▎ 摘　　要

Palladium (Pd) has received extensive attention as the substitute for platinum to work as efficient catalyst towards the oxygen reduction reaction (ORR) owing to its high intrinsic activity. However, the Pd catalyst usually performs inferior catalytic stability in the practical electrochemical test. Here, we report a novel design of constructing efficient ORR catalyst with Pd/SnO2 heterojunctions uniformly loaded on the reduced graphene oxide sheets (Pd@SnO2/rGO). The highly conductive rGO sheets are beneficial to increase the electron transfers during the ORR process and the SnO2 support can induce tensile-strain and electron-rich features for Pd nanocrystals in the Pd/SnO2 heterojunctions. The electrochemical results illustrate that the Pd@SnO2/rGO catalyst has higher ORR activity compared to commercial Pd/C and shows remarkable catalytic stability with 1 mV of negative shift in half-wave potential over 20000 cycles of accelerated durability tests. Moreover, the Zn-air battery assembled with Pd@SnO2/rGO cathode exhibits a 2.8-fold higher specific capacity than that with Pd/ C cathode.