Bifunctional oxygen electrocatalysis on ultra-thin Co9S8/MnS carbon nanosheets for all-solid-state zinc–air batteries

Abstract

The development of high-efficiency and durable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts as air cathodes is still a challenge in energy storage and conversion. In this work, we report two-dimensional (2D) ultra-thin Co₉S₈/MnS sulfur/nitrogen co-doped carbon nanosheets (Co₉S₈/MnS-USNC) with outstanding ORR and OER activities as well as remarkable stability in alkaline media. Benefiting from the accessible functional surface and active sites of the 2D structure and adjustment of the electronic structure by the synergetic effect, Co₉S₈/MnS-USNC possesses a half-wave potential of 0.90 V for the ORR and a low overpotential of 360 mV for the OER at a current density of 10 mA cm⁻². The aqueous zinc–air batteries displayed a maximum power density of 146 mW cm⁻² and superior durability of 600 hours, and those of all-solid-state zinc–air batteries are 79 mW cm⁻² and 18 hours respectively. The reaction mechanism of the Co₉S₈/MnS-USNC catalyst as the air cathode was also verified by in situ Raman spectroscopy.