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The role of sodium surface species on oxygen charge transfer in the Pt/YSZ system

Lookup NU author(s): Dr Naimah Ibrahim, Dr Danai Poulidi, Dr Maria Rivas, Professor Ian Metcalfe

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Abstract

The role of sodium surface species in the modification of a platinum (Pt) catalyst film supported on 8 mol% yttria-stabilised-zirconia (YSZ) was investigated under a flow of 20 kPa oxygen at 400 degrees C. Cyclic and linear sweep voltammetry were used to investigate the kinetics of the oxygen charge transfer reaction. The Pt/YSZ systems of both 'clean' and variable-coverage sodium-modified catalyst surfaces were also characterised using SEM, XPS and work function measurements using the Kelvin probe technique. Samples with sodium coverage from 0.5 to 100% were used. It was found that sodium addition modifies the binding energy of oxygen onto the catalyst surface. Cyclic voltammetry experiments showed that higher overpotentials were required for oxygen reduction with increasing sodium coverage. In addition. sodium was found to modify oxygen storage and/or adsorption and diffusion increasing current densities at higher cathodic overpotential. Ex situ XPS measurements showed the presence of sodium hydroxide, carbonate and/or oxide species on the catalyst surface, while the Kelvin probe technique showed a decrease of approximately 250 meV in the work function of samples with more than 50% sodium coverage (compared to a nominally 'clean' sample). (C) 2012 Elsevier Ltd. All rights reserved.

Publication metadata

Author(s): Ibrahim N, Poulidi D, Rivas ME, Baikie ID, Metcalfe IS

Publication type: Article

Publication status: Published

Journal: Electrochimica Acta

Year: 2012

Volume: 76

Pages: 112-119

Print publication date: 01/08/2012

Date deposited: 28/03/2013

ISSN (print): 0013-4686

ISSN (electronic): 1873-3859

Publisher: Pergamon

URL: http://dx.doi.org/10.1016/j.electacta.2012.04.160

DOI: 10.1016/j.electacta.2012.04.160

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