Evolution of Pt and Pt-Alloy Catalytic Surfaces Under Oxygen Reduction Reaction in Acid Medium

We review our recent work that employs a series of computational techniques including density functional theory, ab initio molecular dynamics, and classical molecular dynamics to investigate changes in the structure and electronic properties of Pt-based alloy catalysts under oxygen reduction reaction conditions in acid medium. We show density-functional theory-based correlations between surface segregation and the oxidation state of the subsurface atoms, and their effects on metal dissolution. Since the onset of Pt dissolution coincides with that of surface oxidation, surface reconstruction phenomena is evaluated using ab initio and classical molecular dynamics at increasing degrees of oxidation on extended surfaces and nanoparticles, including the effects of water and an acidic solution. Significant reconstruction and compositional changes are observed as the surface is modified by the presence of adsorbates and electrolyte components. Finally we discuss the consequences of dealloying and suggest an explanation for the enhanced activity observed experimentally in the resultant nanoporous structures.