Screening Spinel Oxide Supports for RuO2 to Boost Bifunctional Electrocatalysts for Advanced Zn–Air Batteries

Abstract The compositing strategy offers great potential in designing bifunctional oxygen electrocatalysts for Zn–air batteries. Recent reports reveal that the couple of RuO 2 , serving as a benchmark oxygen evolution reaction (OER) catalyst, with other oxygen reduction reaction (ORR) catalysts is a wise choice to build highly efficient bifunctional electrocatalysts. However, the design criteria for ORR and OER activities of RuO 2 ‐based composite catalysts are still unclear. Herein, a series of transition metal (Fe, Co, Mn, and Ni)‐doped spinel oxides are designed to support RuO 2 nanorods for exploring the reaction mechanism. Through advanced technology, it is considered that increasing the content and binding energy of Co 3+ and enhancing the oxidation state of Ru 4+ is an efficient strategy to promote ORR and OER activities for RuO 2 /Co‐based spinel oxide composite catalysts. It is found that coupling Mn‐doping Co 3 O 4 (CMO) supports with RuO 2 can induce the highest catalytic activities in ORR/OER and excellent performance in rechargeable Zn–air batteries. Operando electrochemical impedance spectroscopy and theoretical calculation further prove the synergistic effect between RuO 2 and CMO supports originated from the oxygen overflow to overcome the large barrier for oxygen desorption on RuO 2 during OER and oxygen adsorption on CMO supports during ORR.