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

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.