We investigated the influence of oxygen on the dissolution of platinum in acidic electrochemical environments, which is closely related to the degradation of the cathodes in operating polymer electrolyte fuel cells (PEFCs), by using carbon-supported platinum nanoparticles (Pt/C), bulk polycrystalline Pt electrodes, and Pt(111) single crystals. We found that the platinum dissolution under potential cycling was significantly enhanced by the presence of oxygen even in the lower potential regions (OH adsorption potentials under inert atmospheres): the amount of dissolved platinum increased by factors of 1.2, 18, and 19 on the Pt/C, polycrystalline Pt, and Pt(111) surfaces, respectively, when the potential of the electrodes was cycled under O 2 . The results of electrochemical and electrochemical scanning tunneling microscopy measurements revealed that a few monolayers of the platinum surface were oxidized, and the surface was roughened by the exposure to oxygen, even in the low potential regions, where no surface reconstruction occurs under N 2 . The electrochemical dissolution of such surface oxides most likely enhances the dissolution of the platinum under the potential cycling in an oxygen atmosphere.
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Matsumoto et al. (2011) studied this question.