A systematic study of the catalytic durability of Pd@Pt2−3L nano-sized octahedra toward oxygen reduction

Abstract

We have systemically evaluated the catalytic durability of Pd@Pt2−3L octahedra of 21nm in size toward the oxygen reduction reaction (ORR) by examining their elemental, structural, and morphological changes in response to repeated potential cycling between 0.6–1.1VRHE. When supported on carbon, the Pd@Pt2−3L octahedra exhibited greatly improved durability relative to the commercial Pt/C catalyst because of the enlarged particle size (21nm vs. 3nm). The Pd in the core could also be sacrificed during the accelerated durability test to hinder the oxidation and dissolution of Pt in the shell. Even after the Pd cores had been removed up to 10,000 cycles of potential sweeping, the {111} facets on the Pt shells were still well preserved to retain the specific activity at a level of 1.6mAcm−2 (0.9VRHE). Due to the creation of additional catalytic sites on the inner surface, the hollowing out of Pd@Pt2−3L octahedra actually increased the specific electrochemical surface area. As such, the mass activity of the Pd@Pt2−3L/C catalyst kept increasing up to 10,000 cycles of repeated sweeping and then started to decline upon further cycling. In contrast, the mass activity of the Pt/C dropped quickly with repeated potential cycling, which could be largely attributed to severe aggregation of the nanoparticles, as well as the loss of Pt due to detachment and/or dissolution.