Hollow Co9S8 spheres-derived polyhedrons uniformly anchored on N, S-doped graphene for efficient oxygen electrocatalysts

Abstract Exploring highly efficient and low-cost bifunctional electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is significant for the development of renewable energy. Here, Co9S8 nanospheres with hollow structure anchored on N and S dual-doped graphene oxide (Co9S8-NSGO) are synthesized by solvothermal strategy. After pyrolyzed, advanced bifunctional electrocatalysts with feature of sea-island architecture of Co9S8 polyhedrons evenly dispersed on N and S co-doped graphene sheets (Co9S8-NSG) are obtained, in which Co9S8 polyhedrons stem from the derivative of Co9S8 nanospheres. Ascribed to large surface area, sea-island structure of uniform dispersion of Co9S8 nanoparticles on graphene, synergistic effect between Co9S8 and graphene and more active sites based N and S doping, the as-prepared Co9S8-NSG catalyst exhibits excellent OER performance with a small overpotential (240 mV at 10 mA cm−2) and satisfactory ORR performance with half-wave potential (0.79 V). Notably, a zinc-air battery using Co9S8-NSG as air cathode shows high peak power density (120 mW cm−2) and outstanding cycling stability (120 h at 10 mA cm−2).