Atomic Rearrangement in Core–Shell Catalysts Induced by Electrochemical Activation for Favorable Oxygen Reduction in Acid Electrolytes

In Pt-based alloy structures, selective leaching out of the non-Pt metal component (known as “dealloying)” improves catalytic activity during operation due to an increase in the electrochemically active surface area. This indicates that in Pt-based alloy structures, an electrochemical stimulus induces structural change, and the non-Pt component plays an important role in determining the catalytic performance. In this study, we prepared highly active and durable Pd@Cu@Pt core–shell catalysts for an acidic oxygen reduction reaction by a facile method and elucidated the correlation between performance improvement and repetitive potential cycling beyond a simple dealloying effect. Electrochemical activation induces the formation of a localized PtCu alloy, which is strongly correlated with excellent catalytic activity and durability (mass activity after durability test: 2.6 A mg^–1_Pt), on the surface and subsurface via atomic rearrangement. The origin of such catalytic activity and durability is determined by synchrotron X-ray spectroscopy, electrochemical analysis, and density functional theory calculations.