Bifunctional oxygen electrocatalysis at Co-B,N,S-graphene composite investigated by scanning electrochemical microscopy at variable temperatures and its application in Zn-air battery

Abstract Development of high-efficiency bifunctional oxygen electrocatalyst is evidently demanded in Zn-air batteries. Herein, we report the synthesis of cobalt compounds supported on B-, N- and S-doped graphene (Co-B,N,S-G) via simple hydrothermal method. The as-prepared Co-B,N,S-G exhibited excellent electrocatalytic activity and long-term stability for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Notably, scanning electrochemical microscopy (SECM) was specifically improved to allow the investigation of local ORR and OER reactivity of the Co-B,N,S-G sample at variable temperatures. Practically, the Co-B,N,S-G-based air electrode was used as cathode to construct a Zn-air battery, which presented an extremely small charge/discharge voltage gap of 0.64 V, and remained a high voltage efficiency of 67% after 500 cycles (ca. 84 h). The constructed Zn-air battery was capable of powering LED-figures for at least 30 h. Impressively, the reported work exhibited the feasible prospect of temperature-controlled SECM on evaluating electrocatalysts at submicrometer scale at different temperatures.