Enhanced Activity for Oxygen Reduction Reaction on “Pt3Co” Nanoparticles: Direct Evidence of Percolated and Sandwich-Segregation Structures

Abstract

Atomically resolved structures and compositions of Pt alloy nanoparticles were obtained using aberration-corrected high-angle dark field imaging, which was correlated to specific ORR activity based on a Pt surface area. The enhanced specific ORR activity (∼2 times relative to Pt) of acid-treated “Pt₃Co” nanoparticles can be related to composition variations at the atomic scale and the formation of percolated Pt-rich and Pt-poor regions within individual particles. Upon annealing, we show direct evidence of surface Pt sandwich-segregation structures, which correspond to a specific ORR activity ∼4 times relative to Pt.