Towards Deeper Understanding of the Kinetics of the Electrooxidation of Platinum

Pt catalysts are still the only practical cathode material in proton-exchange membrane fuel cells (PEMFC) despite their limited long-term stability, which results from irreversible surface restructuring and Pt dissolution upon oxidation/reduction. Understanding these processes is mandatory for increasing the lifetime. Our previous studies on Pt(111) and Pt(100) revealed the mechanism by which Pt atoms are extracted from the surface during the initial stages of oxidation. However, the relationship between the electrochemical charge transfer that is required for the formation of surface oxide species and restructuring of the Pt surface is still unknown. We here propose to disentangle these processes by systematic studies of the oxidation/reduction kinetics on Pt(111) and Pt(100) on the millisecond time scale. In these studies, we will monitor the Pt extraction and charge transfer by operando high energy X-ray surface diffraction (HESXRD) and simultaneous electrochemical measurements.