Engineering core–shell Co9S8/Co nanoparticles on reduced graphene oxide: Efficient bifunctional Mott–Schottky electrocatalysts in neutral rechargeable Zn–Air batteries

It is significant for the rational construction of the high–efficient bifunctional electrocatalysts for in–depth understandings of how to improve the electron transfer and ion/oxygen transport in catalyzing oxygen reduction reaction and oxygen evolution reaction (ORR and OER), but still full of vital challenges. Herein, we synthesize the novel “three–in–one” catalyst that engineers core–shell Mott–Schottky Co9S8/Co heterostructure on the defective reduced graphene oxide (Co9S8/Co–rGO). The Co9S8/Co–rGO catalyst exhibits abundant Mott–Schottky heterogeneous–interfaces, the well–defined core–shell nanostructure as well as the defective carbon architecture, which provide the multiple guarantees for enhancing the electron transfer and ion/oxygen transport, thus boosting the catalytic ORR and OER activities in neutral electrolyte. As expected, the integrated core–shell Mott–Schottky Co9S8/Co–rGO catalyst delivers the most robust and efficient rechargeable ZABs performance in neutral solution electrolytes accompanied with a power density of 59.5 mW cm−2 and superior cycling stability at 5 mA cm−2 over 200 h. This work not only emphasizes the rational designing of the high–efficient bifunctional oxygen catalysts from the fundamental understanding of accelerating the electron transfer and ion/oxygen transport, but also sheds light on the practical application prospects in more friendly environmentally neutral rechargeable ZABs.