Eliminating Dissolution of Pt-based Electrocatalysts at the Atomic Scale

28 A remaining challenge for deployment of proton-exchange membrane fuel cells is the 29 limited durability of Pt-nanoscale materials that operate at high voltages during the 30 cathodic oxygen reduction reaction. In this work, atomic-scale insight into well-defined 31 single crystalline, thin-film, and nanoscale surfaces exposed Pt dissolution trends that 32 governed the design and synthesis of durable materials. A newly defined metric, intrinsic 33 dissolution, is essential to understanding the correlation between the measured Pt loss, 34 surface structure, size and ratio of Pt-nanoparticles in carbon support. It was found that 35 utilization of Au underlayer promotes ordering of Pt surface atoms towards (111)36 structure, while Au on the surface selectively protects low-coordinated Pt sites. This 37 mitigation strategy was applied towards 3 nm Pt3Au/C nanoparticles, resulting in 38 elimination of Pt dissolution in liquid electrolyte, including 30-fold durability improvement 39 vs. 3 nm Pt/C over extended potential range up to 1.2 V. 40