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

Abstract

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 Mn2(OH)3VO3 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 Mn1.8Co0.2(OH)3VO3 (MnCoVO-1) catalyst achieves the highest ratio of (Mn3+Mn4+)/Mn2+ and Co3+/Co2+ 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−2), enhanced rate performance and outstanding long-term stability of over 270 h. This work demonstrates the Co-doped Mn2(OH)3VO3 with optimized electronic structure by rational doping engineering can serve as a promising bifunctional catalyst for oxygen electrocatalysis and rechargeable Zn–air batteries.