Density functional theory study on quasi-three-dimensional oxidized platinum surface: Phase transition between α-PtO₂-like and β-PtO₂-like structures

We investigate the oxidation process of a platinum surface by using the density functional theory approach under the periodic boundary condition. This oxidation process has received much attention because it is an initial step in the dissolution of platinum catalysts in polymer electrolyte fuel cells. In this research, we determine the optimized structure of α -PtO₂-like and β-PtO₂-like oxidized platinum surfaces, which have recently been proposed on the basis of in situ X-ray diffraction analysis, at the Kohn Sham density functional theory (KS-DFT) generalized gradient approximation (GGA) level of theory. We discuss the phase transition from the α-PtO₂-like surface to the β-PtO₂-like surface, including the place-exchange reaction between oxygen and platinum atoms. We propose an intermediate structure in the phase transition, and show that the β-PtO₂-like structure can be formed directly from this intermediate structure.