Toward Anticorrosion Electrodes: Site-Selectivity and Self-Acceleration in the Electrochemical Corrosion of Platinum

As an important concern in both science and industry, metal corrosion at solid/liquid interfaces is not well understood at the atomic level. The challenge to investigators lies in the simultaneous consideration of the extended solid surface, the electrochemical potential, and the water solution. The work presented here represents the first theoretical attempt to elucidate the oxidation mechanism of the Pt electrode under electrochemical conditions by exploring the oxidation kinetics of differently structured Pt surfaces, including Pt(111), Pt(211), and Pt(100). We show that the most abundant and close-packed (111) surface in Pt metal can be oxidized because of the presence of surface OH. The corrosion is self-accelerated kinetically once the defects are created, as demonstrated by the low kinetic barrier of oxidation on Pt(211). By contrast, the open Pt(100) facet is very inert toward surface oxidation. Apart from the revealed surface-structure sensitivity, Pt corrosion is also strongly affected by the local oxygen coverage as pinned by the electrochemical potential. For Pt(111), the subsurface oxygen formation occurs only above 0.5 ML oxygen coverage around 1.1 V. The kinetics model for the surface oxidation proposed in this work provides new insights for designing the next generation of anticorrosion electrode materials in fuel cells.