A Triphasic Bifunctional Oxygen Electrocatalyst with Tunable and Synergetic Interfacial Structure for Rechargeable Zn-Air Batteries

Atomic-scale design of interfacial structure is an intriguing but challenging approach to developing efficient heterogenous catalysts for bifunctional oxygen electrocatalysis. Herein, an exquisite triphasic interfacial structure featuring the encapsulation of FexNi alloy in a graphitic shell with a partial exposure of the FeOy thin-layered surface is manipulated via an electronic modulation strategy. The spontaneous integration of well-crystallized metal alloy, carbon shell with a tunable active FeOy layer, not only guarantees smooth charge transfer across the thin oxide layer, but also generates the synergistic effect at the interface, thus dramatically boosting the intrinsic activity of oxygen catalysis. Benefiting from these attributes, the hybrid catalyst outperforms the commercial noble-metal benchmarks with a higher half-wave potential of 0.890 V for oxygen reduction reaction and lower overpotential of 308 mV at 10 mA cm(-2) for the oxygen evolution reaction in alkaline media. Beyond that, a high-performance rechargeable Zn-air battery is realized with a narrow voltage gap of 0.742 V and excellent cyclability over 500 cycles at 10 mA cm(-2), demonstrating the great potential of the as-developed triphasic electrocatalyst for practical applications.