First-principles studies of surface oxide formation on Pt electrode

Abstract

Pt and its alloys are used as electrocatalysts in proton-exchange membrane fuel cells (PEMFC). However, existing fuel-cell technologies still have drawbacks, such as instability and dissolution of Pt on the electrodes, especially during the stop-and-go driving of an electric car. Some experiments show that the Pt oxide layer formed during anodic polarization induces the dissolution of Pt atoms upon cathodic polarization. Other experiments show that surface oxide formation may impede the coarsening of Pt grains or particles. But the atomic structure of surface Pt oxide which is just one or two atomic layers thin and how it originates from clean Pt surface are still not very clear. There are already some theoretical studies of bulk and surface Pt oxides. Here we use first-principles calculations to investigate the detailed interfacial structures of Pt/Pt oxide thin films. We also use Nudge Elastic Band method to study the transformation mechanism from Pt + adsorbed O atoms to surface oxide. Finally, combined with a simple thermodynamic model, we try to directly compare the calculations with experimental results.