Engineered spin state in Ce doped LaCoO3 with enhanced electrocatalytic activity for rechargeable Zn-Air batteries

Simultaneously engineering the eg electron filling and increasing the intrinsic conductivity is the bottleneck problem in improving the oxygen electrocatalysis of LaCoO3-based electrocatalysts. Herein, we report the highly enhanced oxygen evolution and reduction reaction (OER/ORR) performance in Ce-doped LaCoO3 electrocatalysts: both theoretical and experimental results indicate that the promoted electrocatalytic activity can be ascribed to the spin state of the Co3+ transition from the low-spin state (LS) to the intermediate-spin state (IS) due to the Ce doping, which subsequently results in a synergistic effect between the enlarged Co 3d-O 2p covalency and improved electrical conductivity. As a result, 5.6 at. % Ce-doped LaCoO3 revealed the most outstanding bifunctional OER/ORR electrocatalytic performance, with a low potential difference of approximately 0.96 V. Furthermore, the assembled rechargeable aqueous Zn-air battery (ZnAB) exhibited an ultrahigh energy density of 963 mA kg−1 and excellent durability without significant decay after 160 h. The constructed all-solid-state ZnABs also revealed good discharge rate activity and a flexible nature. This finding provides a novel design strategy for perovskite oxides for a wide range of applications in high-efficiency rechargeable ZnABs.