Tunable dual cationic redox couples boost bifunctional oxygen electrocatalysis for long-term rechargeable Zn-air batteries.

Efficient nonprecious bifunctional electrocatalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential for improving the electrochemical performance of Zinc-air (Zn-air) batteries. Herein, we report a cobalt-doped Mn(OH)VO catalyst prepared by facile hydrothermal method, and the ratios of cationic redox couples of catalysts were tuned with different Co doping amounts. The as-prepared MnCo(OH)VO (MnCoVO-1) catalyst achieves the highest ratio of (MnMn)/Mn and Co/Co redox couples which serve as ORR and OER active sites respectively, and exhibits the enhanced electrocatalytic performance. Furthermore, when employed as air-cathode catalyst for rechargeable Zn-air batteries, the MnCoVO-1 catalyst reveals a high power density (278 mW cm), enhanced rate performance and outstanding long-term stability of over 270 h. This work demonstrates the Co-doped Mn(OH)VO with optimized electronic structure by rational doping engineering can serve as a promising bifunctional catalyst for oxygen electrocatalysis and rechargeable Zn-air batteries.