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Role of SnO2 in the bifunctional mechanism of CO oxidation at Pt-SnO2 electrocatalysts

Role of SnO2 in the bifunctional mechanism of CO oxidation at Pt-SnO2 electrocatalysts
Role of SnO2 in the bifunctional mechanism of CO oxidation at Pt-SnO2 electrocatalysts

Pt-Sn bimetallic catalysts, especially Pt-Sn alloys, are considered highly CO-tolerant and are thus candidates for reformate derived hydrogen oxidation and for direct oxidation of fuel cell molecules. However, it remains unclear if this CO-tolerance originates from Sn in the Pt-Sn alloy or whether SnO2, present as a separate phase, also contributes. In this work, a carbon-supported Pt-SnO2 was carefully synthesized to avoid the formation of Pt-Sn alloy phases. The resulting structure was analysed by scanning transmission electron microscopy (STEM) and detailed X-ray absorption spectroscopy (XAS). CO oxidation voltammograms of the Pt-SnO2/C and other SnO2-modified Pt surfaces unambiguously suggest that a bifunctional mechanism is indeed operative at such Pt-SnO2 catalysts for stable CO oxidation at low overpotentials. The results from these studies suggest that the bifunctional mechanism can be attributed to the co-catalysis role of SnO2, in which the surface hydroxide of SnO2 (Sn-OH) reacts with CO adsorbed on Pt surface (Pt-COads) and regenerates via a SnII/SnIV reversible redox couple (−0.2–0.3 V vs. reversible hydrogen electrode).

bifunctional mechanism, CO oxidation, electrocatalysts, Pt-SnO, SnO
2572-2582
Huang, Haoliang
132a8eda-b800-4fa7-9583-6b4306f30247
Hayes, Edward T.C.
4588961f-f1ff-4b84-ba06-bb8c6719a85e
Gianolio, Diego
5b316f7d-f314-4337-954e-8c0ce8e38223
Cibin, Giannantonio
e2cdeddc-2f78-416e-9507-3894ad3768c9
Hage, Fredrik S.
bed49412-adcf-413a-99de-07edf7e947db
Ramasse, Quentin M.
30aed351-dfed-4eea-9c87-375b75e24b79
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169
Huang, Haoliang
132a8eda-b800-4fa7-9583-6b4306f30247
Hayes, Edward T.C.
4588961f-f1ff-4b84-ba06-bb8c6719a85e
Gianolio, Diego
5b316f7d-f314-4337-954e-8c0ce8e38223
Cibin, Giannantonio
e2cdeddc-2f78-416e-9507-3894ad3768c9
Hage, Fredrik S.
bed49412-adcf-413a-99de-07edf7e947db
Ramasse, Quentin M.
30aed351-dfed-4eea-9c87-375b75e24b79
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169

Huang, Haoliang, Hayes, Edward T.C., Gianolio, Diego, Cibin, Giannantonio, Hage, Fredrik S., Ramasse, Quentin M. and Russell, Andrea E. (2021) Role of SnO2 in the bifunctional mechanism of CO oxidation at Pt-SnO2 electrocatalysts. ChemElectroChem, 8 (13), 2572-2582. (doi:10.1002/celc.202100642).

Record type: Article

Abstract

Pt-Sn bimetallic catalysts, especially Pt-Sn alloys, are considered highly CO-tolerant and are thus candidates for reformate derived hydrogen oxidation and for direct oxidation of fuel cell molecules. However, it remains unclear if this CO-tolerance originates from Sn in the Pt-Sn alloy or whether SnO2, present as a separate phase, also contributes. In this work, a carbon-supported Pt-SnO2 was carefully synthesized to avoid the formation of Pt-Sn alloy phases. The resulting structure was analysed by scanning transmission electron microscopy (STEM) and detailed X-ray absorption spectroscopy (XAS). CO oxidation voltammograms of the Pt-SnO2/C and other SnO2-modified Pt surfaces unambiguously suggest that a bifunctional mechanism is indeed operative at such Pt-SnO2 catalysts for stable CO oxidation at low overpotentials. The results from these studies suggest that the bifunctional mechanism can be attributed to the co-catalysis role of SnO2, in which the surface hydroxide of SnO2 (Sn-OH) reacts with CO adsorbed on Pt surface (Pt-COads) and regenerates via a SnII/SnIV reversible redox couple (−0.2–0.3 V vs. reversible hydrogen electrode).

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Accepted/In Press date: 21 June 2021
Published date: 23 June 2021
Additional Information: Funding Information: HH acknowledges Fellowship support from the China Scholarship Council (201608440295) and the University of Southampton. XAS data were collected at Diamond on B18 as part of the UK Catalysis Hub BAG allocation (SP15151-9 and SP15151-10). SuperSTEM is the UK National Research Facility for Advanced Electron Microscopy, supported by the Engineering and Physical Sciences Research Council (EPSRC). Funding Information: HH acknowledges Fellowship support from the China Scholarship Council (201608440295) and the University of Southampton. XAS data were collected at Diamond on B18 as part of the UK Catalysis Hub BAG allocation (SP15151‐9 and SP15151‐10). SuperSTEM is the UK National Research Facility for Advanced Electron Microscopy, supported by the Engineering and Physical Sciences Research Council (EPSRC). Publisher Copyright: © 2021 Wiley-VCH GmbH Copyright: Copyright 2021 Elsevier B.V., All rights reserved.
Keywords: bifunctional mechanism, CO oxidation, electrocatalysts, Pt-SnO, SnO

Identifiers

Local EPrints ID: 450828
URI: http://eprints.soton.ac.uk/id/eprint/450828
PURE UUID: 301daf4c-254d-4f28-a66e-36c2d338669a
ORCID for Andrea E. Russell: ORCID iD orcid.org/0000-0002-8382-6443

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Date deposited: 13 Aug 2021 16:34
Last modified: 23 Jun 2022 04:01

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Contributors

Author: Haoliang Huang
Author: Edward T.C. Hayes
Author: Diego Gianolio
Author: Giannantonio Cibin
Author: Fredrik S. Hage
Author: Quentin M. Ramasse

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