Lattice-mismatch-induced growth of ultrathin Pt shells with high-index facets for boosting oxygen reduction catalysis

Abstract

Owing to its high catalyzing nature, Pt holds great promise as an efficient catalyst for the oxygen reduction reaction (ORR). Although surface steps/kinks have been proven beneficial for the catalytic performance, constructing steps/kinks on Pt surfaces remains a big challenge due to the high surface energy. Herein, we demonstrate that the lattice mismatch can induce the growth of Pt shells with high-density steps on substrates. We exemplify it by depositing Pt shells on Pd–Cu alloy nanocubes, between which the lattice mismatch reaches 4.53%, and testing the resulting catalysts for the ORR. We show that Pt shells on Pd–Cu alloy nanocubes exhibit an extraordinary increase in both specific and mass activities of 32 and 16 times, respectively, as compared to the commercial Pt/C catalyst. Meanwhile, functional tests in proton exchange membrane fuel cells exhibit a 121.9 mW cm⁻² increase in power density for Pd–Cu@Pt compared to the commercial Pt/C catalyst. Our result indicates that lattice mismatch between Pt shells and Pd–Cu alloy cores plays a key role in forming surface steps, while Pt shells grown on Pd cores only cause the formation of Pd@Pt nanocubes without surface steps. This work suggests that lattice mismatch can serve as an efficient parameter for preparing ORR catalysts with excellent activity and durability.