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

Abstract

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 (ΔE) 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.