Degradation kinetics of Pt during high-temperature PEM fuel cell operation part II: Dissolution kinetics of Pt incorporated in a catalyst layer of a gas-diffusion electrode. (10th February 2020)

• Record Type: Journal Article
• Authors: Prokop, M.; Kodym, R.; Bystron, T.; Drakselova, M.; Paidar, M.; Bouzek, K.
• Is Part Of: Electrochimica acta. Volume 333(2020)
• Publication Date: 2020-02-10
• Subjects: Gas-diffusion electrode -- Platinum dissolution -- Phosphoric acid -- Fuel cell -- Mathematical modelling; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2019.135509
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: 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% H3 PO4, at a temperature of 160 °C. A one-dimensional 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 2+ (sol) and electrochemical reduction of the formed Pt 2+ (sol) 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 2+ (sol) 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. Graphical abstract: Image 108361