Metal Supported Catalysts for Preferential Carbon Monoxide Oxidation (CO-PROX)

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Catalysis in Organic and Polymer Chemistry".

Deadline for manuscript submissions: closed (20 November 2021) | Viewed by 6677

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Inorganic Chemistry Department, University of Alicante, Ap. 99, E03080 Alicante, Spain
Interests: materials science; catalysis; gas pollution control; deNOx; deSoot; deN2O; zeolytes; mixed oxides; monoliths
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Guest Editor
Department of Inorganic Chemistry, University of Alicante, E03080 Alicante, Spain
Interests: Catalysis, environment and energy, surface science, inorganic chemistry, 3D-printing, CO-PROX, cerium oxide, computational chemistry.

Special Issue Information

Dear Colleagues,

A primary challenge facing society is the reduction of atmospheric CO2. Decarbonization of the energy sector is urgent. To this end, the deployment of hydrogen (H2) is promising, especially as inlet feeding for proton exchange membrane (PEM) fuel cells. However, a clean H2 market is dependent on the further development of renewables and, consequently, most of our current hydrogen production relies on natural gas steam reforming (SR). This method features significant CO co-production, leading to a non-stoichiometric H2-rich mixture. For uses demanding purity, the resulting reformate stream must be treated in subsequent refinement processes to achieve the CO clean-up required outputs. After SR, implementing a water–gas shift (WGS) reaction reduces the CO content between 0.5% and 2%. This lower limit cannot be further decreased by thermodynamic restrictions. As a result, current large-scale-produced H2 streams cannot be used directly in PEM fuel cells whose Pt-based electrodes are sensitive to CO poisoning in trace ppm levels. Additional purification steps need to be considered. Since PEM fuel cells are particularly interesting in the transportation sector and in portable applications, the potential miniaturization of the global process is of particular importance when achievable by a suitable catalytic approach.

The preferential CO oxidation (CO-PROX) reaction is widely claimed to be the most promising approach to tackle H2 purification for fuel cell uses. This Special Issue, “Metal Supported Catalysts for the Preferential Carbon Monoxide Oxidation (CO-PROX)”, aims to cover outstanding recent research and novel trends in the design of efficient heterogeneous catalysis in the CO-PROX reaction. Contributions with relevant insights on the underlying fundamental principles based on original experimental and/or theoretical findings are welcome.

Prof. Dr. Agustín Bueno López
Dr. Arantxa Davó Quiñonero
Guest Editors

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Keywords

  • heterogeneous catalysis
  • supported catalysts
  • H2 purification
  • CO-PROX
  • metal oxides
  • PEM fuel cells
  • reaction mechanism

Published Papers (2 papers)

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Research

23 pages, 4109 KiB  
Article
Investigations of the Effect of H2 in CO Oxidation over Ceria Catalysts
by Arantxa Davó-Quiñonero, Sergio López-Rodríguez, Cristian Chaparro-Garnica, Iris Martín-García, Esther Bailón-García, Dolores Lozano-Castelló, Agustín Bueno-López and Max García-Melchor
Catalysts 2021, 11(12), 1556; https://doi.org/10.3390/catal11121556 - 20 Dec 2021
Cited by 4 | Viewed by 2943
Abstract
The preferential CO oxidation (so-called CO-PROX) is the selective CO oxidation amid H2-rich atmospheres, a process where ceria-based materials are consolidated catalysts. This article aims to disentangle the potential CO–H2 synergism under CO-PROX conditions on the low-index ceria surfaces (111), [...] Read more.
The preferential CO oxidation (so-called CO-PROX) is the selective CO oxidation amid H2-rich atmospheres, a process where ceria-based materials are consolidated catalysts. This article aims to disentangle the potential CO–H2 synergism under CO-PROX conditions on the low-index ceria surfaces (111), (110) and (100). Polycrystalline ceria, nanorods and ceria nanocubes were prepared to assess the physicochemical features of the targeted surfaces. Diffuse reflectance infrared Fourier-transformed spectroscopy (DRIFTS) shows that ceria surfaces are strongly carbonated even at room temperature by the effect of CO, with their depletion related to the CO oxidation onset. Conversely, formate species formed upon OH + CO interaction appear at temperatures around 60 °C and remain adsorbed regardless the reaction degree, indicating that these species do not take part in the CO oxidation. Density functional theory calculations (DFT) reveal that ceria facets exhibit high OH coverages all along the CO-PROX reaction, whilst CO is only chemisorbed on the (110) termination. A CO oxidation mechanism that explains the early formation of carbonates on ceria and the effect of the OH coverage in the overall catalytic cycle is proposed. In short, hydroxyl groups induce surface defects on ceria that increase the COx–catalyst interaction, revealed by the CO adsorption energies and the stabilization of intermediates and readsorbed products. In addition, high OH coverages are shown to facilitate the hydrogen transfer to form less stable HCOx products, which, in the case of the (110) and (100), is key to prevent surface poisoning. Altogether, this work sheds light on the yet unclear CO–H2 interactions on ceria surfaces during CO-PROX reaction, providing valuable insights to guide the design of more efficient reactors and catalysts for this process. Full article
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17 pages, 2543 KiB  
Article
Preferential Oxidation of CO over CoFe2O4 and M/CoFe2O4 (M = Ce, Co, Cu or Zr) Catalysts
by Mehdi Béjaoui, Abdelhakim Elmhamdi, Laura Pascual, Patricia Pérez-Bailac, Kais Nahdi and Arturo Martínez-Arias
Catalysts 2021, 11(1), 15; https://doi.org/10.3390/catal11010015 - 25 Dec 2020
Cited by 10 | Viewed by 2979
Abstract
CoFe2O4 prepared by sol-gel has been examined with respect to its catalytic performance for preferential CO oxidation in a H2-rich stream. In turn, the promoting effects of incorporation of Ce, Co, Cu, and Zr by impregnation on the [...] Read more.
CoFe2O4 prepared by sol-gel has been examined with respect to its catalytic performance for preferential CO oxidation in a H2-rich stream. In turn, the promoting effects of incorporation of Ce, Co, Cu, and Zr by impregnation on the surface of CoFe2O4 on the process are examined as well. The catalysts have been characterized by N2 adsorption, X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), temperature programmed reduction (TPR), and X-ray photoelectron spectra (XPS), as well as diffuse reflectance infrared DRIFTS under reaction conditions with the aim of establishing structure/activity relationships for the mentioned catalyst/process. It is shown that while the presence of the various metals on CoFe2O4 hinders a low temperature CO oxidation process, it appreciably enhances the activity above 125 °C. This is basically attributed to the surface modifications, i.e. cobalt oxidation, induced in CoFe2O4 upon introduction of the metals. In turn, no methanation activity is observed in any case except for the copper-containing catalyst, in which achievement of reduced states of cobalt appears most favored. Full article
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