Sulphur modulated Ni3FeN supported on N/S co-doped graphene boosts rechargeable/flexible Zn-air battery performance

Exploring feasible strategy for preparation of sulfur (S) modulated NiFe compounds and meanwhile clarifying the performance promoting mechanism of such catalysts has triggered numerous interest in rechargeable Zinc-air battery research field. Herein, S modulated Ni3FeN supported on N/S co-doped graphene (S-Ni3FeN/NSG) is synthesized via controlling the nitriding process of NiFe disulfides. The beneficial effect of the design strategy and S decoration on electrocatalytic activity are determined and analysed systematacially. The S-Ni3FeN/NSG-700 delivers excellent bifunctional oxygen electrocatalysis performance with half-wave potential of 0.878 V for ORR and low OER overpotential of 260 mV at 10 mA cm−2. Density Functional Theory (DFT) calculations demonstrate that S decoration effectively promotes the formation of OOH* intermediates and observably decreases the maximum of change of the Gibbs free energies for four primitive OER steps. Notably, when S-Ni3FeN/NSG-700 as air electrode applied in Zn-air battery test, the device shows superb durability for 1200 discharge/charge cycles at 10 mA cm-2. The corresponding all-solid Zinc-air battery exhibits excellent mechanical flexibility and a high power density of 140.1 mW cm-2. Two Zinc-air batteries in series can long-term stably power a self-made water-splitting device. This work provides new insights into highly efficient and low-cost bifunctional oxygen electrocatalyst designing.