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In Situ EPR Study of the Redox Properties of CuO–CeO 2 Catalysts for Preferential CO Oxidation (PROX)

Wang, F; Büchel, R; Savitsky, A; Zalibera, M; Widmann, D; Pratsinis, SE; Lubitz, W; (2016) In Situ EPR Study of the Redox Properties of CuO–CeO 2 Catalysts for Preferential CO Oxidation (PROX). ACS Catalysis , 6 (6) pp. 3520-3530. 10.1021/acscatal.6b00589. Green open access

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Abstract

Understanding the redox properties of metal oxide based catalysts is a major task in catalysis research. In situ electron paramagnetic resonance (EPR) spectroscopy is capable of monitoring the change of metal ion valences and formation of active sites during redox reactions, allowing for the identification of ongoing redox pathways. Here in situ EPR spectroscopy combined with online gas analysis, supported by ex situ X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), temporal analysis of product (TAP), and mass spectrometry (MS) studies, was utilized to study the redox behavior of CuO–CeO2 catalysts under PROX conditions (preferential oxidation of carbon monoxide in hydrogen). Two redox mechanisms are revealed: (i) a synergetic mechanism that involves the redox pair Ce4+/Ce3+ during oxidation of Cu0/Cu+ species to Cu2+ and (ii) a direct mechanism that bypasses the redox pair Ce4+/Ce3+. In addition, EPR experiments with isotopically enriched 17O2 established the synergetic mechanism as the major redox reaction pathway. The results emphasize the importance of the interactions between Cu and Ce atoms for catalyst performance. With the guidance of these results, an optimized CuO–CeO2 catalyst could be designed. A rather wide temperature operation window of 11 K (from 377 to 388 K), with 99% conversion efficiency and 99% selectivity, was achieved for the preferential oxidation of CO in a H2 feed.

Type: Article
Title: In Situ EPR Study of the Redox Properties of CuO–CeO 2 Catalysts for Preferential CO Oxidation (PROX)
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/acscatal.6b00589
Publisher version: http://dx.doi.org/10.1021/acscatal.6b00589
Language: English
Additional information: Copyright © 2016 American Chemical Society. This is the author accepted manuscript version of the article published by the American Chemical Society in ACS Catalysis and available at http://dx.doi.org/10.1021/acscatal.6b00589
Keywords: CuO−CeO2 catalyst; in situ spectroscopy; EPR; redox mechanism; preferential CO oxidation
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/1492818
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