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

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.