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The influence of the oxygen reduction reaction (ORR) on Pt oxide electrochemistry

The influence of the oxygen reduction reaction (ORR) on Pt oxide electrochemistry
The influence of the oxygen reduction reaction (ORR) on Pt oxide electrochemistry
In this study, we employed microelectrodes and scanning electrochemical microscopy (SECM) to investigate the role of molecular oxygen and local pH changes on the electrochemistry of Pt oxide. We show that in acidic media and alkaline conditions, the impact of O 2 is negligible, while in unbuffered neutral media, O 2 strongly affects the formation of Pt oxides. Experiments carried under hindered diffusion reveal that this is due to a high local pH arising from the oxygen reduction reaction. This is evidenced by the appearance, at very positive potentials, of a diffusion controlled wave consistent with the oxidation of OH – . The ORR produces a sufficiently alkaline environment near the electrode to promote the formation of oxide at much more negative potentials than anticipated from the bulk pH. As a result, the onset of oxide formation overlaps the onset of oxygen reduction and it is impossible to obtain a Pt surface free from oxide at potentials positive of the onset of the ORR. Thus, prior exposure of the Pt surface to dissolved oxygen does not leave irreversibly adsorbed oxygen species as previously reported by our group; instead, the ORR induces a coverage of oxide at much lower potentials than determined by the bulk pH.
ORR, Oxygen reduction reaction, PH effects, Pt oxide, SECM, scanning electrochemical microscopy
3525-3532
Rodriguez Martinez, Oliver
db4ea889-5239-4b2b-a744-7c953461b13f
Denuault, Guy
5c76e69f-e04e-4be5-83c5-e729887ffd4e
Rodriguez Martinez, Oliver
db4ea889-5239-4b2b-a744-7c953461b13f
Denuault, Guy
5c76e69f-e04e-4be5-83c5-e729887ffd4e

Rodriguez Martinez, Oliver and Denuault, Guy (2021) The influence of the oxygen reduction reaction (ORR) on Pt oxide electrochemistry. ChemElectroChem, 8 (18), 3525-3532. (doi:10.1002/celc.202100710).

Record type: Article

Abstract

In this study, we employed microelectrodes and scanning electrochemical microscopy (SECM) to investigate the role of molecular oxygen and local pH changes on the electrochemistry of Pt oxide. We show that in acidic media and alkaline conditions, the impact of O 2 is negligible, while in unbuffered neutral media, O 2 strongly affects the formation of Pt oxides. Experiments carried under hindered diffusion reveal that this is due to a high local pH arising from the oxygen reduction reaction. This is evidenced by the appearance, at very positive potentials, of a diffusion controlled wave consistent with the oxidation of OH – . The ORR produces a sufficiently alkaline environment near the electrode to promote the formation of oxide at much more negative potentials than anticipated from the bulk pH. As a result, the onset of oxide formation overlaps the onset of oxygen reduction and it is impossible to obtain a Pt surface free from oxide at potentials positive of the onset of the ORR. Thus, prior exposure of the Pt surface to dissolved oxygen does not leave irreversibly adsorbed oxygen species as previously reported by our group; instead, the ORR induces a coverage of oxide at much lower potentials than determined by the bulk pH.

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20210824_manuscript as accepted - Accepted Manuscript
Restricted to Repository staff only until 24 August 2022.
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20210824_SI as accepted
Restricted to Repository staff only
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More information

Accepted/In Press date: 17 August 2021
e-pub ahead of print date: 24 August 2021
Keywords: ORR, Oxygen reduction reaction, PH effects, Pt oxide, SECM, scanning electrochemical microscopy

Identifiers

Local EPrints ID: 451181
URI: http://eprints.soton.ac.uk/id/eprint/451181
PURE UUID: 3f50e412-de7c-4e06-8f6e-53012c2fcc34
ORCID for Guy Denuault: ORCID iD orcid.org/0000-0002-8630-9492

Catalogue record

Date deposited: 14 Sep 2021 16:07
Last modified: 28 Apr 2022 01:37

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Contributors

Author: Oliver Rodriguez Martinez
Author: Guy Denuault ORCID iD

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