Cu and Co nanoparticle-Co-decorated N-doped graphene nanosheets: a high efficiency bifunctional electrocatalyst for rechargeable Zn-air batteries

It is still a great challenge to explore and reasonably design an efficient, economic and long-term stable oxygen electrochemical reaction catalyst. Therefore, herein, a superiorly active and durable bifunctional electrocatalyst made of copper (Cu) and cobalt (Co) nanoparticle-co-decorated N-doped graphene nanosheets (CuCo@N-C) is reported, which shows the low oxygen reduction reaction/oxygen evolution reaction (ORR/OER) potential gap (E) of 0.65 V; the catalytic activity of CuCo@N-C is promoted by the co-decoration of copper and cobalt nanoparticles due to the strong electron transfer between Cu and Co, enhanced active surface area, and strongly facilitated reaction kinetics. Accordingly, the aqueous Zn-air battery (ZAB) assembled with CuCo@N-C as the air electrode exhibited the high voltage of 1.51 V, the maximum power density of 170 mW cm(-2) (1.48 V and 165 mW cm(-2) for Pt/C, respectively), and excellent device cycling stability. The solid-like ZAB thus constructed showed the low voltage gap of 0.76 V at 40 mA cm(-2) and the high energy efficiency of 72% at 10 mA cm(-2) with an excellent cyclic stability (50 h). In addition to increasing the application potential of ZABs in flexible devices, this study provides a new perception for the correlation between bi-metallic nanoparticles and N-doped graphene and a new avenue for the reasonable design of bifunctional electrocatalysts for ZABs.