MOF@Cellulose Derived Co–N–C Nanowire Network as an Advanced Reversible Oxygen Electrocatalyst for Rechargeable Zinc–Air Batteries

Zn–air battery is a promising energy storage device because of its remarkably high energy density. However, development of affordable oxygen catalysts with high eletrocatalytic activity and excellent durability is of critical importance for the implementation of rechargeable Zn–air batteries. Here, we report a novel synthesis of three-dimensional (3D) Co–N–C nanowire network (NN) and its remarkable electrocatalytic performance as a bifunctional electrocatalyst in rechargeable Zn–air batteries. The carbon nanowire network was derived from cost-effective cellulose, with Co and N heteroatom doping achieved by annealing the self-assembled MOF@amine-modified cellulose under N2. As reported here, the best sample synthesized at 800 °C, referred to as 3D Co–N–C NN-800, demonstrated an oxygen reduction reaction (ORR) onset potential of 1.05 V and oxygen evolution reaction (OER) overpotential of 0.47 V (10 mA cm–2). As a result, a Zn–air battery assembled with 3D Co–N–C NN-800 demonstrates a small voltage gap of 0.8 V between charge and discharge and excellent durability, as evidenced by a minimal decay after 30 h operation (90 cycles, 15 mA cm–2). This study demonstrates a novel design strategy to enhance the electrcatalytic site and its homogeneity via the covalently bonded doping, which could be employed for the further development of bifunctional carbonaceous electrocatalysts.