Alloying Effects of Co-Sputtered Gold-Platinum Thin Films on the Oxygen Reduction Reaction in Acidic Electrolyte

Abstract

Co-sputtering was utilized to form metastable solid solution Au/Pt alloy films across the entire range of possible compositions. Homogeneous mixing was achieved without nanoparticle geometries, thereby isolating the effects of alloying from nanoscale size effects on the oxygen reduction reaction (ORR). Furthermore, as-deposited near-surface compositions determined by XPS were within 10% of the bulk compositions determined by EDS indicating that extensive Au surface segregation was avoided by room temperature deposition. The alloys were electrochemically characterized via cyclic voltammetry in Ar-saturated 0.5 M H2SO4 and ORR activity and stability was investigated after O2 saturation under oxidizing potentials. Compositions within the miscibility gap were found to be more electrocatalytic for O2 reduction than the pure Pt film. However, intermediate compositions lacked stability with continuous potential cycling when compared to compositions near the edges of the gap which retained enhanced activity.