Hierarchically mesoporous nickel-iron nitride as a cost-efficient and highly durable electrocatalyst for Zn-air battery

Rechargeable Zn-air battery is largely limited by the lack of low-cost and highly efficient bifunctional oxygen catalysts for both oxygen evolution and reduction reactions (OER and ORR). Herein, we report a promising bifunctional electrocatalyst, mesoporous nickel-iron nitride (Ni3FeN), which was synthesized by thermal ammonalysis of hierarchal NiFe layered double hydroxide microspheres. Different from the widely studied carbon/oxide composite catalysts, this metallic nitride does not need carbon as a conducting support, thus avoiding the issue of carbon corrosion at high potentials. The catalysts provide outstanding bifunctional performance with a low overpotential (0.355 V) at 10 mA cm−2, a low Tafel slope (70 mV dec−1) for OER, and a positive half-wave potential (0.78 V) for ORR under alkaline solution. More importantly, it delivers a lower voltage gap between charge and discharge and a better stability over 300 cycles compared to that of the more costly RuO2 air-cathode.