Journal
ELECTROCHIMICA ACTA
Volume 333, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.electacta.2019.135509
Keywords
Gas-diffusion electrode; Platinum dissolution; Phosphoric acid; Fuel cell; Mathematical modelling
Categories
Funding
- Grant Agency of the Czech Republic [19-02964J]
- Operational Programme Prague - Competitiveness [CZ.2.16/3.1.00/24501]
- National Program of Sustainability [NPU I LO1613]
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This paper presents the experimentally studied degradation of a gas-diffusion electrode under a potentiostatic regime. The experimental conditions corresponded to the operation of a high-temperature fuel cell with a proton-exchange membrane, e.g. in 99.6 wt% H3PO4, at a temperature of 160 degrees C. A onedimensional mathematical model of the degradation of a gas-diffusion electrode was validated using experimental data and utilised for determination of kinetics data of the electrochemical dissolution of Pt. The mathematical model predicted a general mechanism of Pt degradation during electrode polarisation, comprising the electrochemical oxidation of the surface of smaller nanoparticles to PtO, followed by the chemical dissolution of PtO to Pt-(sol)(2+) and electrochemical reduction of the formed Pt-(sol)(2+) on the bare Pt surface of larger nanoparticles. The intensity of degradation varied with the electrode polarisation potential. At potentials close to 0.7 V vs. dynamic hydrogen electrode (DHE), only small nanoparticles were dissolved, while at potentials close to 1 V vs. DHE, Pt dissolution took place on a wider range of nanoparticle sizes, resulting in a higher concentration of Pt-(sol)(2+) on the electrode and, consequently, in a higher rate of nanoparticle growth. The mathematical model presented can be used, with modifications, to make an approximate estimate of the extent of degradation and Pt nanoparticle size distribution in a gas-diffusion cathode, depending on the polarisation potential within the range of 0.7-1 V vs. DHE. (C) 2019 Elsevier Ltd. All rights reserved.
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