Advances in g-C₃N₄-Based Photocatalysts for NO_x Removal

by Zhanyong Gu, Mengdie Jin, Xin Wang, Ruotong Zhi, Zhenghao Hou, Jing Yang, Hongfang Hao, Shaoyan Zhang, Xionglei Wang, Erpeng Zhou and Shu Yin

Catalysts 2023, 13(1), 192; https://doi.org/10.3390/catal13010192 - 13 Jan 2023

Cited by 3 | Viewed by 2381

Abstract

Nitrogen oxides (NO_x) pollutants can cause a series of environmental issues, such as acid rain, ground-level ozone pollution, photochemical smog and global warming. Photocatalysis is supposed to be a promising technology to solve NO_x pollution. Graphitic carbon nitride (g-C₃ [...] Read more.

Nitrogen oxides (NO_x) pollutants can cause a series of environmental issues, such as acid rain, ground-level ozone pollution, photochemical smog and global warming. Photocatalysis is supposed to be a promising technology to solve NO_x pollution. Graphitic carbon nitride (g-C₃N₄) as a metal-free photocatalyst has attracted much attention since 2009. However, the pristine g-C₃N₄ suffers from poor response to visible light, rapid charge carrier recombination, small specific surface areas and few active sites, which results in deficient solar light efficiency and unsatisfactory photocatalytic performance. In this review, we summarize and highlight the recent advances in g-C₃N₄-based photocatalysts for photocatalytic NO_x removal. Firstly, we attempt to elucidate the mechanism of the photocatalytic NO_x removal process and introduce the metal-free g-C₃N₄ photocatalyst. Then, different kinds of modification strategies to enhance the photocatalytic NO_x removal performance of g-C₃N₄-based photocatalysts are summarized and discussed in detail. Finally, we propose the significant challenges and future research topics on g-C₃N₄-based photocatalysts for photocatalytic NO_x removal, which should be further investigated and resolved in this interesting research field. Full article

(This article belongs to the Special Issue Advances in Heterojunction Photocatalysts)

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12 pages, 2371 KiB

Open AccessArticle

Composite of α-FeOOH and Mesoporous Carbon Derived from Indian Blackberry Seeds as Low-Cost and Recyclable Photocatalyst for Degradation of Ciprofloxacin

by Dimple P. Dutta and Sebin Abraham

Catalysts 2023, 13(1), 191; https://doi.org/10.3390/catal13010191 - 13 Jan 2023

Cited by 1 | Viewed by 1417

Abstract

This study aims to analyse the use of biowaste-derived carbon in enhancing the photocatalytic effect of Earth-abundant visible light active goethite (α−FeOOH). The biowaste material used in this case is seeds of the Indian blackberry fruit. The FeOOH/C composite has been synthesized using [...] Read more.

This study aims to analyse the use of biowaste-derived carbon in enhancing the photocatalytic effect of Earth-abundant visible light active goethite (α−FeOOH). The biowaste material used in this case is seeds of the Indian blackberry fruit. The FeOOH/C composite has been synthesized using an assisted sonochemical technique. The photocatalysts have been characterized using powder x-ray diffraction, nitrogen adsorption isotherms and scanning electron microscopy technique. FTIR and Raman studies have been carried out to understand the structure bonding correlation. The band gap has been ascertained using Tauc plots. The adsorption and consequent photodegradation of CIP have been studied via UV-visible spectroscopy and the mechanism has been ascertained by using radical quenching techniques. The charge separation efficiency has been ascertained through photoluminescence (PL) studies and electrochemical impedance studies (EIS). The pivotal role played by photogenerated holes (h⁺) in the photocatalytic degradation of CIP has been highlighted. The low cost biowaste-derived carbon as a constituent of the FeOOH/C composite shows great promise as a supporting material for enhancing the photocatalytic properties of such semiconductor materials. Full article

(This article belongs to the Section Environmental Catalysis)

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12 pages, 3218 KiB

Open AccessFeature PaperArticle

Ni-Pd-Incorporated Fe₃O₄ Yolk-Shelled Nanospheres as Efficient Magnetically Recyclable Catalysts for Reduction of N-Containing Unsaturated Compounds

by Dong Wang, Yi Li, Liangsong Wen, Jiangbo Xi, Pei Liu, Thomas Willum Hansen and Ping Li

Catalysts 2023, 13(1), 190; https://doi.org/10.3390/catal13010190 - 13 Jan 2023

Cited by 33 | Viewed by 2531

Abstract

The use of metal-based heterogeneous catalysts for the degradation of N-containing organic dyes has attracted much attention due to their excellent treatment efficiency and capability. Here, we report the synthesis of heterometals (Ni and Pd)-incorporated Fe₃O₄ (Ni-Pd/Fe₃O₄ [...] Read more.

The use of metal-based heterogeneous catalysts for the degradation of N-containing organic dyes has attracted much attention due to their excellent treatment efficiency and capability. Here, we report the synthesis of heterometals (Ni and Pd)-incorporated Fe₃O₄ (Ni-Pd/Fe₃O₄) yolk-shelled nanospheres for the catalytic reduction of N-containing organic dyes using a facile combination of solvothermal treatment and high-temperature annealing steps. Benefiting from the magnetic properties and the yolk-shelled structure of the Fe₃O₄ support, as well as the uniformly dispersed active heterometals incorporated in the shell and yolk of spherical Fe₃O₄ nanoparticles, the as-prepared Ni-Pd/Fe₃O₄ composite shows excellent recyclability and enhanced catalytic activity for three N-containing organic dyes (e.g., 4-nitrophenol, Congo red, and methyl orange) compared with its mono metal counterparts (e.g., Ni/Fe₃O₄ and Pd/Fe₃O₄). In the 4-nitrophenol reduction reaction, the catalytic activity of Ni-Pd/Fe₃O₄ was superior to many Fe₃O₄-supported nanocatalysts reported within the last five years. This work provides an effective strategy to boost the activity of iron oxide-based catalytic materials via dual or even multiple heterometallic incorporation strategy and sheds new light on environmental catalysis. Full article

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

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23 pages, 3482 KiB

Open AccessReview

Applications of Spent Lithium Battery Electrode Materials in Catalytic Decontamination: A Review

by Pu Wang, Yaoguang Guo, Jie Guan and Zhaohui Wang

Catalysts 2023, 13(1), 189; https://doi.org/10.3390/catal13010189 - 13 Jan 2023

Cited by 1 | Viewed by 1906

Abstract

For a large amount of spent lithium battery electrode materials (SLBEMs), direct recycling by traditional hydrometallurgy or pyrometallurgy technologies suffers from high cost and low efficiency and even serious secondary pollution. Therefore, aiming to maximize the benefits of both environmental protection and e-waste [...] Read more.

For a large amount of spent lithium battery electrode materials (SLBEMs), direct recycling by traditional hydrometallurgy or pyrometallurgy technologies suffers from high cost and low efficiency and even serious secondary pollution. Therefore, aiming to maximize the benefits of both environmental protection and e-waste resource recovery, the applications of SLBEM containing redox-active transition metals (e.g., Ni, Co, Mn, and Fe) for catalytic decontamination before disposal and recycling has attracted extensive attention. More importantly, the positive effects of innate structural advantages (defects, oxygen vacancies, and metal vacancies) in SLBEMs on catalytic decontamination have gradually been unveiled. This review summarizes the pretreatment and utilization methods to achieve excellent catalytic performance of SLBEMs, the key factors (pH, reaction temperature, coexisting anions, and catalyst dosage) affecting the catalytic activity of SLBEM, the potential application and the outstanding characteristics (detection, reinforcement approaches, and effects of innate structural advantages) of SLBEMs in pollution treatment, and possible reaction mechanisms. In addition, this review proposes the possible problems of SLBEMs in practical decontamination and the future outlook, which can help to provide a broader reference for researchers to better promote the implementation of “treating waste to waste” strategy. Full article

(This article belongs to the Special Issue Advanced Catalysts for Persulfate Activation)

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18 pages, 1657 KiB

Open AccessFeature PaperArticle

Full-Scale O₃/Micro-Nano Bubbles System Based Advanced Oxidation as Alternative Tertiary Treatment in WWTP Effluents

by Laura Ponce-Robles, Aránzazu Pagán-Muñoz, Andrés Jesús Lara-Guillén, Beatriz Masdemont-Hernández, Teresa Munuera-Pérez, Pedro Antonio Nortes-Tortosa and Juan José Alarcón-Cabañero

Catalysts 2023, 13(1), 188; https://doi.org/10.3390/catal13010188 - 13 Jan 2023

Cited by 2 | Viewed by 2294

Abstract

Wastewater treatment plant effluents can be an important source of contamination in agricultural reuse practices, as pharmaceuticals are poorly degraded by conventional treatments and can enter crops, thereby becoming a toxicological risk. Therefore, advanced tertiary treatments are required. Ozone (O₃) is [...] Read more.

Wastewater treatment plant effluents can be an important source of contamination in agricultural reuse practices, as pharmaceuticals are poorly degraded by conventional treatments and can enter crops, thereby becoming a toxicological risk. Therefore, advanced tertiary treatments are required. Ozone (O₃) is a promising alternative due to its capacity to degrade pharmaceutical compounds, together with its disinfecting power. However, mass transfer from the gas to the liquid phase can be a limiting step. A novel alternative for increased ozone efficiency is the combination of micro-nano bubbles (MNBs). However, this is still a fairly unknown method, and there are also many uncertainties regarding their implementation in large-scale systems. In this work, a combined O₃/MNBs full-scale system was installed in a WWTP to evaluate the removal efficiency of 12 pharmaceuticals, including COVID-19-related compounds. The results clearly showed that the use of MNBs had a significantly positive contribution to the effects of ozone, reducing energy costs with respect to conventional O₃ processes. Workflow and ozone production were key factors for optimizing the system, with the highest efficiencies achieved at 2000 L/h and 15.9 gO₃/h, resulting in high agronomic water quality effluents. A first estimation of the transformation products generated was described, jointly with the energy costs required. Full article

(This article belongs to the Special Issue Trends in Environmental Applications of Advanced Oxidation Processes)

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12 pages, 2046 KiB

Open AccessFeature PaperArticle

Computational Study on the Catalytic Performance of Single-Atom Catalysts Anchored on g-CN for Electrochemical Oxidation of Formic Acid

by Abdul Qadeer, Meiqi Yang, Yuejie Liu, Qinghai Cai and Jingxiang Zhao

Catalysts 2023, 13(1), 187; https://doi.org/10.3390/catal13010187 - 13 Jan 2023

Cited by 1 | Viewed by 1774

Abstract

The electrochemical formic acid oxidation reaction (FAOR) has attracted great attention due to its high volumetric energy density and high theoretical efficiency for future portable electronic applications, for which the development of highly efficient and low-cost electrocatalysts is of great significance. In this [...] Read more.

The electrochemical formic acid oxidation reaction (FAOR) has attracted great attention due to its high volumetric energy density and high theoretical efficiency for future portable electronic applications, for which the development of highly efficient and low-cost electrocatalysts is of great significance. In this work, taking single-atom catalysts (SACs) supported on graphitic carbon nitrides (g-CN) as potential catalysts, their catalytic performance for the FAOR was systemically explored by means of density functional theory computations. Our results revealed that the strong hybridization with the unpaired lone electrons of N atoms in the g-CN substrate ensured the high stability of these anchored SACs and endowed them with excellent electrical conductivity. Based on the computed free energy changes of all possible elementary steps, we predicted that a highly efficient FAOR could be achieved on Ru/g-CN with a low limiting potential of −0.15 V along a direct pathway of HCOOH_(aq) → HCOOH* → HCOO* → CO₂* → CO_2(g), in which the formation of HCOO* was identified as the potential-determining step, while the rate-determining step was located at the CO₂* formation, with a moderate kinetic barrier of 0.89 eV. Remarkably, the moderate d-band center and polarized charge of the Ru active site caused the Ru/g-CN catalyst to exhibit an optimal binding strength with various reaction intermediates, explaining well its superior FAOR catalytic performance. Hence, the single Ru atom anchored on g-CN could be utilized as a promising SAC for the FAOR, which opens a new avenue to further develop novel catalysts for a sustainable FAOR in formic-acid-based fuel cells. Full article

(This article belongs to the Special Issue Theory-Guided Electrocatalysis and Photocatalysis)

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19 pages, 3202 KiB

Open AccessArticle

Effect of Calcination Temperature of SiO₂/TiO₂ Photocatalysts on UV-VIS and VIS Removal Efficiency of Color Contaminants

by Aleksandra Babyszko, Agnieszka Wanag, Ewelina Kusiak-Nejman and Antoni Waldemar Morawski

Catalysts 2023, 13(1), 186; https://doi.org/10.3390/catal13010186 - 13 Jan 2023

Cited by 4 | Viewed by 1766

Abstract

This paper presents the effect of fumed silica modification and calcination temperature on the physicochemical properties of photocatalysts and their activity under the UV-VIS and VIS light range. The materials were obtained by hydrolysis of titanium tetraisopropoxide (TTIP) combined with a calcination step. [...] Read more.

This paper presents the effect of fumed silica modification and calcination temperature on the physicochemical properties of photocatalysts and their activity under the UV-VIS and VIS light range. The materials were obtained by hydrolysis of titanium tetraisopropoxide (TTIP) combined with a calcination step. The obtained nanomaterials were characterized using analytical methods such as X-ray diffraction XRD, FT-IR/DRS infrared spectroscopy, UV-Vis/DRS spectroscopy and SEM scanning electron microscopy. BET specific surface area and zeta potential were also measured. It was observed that SiO₂ modification inhibited the transformation phase of anatase to rutile and the increase in crystallite size during calcination. The calcination process contributed to a change in the surface character of photocatalysts under study from positively to negatively charged. The photocatalytic activity of samples was identified by determining the methylene blue decomposition under UV-VIS and VIS light. Experimental results showed that the addition of SiO₂ and the calcination process increased the photoactivity. The obtained materials showed higher activity compared to the reference samples. It was found that the degree of dye removal increased along with increased calcination temperature. The highest activity was observed for photocatalyst SiO₂(11.1%)/TiO₂_600. Full article

(This article belongs to the Special Issue Nanostructured Materials for Solar and Visible Light Driven Photocatalysis)

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15 pages, 5297 KiB

Open AccessArticle

Novel Complex Titanium NASICON-Type Phosphates as Acidic Catalysts for Ethanol Dehydration

by Anna I. Zhukova, Elena A. Asabina, Andrey N. Kharlanov, Diana A. Osaulenko, Sofia G. Chuklina, Dmitry Yu. Zhukov, Vladimir I. Pet’kov and Dina V. Deyneko

Catalysts 2023, 13(1), 185; https://doi.org/10.3390/catal13010185 - 13 Jan 2023

Cited by 1 | Viewed by 1756

Abstract

The conversion of ethanol towards ethylene and diethyl ether in the presence of catalysts requires special consideration from the perspective of green chemistry. Ethanol dehydration was studied on a complex titanium phosphate MAlTiP (M_0.5(1+x)Al_xTi_2-x(PO₄)₃ [...] Read more.

The conversion of ethanol towards ethylene and diethyl ether in the presence of catalysts requires special consideration from the perspective of green chemistry. Ethanol dehydration was studied on a complex titanium phosphate MAlTiP (M_0.5(1+x)Al_xTi_2-x(PO₄)₃ with M = Ni, Mn (x = 0; 0.2)) catalysts, alongside a NASICON-type structure synthesized by the sol–gel method. The initial catalysts were characterized by N₂ gas sorption, SEM, XRD and spectroscopic methods (Raman and DRIFT of adsorbed CO and C₆H₆). The results revealed that all catalysts exhibited high activity and selectivity at 300–420 °C. The conversion of ethanol increases with the reaction temperature, reaching 67–80% at 420 °C. The MnAlTiP exhibited the highest ethylene selectivity among other catalysts, with 87% at 420 °C. The aluminum modification improved the acid properties of the catalysts, due to the appearance of Lewis acid sites (LAS) and the strength moderate Brønsted acid sites (BAS). It was shown that the activity of complex phosphates in ethanol dehydration increases with the strength of the Brønsted acid sites (BAS). Full article

(This article belongs to the Special Issue Catalysts in Energy Applications II)

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12 pages, 2400 KiB

Open AccessArticle

Removal Efficiency and Performance Optimization of Organic Pollutants in Wastewater Using New Biochar Composites

by Guodong Wang, Shirong Zong, Hang Ma, Banglong Wan and Qiang Tian

Catalysts 2023, 13(1), 184; https://doi.org/10.3390/catal13010184 - 13 Jan 2023

Cited by 3 | Viewed by 1347

Abstract

The purpose is to optimize the catalytic performance of biochar (BC), improve the removal effect of BC composites on organic pollutants in wastewater, and promote the recycling and sustainable utilization of water resources. Firstly, the various characteristics and preparation principles of new BC [...] Read more.

The purpose is to optimize the catalytic performance of biochar (BC), improve the removal effect of BC composites on organic pollutants in wastewater, and promote the recycling and sustainable utilization of water resources. Firstly, the various characteristics and preparation principles of new BC are discussed. Secondly, the types of organic pollutants in wastewater and their removal principles are discussed. Finally, based on the principle of removing organic pollutants, BC/zero valent iron (BC/ZVI) composite is designed, among which BC is mainly used for catalysis. The effect of BC/ZVI in removing tetracycline (TC) is comprehensively evaluated. The research results reveal that the TC removal effect of pure BC is not ideal, and that of ZVI is general. The BC/ZVI composite prepared by combining the two has a better removal effect on TC, with a removal amount of about 275 mg/g. Different TC concentrations, ethylene diamine tetraacetic acid (EDTA), pH environment, tert-butanol, and calcium ions will affect the TC removal effect of BC composites. The overall effect is the improvement of the TC removal amount of BC composites. It reveals that BC has a very suitable catalytic effect on ZVI, and the performance of BC composite material integrating BC catalyst and ZVI has been effectively improved, which can play a very suitable role in wastewater treatment. This exploration provides a technical reference for the effective removal of organic pollutants in wastewater and contributes to the development of water resource recycling. Full article

(This article belongs to the Special Issue New Insights into Novel Catalysts for Treatment of Pollutants in Wastewater)

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11 pages, 2547 KiB

Open AccessArticle

Identification of New Amylolytic Enzymes from Marine Symbiotic Bacteria of Bacillus Species

by Mohammad Reza Erfanimoghadam and Ahmad Homaei

Catalysts 2023, 13(1), 183; https://doi.org/10.3390/catal13010183 - 13 Jan 2023

Cited by 3 | Viewed by 2076

Abstract

α-amylases are one of the most common and important industrial enzymes widely used in various industries. The present study was conducted with the aim of isolating and identifying symbiotic α-amylase enzyme-producing bacteria in the intestine of Silago Sihama and Rasterliger Canagorta fish living [...] Read more.

α-amylases are one of the most common and important industrial enzymes widely used in various industries. The present study was conducted with the aim of isolating and identifying symbiotic α-amylase enzyme-producing bacteria in the intestine of Silago Sihama and Rasterliger Canagorta fish living in Qeshm Island, Hormozgan. The intestinal symbiotic bacteria of these species were isolated using nutrient agar culture medium; then, α-amylase producing bacteria were screened using a special culture medium containing starch and the Lugol’s solution test. The α-amylase enzyme activity of enzyme-producing bacteria was measured using the starch substrate. Finally, bacteria with the highest enzyme activity were selected and identified by the 16S rRNA gene sequence analysis. The results showed that out of 22 isolated bacteria, 10 were able to grow in a special culture medium, and 5 strains of these 10 bacteria had the ability to produce relatively stronger halos. The four bacterial strains belonging to the genus Bacillus that had the highest α-amylase enzyme activity were identified and registered in the NCBI gene database as B. subtilis strains HR13, HR14, HR15, and HR16. Among these four strains, two strains of B. subtilis, HR13 and HR16, displayed high enzyme activity and maximum activity at 60 °C at pH values of 5 and 7, respectively. α-Amylase enzymes isolated from marine symbiotic bacteria of Bacillus species can be considered potential candidates for application in various industries. Full article

(This article belongs to the Special Issue Microbial Biocatalysis)

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13 pages, 2922 KiB

Open AccessArticle

Performance of Fuel Electrode-Supported Tubular Protonic Ceramic Cells Prepared through Slip Casting and Dip-Coating Methods

by Youcheng Xiao, Mengjiao Wang, Di Bao, Zhen Wang, Fangjun Jin, Yaowen Wang and Tianmin He

Catalysts 2023, 13(1), 182; https://doi.org/10.3390/catal13010182 - 12 Jan 2023

Cited by 2 | Viewed by 1816

Abstract

Fuel electrode-supported tubular protonic ceramic cells (FETPCCs) based on the BaZr_0.4Ce_0.4Y_0.15Zn_0.05O_3−δ (BZCYZ) membrane electrolyte was fabricated through a two-step method, in which the polyporous electrode-support tube was prepared with a traditional slip casting technique [...] Read more.

Fuel electrode-supported tubular protonic ceramic cells (FETPCCs) based on the BaZr_0.4Ce_0.4Y_0.15Zn_0.05O_3−δ (BZCYZ) membrane electrolyte was fabricated through a two-step method, in which the polyporous electrode-support tube was prepared with a traditional slip casting technique in a plaster mold, and the BZCYZ membrane was produced by a dip-coating process on the outside surface of the electrode-support tube. The dense thin-film electrolyte of BZCYZ with a thickness of ~25 μm was achieved by cofiring the fuel electrode support and electrolyte membrane at 1450 °C for 6 h. The electrochemical performances of the FETPCCs were tested under different solid oxide cell modes. In protonic ceramic fuel cell (PCFC) mode, the peak power densities of the cell reached 151–191 mW·cm⁻² at 550–700 °C and exhibited relatively stable performance during continuous operation over 100 h at 650 °C. It was found that the major influence on the performance of tubular PCFC was the resistance and cathode current collectors. Additionally, in protonic ceramic electrolysis cell (PCEC) mode, the current densities of 418–654 mA·cm⁻² were obtained at 600–700 °C with the applied voltage of 2.0 V when exposed to 20% CO₂–80% H₂ and 3% H₂O/air. Using distribution of relaxation time analysis, the electrolytic rate-limiting step of the PCEC model was determined as the adsorption and dissociation of the gas on the electrode surface. Full article

(This article belongs to the Special Issue Advanced Catalysts for Electrochemical Energy Storage and Conversion)

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