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Isolating the contributions of surface Sn atoms in the bifunctional behaviour of PtSn CO oxidation electrocatalysts

Isolating the contributions of surface Sn atoms in the bifunctional behaviour of PtSn CO oxidation electrocatalysts
Isolating the contributions of surface Sn atoms in the bifunctional behaviour of PtSn CO oxidation electrocatalysts

The bifunctional mechanism is well-acknowledged for the promoted CO oxidation on Pt-based bimetallic electrocatalysts. However, the direct identification of the active oxygenated species and the nature and electrochemistry of the second component are still a matter of debate. Herein, Snad-Pt/C catalysts, where Sn ad-atoms are exclusively on the surface of Pt nanoparticles at low coverages ranging from 0.0033 to 0.2 monolayers to avoid sub-surface Sn and alloy formation, were prepared as a model system to resolve these issues using a surface organometallic chemistry approach. Effects of the Sn ad-atoms on CO oxidation were studied by CO stripping voltammograms as a function of Sn coverage. Using in situ XAS measurements, the Sn average oxidation state is estimated to increase from +0.2 to +3.1 as the potential increases from 0 to 0.8 VRHE, with the number of the oxygen neighbours increasing stepwise. Pt4.5-Sn-(OH)1.5 is revealed as the active species responsible for the bifunctional mechanism at low overpotentials and is generated via a redox couple corresponding to Pt4.5-Sn*/Pt4.5-Sn-(OH)1.5.

Ad-atoms, Bifunctional mechanism, CO oxidation, In situ XAS, Pt-Sn
0013-4686
Huang, Haoliang
132a8eda-b800-4fa7-9583-6b4306f30247
Blackman, Oliver F.
e8eba065-a096-48e9-82df-b9d8201d269f
Celorrio, Veronica
7a8ccfa9-5d90-4502-8008-5e1bb15035c5
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169
Huang, Haoliang
132a8eda-b800-4fa7-9583-6b4306f30247
Blackman, Oliver F.
e8eba065-a096-48e9-82df-b9d8201d269f
Celorrio, Veronica
7a8ccfa9-5d90-4502-8008-5e1bb15035c5
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169

Huang, Haoliang, Blackman, Oliver F., Celorrio, Veronica and Russell, Andrea E. (2021) Isolating the contributions of surface Sn atoms in the bifunctional behaviour of PtSn CO oxidation electrocatalysts. Electrochimica Acta, 390, [138811]. (doi:10.1016/j.electacta.2021.138811).

Record type: Article

Abstract

The bifunctional mechanism is well-acknowledged for the promoted CO oxidation on Pt-based bimetallic electrocatalysts. However, the direct identification of the active oxygenated species and the nature and electrochemistry of the second component are still a matter of debate. Herein, Snad-Pt/C catalysts, where Sn ad-atoms are exclusively on the surface of Pt nanoparticles at low coverages ranging from 0.0033 to 0.2 monolayers to avoid sub-surface Sn and alloy formation, were prepared as a model system to resolve these issues using a surface organometallic chemistry approach. Effects of the Sn ad-atoms on CO oxidation were studied by CO stripping voltammograms as a function of Sn coverage. Using in situ XAS measurements, the Sn average oxidation state is estimated to increase from +0.2 to +3.1 as the potential increases from 0 to 0.8 VRHE, with the number of the oxygen neighbours increasing stepwise. Pt4.5-Sn-(OH)1.5 is revealed as the active species responsible for the bifunctional mechanism at low overpotentials and is generated via a redox couple corresponding to Pt4.5-Sn*/Pt4.5-Sn-(OH)1.5.

Text
SOMC_EchemActa_v2 - Accepted Manuscript
Restricted to Repository staff only until 10 September 2022.
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Accepted/In Press date: 17 June 2021
Published date: 10 September 2021
Additional Information: Funding Information: The XAS data were collected at Diamond on B18 as part of the UK Catalysis Hub BAG allocation (SP19850–4, SP19850–5 and SP19850–6). We thank Fredrik Hage and Quentin Ramasse for instrument access and the STEM measurements. SuperSTEM is the UK National Research Facility for Advanced Electron Microscopy, supported by the Engineering and Physical Sciences Research Council (EPSRC). HH acknowledges Fellowship support from the China Scholarship Council ( 201608440295 ) and the University of Southampton . Publisher Copyright: © 2021 Copyright: Copyright 2021 Elsevier B.V., All rights reserved.
Keywords: Ad-atoms, Bifunctional mechanism, CO oxidation, In situ XAS, Pt-Sn

Identifiers

Local EPrints ID: 450838
URI: http://eprints.soton.ac.uk/id/eprint/450838
ISSN: 0013-4686
PURE UUID: 601ad0da-752b-49f5-98da-1a9e638f5a0f
ORCID for Andrea E. Russell: ORCID iD orcid.org/0000-0002-8382-6443

Catalogue record

Date deposited: 13 Aug 2021 16:59
Last modified: 28 Apr 2022 01:43

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Contributors

Author: Haoliang Huang
Author: Oliver F. Blackman
Author: Veronica Celorrio

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