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Transition Metal Catalysis

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A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Environmental Catalysis".

Deadline for manuscript submissions: closed (20 November 2021) | Viewed by 39072

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Prof. Dr. Alessandro Di Michele

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Department of Physics and Geology, University of Perugia, Perugia, Italy
Interests: nanomaterials; sonochemistry; catalysis; electron microscopy imaging
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Dr. Carlo Pirola

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Dipartimento di Chimica, Università degli Studi di Milano, 20133 Milano, Italy
Interests: heterogeneous catalysis; process simulation; environmental chemistry; separations; scale-up; photocatalysis
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Special Issue Information

Dear Colleagues,

Transition metal catalysis has attracted a great deal of interest due to its efficiency, greenness, and convenient use. Moreover, it plays an important role in both academia and industry, where selectivity, activity, and stability are crucial parameters to control.

In particular, transition metals represent excellent catalysts in heterogeneous and homogeneous catalytic research. In fact, they have been proven to lower the activation barrier for chemical reactions thanks to their ability to lend electrons or withdraw electrons from the reagent, depending on the nature of the reaction. Their capacity to be in a variety of oxidation states, to interchange between the oxidation states, and to form complexes with the reagents allows them to be used in a huge variety of catalytic processes, from polymerization processes to bio-syngas transformation, fuel cell applications, and modern organic synthesis.

This Special Issue will focus on the use of transition metal catalysis in green and sustainable chemical processes. Particular importance will be placed on its application in CO₂ transformation, energy harvesting, green synthesis, and environmental remediation processes.

We cordially invite you to submit a manuscript for consideration and possible publication. We hope this topic is of interest and look forward to hearing from you.

Prof. Dr. Alessandro Di Michele
Prof. Dr. Carlo Pirola
Guest Editors

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

heterogeneous catalysis;
homogeneous catalysis;
green synthesis;
CO₂;
energy harvesting;
environmental remediation.

Published Papers (12 papers)

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Research

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10 pages, 4000 KiB

Open AccessArticle

A Nickel Coated Copper Substrate as a Hydrogen Evolution Catalyst

by Poshan Kumar Reddy Kuppam, K. M. M. D. K. Kimbulapitiya, Srikanth Vuppala, Kuangye Wang, G. Phaneendra Reddy, Krishna P. Pande, Po-Tsung Lee and Yun-Lun Chueh

Catalysts 2022, 12(1), 58; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12010058 - 05 Jan 2022

Cited by 4 | Viewed by 2441

Abstract

Replacing precious metals with low-cost metals is the best solution for large scale production. Copper is known for its excellent conductivity and thermal management applications. When it comes to hydrogen evolution reaction, it is highly unstable, especially in KOH solution. In this paper, we approached a simple method to reduce corrosion and improve the performance by depositing nickel-molybdenum oxide and nickel on copper substrates and the achieved tafel slopes of 115 mV/dec and 117 mV/dec at 10 mA/cm². While at first, molybdenum oxide coated samples showed better performance after 100 cycles of stability tests, the onset potential rapidly changed. Cu-Ni, which was deposited using the electron gun evaporation (e-gun), has shown better performance with 0.28 V at 10 mA/cm² and led to stability after 100 cycles. Our results show that when copper is alloyed with nickel, it acts as a promising hydrogen evolution reaction (HER) catalyst. Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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15 pages, 4652 KiB

Open AccessArticle

Co Loading Adjustment for the Effective Obtention of a Sedative Drug Precursor through Efficient Continuous-Flow Chemoselective Hydrogenation of 2-Methyl-2-Pentenal

by Antonio Jesús Fernández-Ropero, Bartosz Zawadzki, Krzysztof Matus, Wojciech Patkowski, Mirosław Krawczyk, Dmytro Lisovytskiy, Wioletta Raróg-Pilecka and Anna Śrębowata

Catalysts 2022, 12(1), 19; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12010019 - 25 Dec 2021

Cited by 1 | Viewed by 2806

Abstract

This work presents the effect of Co loading on the performance of CNR115 carbon-supported catalysts in the continuous-flow chemoselective hydrogenation of 2-methyl-2-pentenal for the obtention of 2-methylpentanal, an intermediate in the synthesis of the sedative drug meprobamate. The Co loading catalysts (2, 6, 10, and 14 wt.%) were characterized by Brunauer–Emmett–Teller (BET) surface area analysis, transmission electron microscopy (TEM), H₂ temperature-programmed reduction (H₂-TPR), temperature-programmed desorption of hydrogen (H₂-TPD) analysis, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy for selected samples, and have been studied as hydrogenation catalysts at different pressure and temperature ranges. The results reveal that a certain amount of Co is necessary to achieve significant conversion values. However, excessive loading affects the morphological parameters, such as the surface area available for hydrogen adsorption and the particle size, preventing an increase in conversion, despite the increased presence of Co. Moreover, the larger particle size, caused by increasing the loading, alters the chemoselectivity, favouring the formation of 2-methyl-2-pentenol and, thus, decreasing the selectivity towards the desired product. The 6 wt.% Co-loaded material demonstrates the best catalytic performance, which is related to the formation of NPs with optimum size. Almost 100% selectivity towards 2-methylpentanal was obtained for the catalysts with lower Co loading (2 and 6 wt.%). Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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11 pages, 3779 KiB

Open AccessArticle

Atmospheric Pressure Catalytic Vapor Deposition of Graphene on Liquid In and Cu-In Alloy Substrates

by Maryam A. Saeed, Ian A. Kinloch and Brian Derby

Catalysts 2021, 11(11), 1318; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11111318 - 30 Oct 2021

Cited by 1 | Viewed by 1542

Abstract

Liquid substrates are great candidates for the growth of high-quality graphene using chemical vapour deposition (CVD) due to their atomically flat and defect free surfaces. A detailed study of graphene growth using atmospheric pressure CVD (APCVD) on liquid indium (In) was conducted. It was found that the effect of the growth parameters on the quality of the graphene produced is highly dependent on the properties of the substrate used. A short residence time of 6.8 sec for the reactive gases led to a high graphene quality, indicating the good catalytic behaviour of In. The role of hydrogen partial pressure was found to be crucial, with monolayer and bilayer graphene films with a low defect density obtained at low P_H2 (38.6 mbar), whilst more defective, thicker graphene films with a partial coverage being obtained at high P_H2 (74.3 mbar). The graphene deposition was insensitive to growth time as the graphene growth on liquid In was found to self-limit to bilayer. For further investigation, five compositions of Cu-In alloys were made by arc-melting. Graphene was then grown using the optimum conditions for In and the quality of the graphene was found to degrade with increasing Cu wt.%. This work will aid the future optimisation of the growth conditions based upon the substrate’s properties. Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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11 pages, 2878 KiB

Open AccessFeature PaperArticle

Pd–Au Bimetallic Catalysts for the Hydrogenation of Muconic Acid to Bio-Adipic Acid

by Sofia Capelli, Ilaria Barlocco, Federico Maria Scesa, Xiaohui Huang, Di Wang, Francesca Tessore, Alberto Villa, Alessandro Di Michele and Carlo Pirola

Catalysts 2021, 11(11), 1313; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11111313 - 29 Oct 2021

Cited by 5 | Viewed by 2229

Abstract

The hydrogenation reaction of muconic acid, produced from biomass using fermentative processes, to bio-adipic acid is one of the most appealing green emerging chemical process. This reaction can be promoted by catalysts based on a metal belonging to the platinum group, and the use of a second metal can preserve and increase their activity. Pd–Au bimetallic nanoparticle samples supported on high-temperature, heat-treated carbon nanofibers were prepared using the sol immobilization method, changing the Pd–Au molar ratio. These catalysts were characterized by TEM, STEM, and XPS analysis and tested in a batch reactor pressurized with hydrogen, where muconic acid dissolved in water was converted to adipic acid. The synthesized Pd–Au bimetallic catalysts showed higher activity than monometallic Au and Pd material and better stability during the recycling tests. Moreover, the selectivity toward the mono-unsaturated changed by decreasing the Pd/Au molar ratio: the higher the amount of gold, the higher the selectivity toward the intermediates. Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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18 pages, 4027 KiB

Open AccessArticle

Mayenite-Based Electride C12A7e⁻: A Reactivity and Stability Study

by Sebastian Weber, Sebastian Schäfer, Mattia Saccoccio, Nils Ortner, Marko Bertmer, Karsten Seidel, Stefan Berendts, Martin Lerch, Roger Gläser, Holger Kohlmann and Stephan A. Schunk

Catalysts 2021, 11(3), 334; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11030334 - 05 Mar 2021

Cited by 5 | Viewed by 3288

Abstract

Ru supported on mayenite electride, [Ca₂₄Al₂₈O₆₄]⁴⁺(e⁻)₄ a calcium aluminum oxide denoted as C12A7e⁻, are described in the literature as highly active catalysts for ammonia synthesis, especially under conditions of low absolute pressure. In this study, we investigated the application of recently reported plasma arc melting synthesized C12A7e⁻ (aluminum solid reductant) as supports of Ru/C12A7e⁻ catalysts in ammonia synthesis up to pressures of 7.6 MPa. Together with the plasma-arc-melting-based catalyst support, we investigated a similar plasma-synthesized C12A7e⁻ (graphite solid reductant) and a vacuum-sintering-based C12A7e⁻. Complementary to the catalytic tests, we applied ²H solid-state NMR spectroscopy, DRUVVis-spectroscopy, thermal analysis and PXRD to study and characterize the reactivity of different plasma-synthesized and vacuum-sintered C12A7e⁻ towards H₂/D₂ and H₂O. The catalysts showed an immediate deactivation at pressures > 1 MPa, which can be explained by irreversible hydride formation at higher pressures, as revealed by reactivity tests of C12A7e⁻ towards H₂/D₂. The direct formation of C12A7:D from C12A7e⁻ is proven. It can be concluded that the application of Ru/C12A7e⁻ catalysts at the industrial scale has limited prospects due to irreversible hydride formation at relevant pressures > 1 MPa. Furthermore, we report an in-depth study relating to structural changes in the material in the presence of H₂O. Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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9 pages, 1434 KiB

Open AccessArticle

Fe₃ Cluster Anchored on the C₂N Monolayer for Efficient Electrochemical Nitrogen Fixation

by Bing Han, Haihong Meng, Fengyu Li and Jingxiang Zhao

Catalysts 2020, 10(9), 974; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10090974 - 29 Aug 2020

Cited by 15 | Viewed by 3878

Abstract

Under the current double challenge of energy and the environment, an effective nitrogen reduction reaction (NRR) has become a very urgent need. However, the largest production of ammonia gas today is carried out by the Haber–Bosch process, which has many disadvantages, among which energy consumption and air pollution are typical. As the best alternative procedure, electrochemistry has received extensive attention. In this paper, a catalyst loaded with Fe₃ clusters on the two-dimensional material C₂N (Fe₃@C₂N) is proposed to achieve effective electrochemical NRR, and our first-principles calculations reveal that the stable Fe₃@C₂N exhibits excellent catalytic performance for electrochemical nitrogen fixation with a limiting potential of 0.57 eV, while also suppressing the major competing hydrogen evolution reaction. Our findings will open a new door for the development of non-precious single-cluster catalysts for effective nitrogen reduction reactions. Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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9 pages, 2000 KiB

Open AccessArticle

Methane Conversion over C₂N-Supported Fe₂ Dimers

by Haihong Meng, Bing Han, Fengyu Li and Jingxiang Zhao

Catalysts 2020, 10(9), 973; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10090973 - 29 Aug 2020

Cited by 2 | Viewed by 2652

Abstract

Methane is a vast hydrocarbon resource around the globe that has the potential to replace petroleum as a raw material and energy source. Therefore, the catalytic conversion of methane into high value-added chemicals is significantly important for the utilization of this hydrocarbon resource. However, this is a great challenge due to the high-energy input required to overcome the reaction barrier. Herein, a highly active catalytic conversion process of methane on an iron dimer anchored on a two-dimensional (2D) C₂N monolayer (Fe₂@C₂N) is reported. Density functional theory calculations reveal that the superior properties of Fe₂@C₂N can be attributed to the formation of the Fe-O-Fe intermediate with H₂O₂ as the O-donor molecule, which facilitates the formation of methyl radicals and promotes the conversion of methane. This finding could pave the way toward highly efficient non-precious metal catalysts for methane oxidation reactions. Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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Review

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44 pages, 11933 KiB

Open AccessFeature PaperReview

Recent Progress on Transition Metal Based Layered Double Hydroxides Tailored for Oxygen Electrode Reactions

by Jing Wang, Heng Kong, Haihong Zhong, Yu Jiang, Fei Guo, Nicolas Alonso-Vante and Yongjun Feng

Catalysts 2021, 11(11), 1394; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11111394 - 18 Nov 2021

Cited by 9 | Viewed by 3847

Abstract

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), namely, so-called oxygen electrode reactions, are two fundamental half-cell reactions in the energy storage and conversion devices, e.g., zinc–air batteries and fuel cells. However, the oxygen electrode reactions suffer from sluggish kinetics, large overpotential and complicated reaction paths, and thus require efficient and stable electrocatalysts. Transition-metal-based layered double hydroxides (LDHs) and their derivatives have displayed excellent catalytic performance, suggesting a major contribution to accelerate electrochemical reactions. The rational regulation of electronic structure, defects, and coordination environment of active sites via various functionalized strategies, including tuning the chemical composition, structural architecture, and topotactic transformation process of LDHs precursors, has a great influence on the resulting electrocatalytic behavior. In addition, an in-depth understanding of the structural performance and chemical-composition-performance relationships of LDHs-based electrocatalysts can promote further rational design and optimization of high-performance electrocatalysts. Finally, prospects for the design of efficient and stable LDHs-based materials, for mass-production and large-scale application in practice, are discussed. Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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80 pages, 34956 KiB

Open AccessReview

Synthesis of Indoles via Intermolecular and Intramolecular Cyclization by Using Palladium-Based Catalysts

by Ayesha, Muhammad Bilal, Nasir Rasool, Samreen Gul Khan, Umer Rashid, Humaira Altaf and Imtiaz Ali

Catalysts 2021, 11(9), 1018; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11091018 - 24 Aug 2021

Cited by 15 | Viewed by 5365

Abstract

As part of natural products or biologically active compounds, the synthesis of nitrogen-containing heterocycles is becoming incredibly valuable. Palladium is a transition metal that is widely utilized as a catalyst to facilitate carbon-carbon and carbon-heteroatom coupling; it is used in the synthesis of various heterocycles. This review includes the twelve years of successful indole synthesis using various palladium catalysts to establish carbon-carbon or carbon-nitrogen coupling, as well as the conditions that have been optimized. Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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23 pages, 9357 KiB

Open AccessReview

Recent Advances in Non-Precious Transition Metal/Nitrogen-doped Carbon for Oxygen Reduction Electrocatalysts in PEMFCs

by Meixiu Song, Yanhui Song, Wenbo Sha, Bingshe Xu, Junjie Guo and Yucheng Wu

Catalysts 2020, 10(1), 141; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10010141 - 20 Jan 2020

Cited by 44 | Viewed by 6125

Abstract

The proton exchange membrane fuel cells (PEMFCs) have been considered as promising future energy conversion devices, and have attracted immense scientific attention due to their high efficiency and environmental friendliness. Nevertheless, the practical application of PEMFCs has been seriously restricted by high cost, low earth abundance and the poor poisoning tolerance of the precious Pt-based oxygen reduction reaction (ORR) catalysts. Noble-metal-free transition metal/nitrogen-doped carbon (M–N_xC) catalysts have been proven as one of the most promising substitutes for precious metal catalysts, due to their low costs and high catalytic performance. In this review, we summarize the development of M–N_xC catalysts, including the previous non-pyrolyzed and pyrolyzed transition metal macrocyclic compounds, and recent developed M–N_xC catalysts, among which the Fe–N_xC and Co–N_xC catalysts have gained our special attention. The possible catalytic active sites of M–N_xC catalysts towards the ORR are also analyzed here. This review aims to provide some guidelines towards the design and structural regulation of non-precious M–N_xC catalysts via identifying real active sites, and thus, enhancing their ORR electrocatalytic performance. Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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Other

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2 pages, 178 KiB

Open AccessReply

Reply to Inoue et al. Comment on “Weber et al. Mayenite-Based Electride C12A7e⁻: A Reactivity and Stability Study. Catalysts 2021, 11, 334”

by Sebastian Weber and Stephan A. Schunk

Catalysts 2021, 11(10), 1155; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11101155 - 26 Sep 2021

Cited by 1 | Viewed by 1317

Abstract

With gratitude, we would like to thank Yasunori Inoue, Masaaki Kitano and Hideo Hosono for their comments on our recently published article and express our appreciation for the critical discussion of our results [...] Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

2 pages, 397 KiB

Open AccessComment

Comment on Weber et al. Mayenite-Based Electride C12A7e⁻: A Reactivity and Stability Study. Catalysts 2021, 11, 334

by Yasunori Inoue, Masaaki Kitano and Hideo Hosono

Catalysts 2021, 11(10), 1154; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11101154 - 26 Sep 2021

Viewed by 1994

Abstract

In 2012, we reported that C12A7 electride (C12A7: e⁻) significantly promotes the catalytic activity of Ru nanoparticles for ammonia synthesis through the electron donation from the C12A7: e⁻ with a low work function (2.4 eV) to Ru [...] Full article

(This article belongs to the Special Issue Transition Metal Catalysis)

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