Lamellar-stacked cobalt-based nanopiles integrated with nitrogen/sulfur co-doped graphene as a bifunctional electrocatalyst for ultralong-term zinc-air batteries

Abstract

Sluggish oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) kinetics inevitably impede the practical performance of rechargeable zinc–air batteries. Thus, combing the structural designability of transition metal-based electrocatalysts with anionic regulation is highly desired. Herein, mesoporous lamellar-stacked cobalt-based nanopiles with surface-sulfurization modification are elaborately designed and integrated with N/S co-doped graphene to build a robust OER/ORR bifunctional electrocatalyst. The lamellar-stacking mode of mesoporous nanosheets with abundant channels accelerates gas–liquid mass transfer, and partial-sulfurization of cobalt-based matrix surface efficiently improves the intrinsic OER activity. Meanwhile, N/S co-doped graphene further reinforces the ORR active sites while providing a stable conductive skeleton. As expected, this composite electrocatalyst delivers considerable bifunctional activity and stability, with an OER overpotential of 323 mV at 10 mA cm−2 and high durability. When applied in zinc–air batteries, remarkable ultralong-term stability over 4000 cycles and a maximum power density of 150.1 mW cm−2 are achieved. This work provides new insight into structure-composition synergistic design of rapid-kinetics OER/ORR bifunctional electrocatalyst for next-generation metal–air batteries.