Engineering of Co3O4@Ni2P heterostructure as trifunctional electrocatalysts for rechargeable zinc-air battery and self-powered overall water splitting

Rational design of highly efficient, robust and nonprecious electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is highly demanded and challenging. Here, heterostructural Co3O4@Ni2P arrays with numerous reaction sites, unique interfacial electronic structure and fast charge transfer kinetics are developed as electrocatalysts for rechargeable Zn-air batteries and overall water splitting. Both density functional theory calculation and X-ray absorption fine structure analysis manifest that the synergistic structural and abundant electronic modulations interfaces are formed, thus simultaneously promoting the electrocatalytic kinetics, activities and stabilities. Specifically, it can achieve an ultralow overpotential of 270 mV and 28 mV at 10 mA cm−2 for OER and HER, respectively. The water electrolyzer delivers a current density of 10 mA cm−2 at 1.563 V; furthermore, rechargeable Zn-air batteries triggered by this heterostructure can achieve excellent cyclic stability of 177 h (2 h per cycle) at 10 mA cm−2; both devices are superior to the Pt/C + Ir/C. This work not only designs an efficient trifunctional electrocatalyst but also paves an avenue to understand the heterostructure engineering for catalysts development and disclose the underlying relationship of interfacial electronic structures and catalytic properties.