Three-phases Co/Co9S8/MnS heterostructures engineering for boosted ORR/OER activities in Zn–air batteries

Breakthroughs in the design of robust bifunctional oxygen reduction/evolution reaction (ORR/OER) catalysts could put Zn–air batteries performance to the summit but remain full of challenges. In this work, the MnS phase was deliberately introduced into the Mott–Schottky Co/Co 9 S 8 for engineering a three-phases Co/Co 9 S 8 /MnS heterojunction on defect-rich N-doped mesoporous carbon substrate (Co/Co 9 S 8 /MnS-NMC). It affords abundant three-phases heterostructure interfaces that effectively accelerate the electron transfer and trigger further electronic structure reconfiguration, thus advancing the bifunctional ORR/OER activities. Benefiting from these structures, the Co/Co 9 S 8 /MnS-NMC possesses a half-wave potential of 0.84 V toward ORR and a low overpotential of 330 mV toward OER at a current density of 10 mA/cm 2 , catching up with those of commercial Pt/C and RuO 2 catalysts. It also endows the Zn–air batteries with a good power density, round-trip efficiency, and robust stability over 750 h, showcasing the promising potential in practical applications. This work not only provides a facile strategy to construct the three-phases heterojunction catalysts but also sheds light on developing the efficient and robust nonprecious metal-based bifunctional ORR/OER catalysts.