Sulfur-modulated FeNi nanoalloys as bifunctional oxygen electrode for efficient rechargeable aqueous Zn-air batteries

Currently, FeNi nanoalloys have received considerable attention for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable aqueous zinc (Zn)-air batteries (ZABs) because of their high content and good chemical stability. However, their poor electronic conductivity, small surface area, and sluggish activity seriously hinder their catalytic performance. Herein, S-modulated FeNi nanoalloys supported by hierarchically porous carbon (S-FeNi/PC) are synthesized through the thermal treatment of metal-organic precursors for efficient bifunctional oxygen catalysis. S decoration endows S-FeNi/PC with a superior OER performance while maintaining an ORR performance that is comparable to that of Pt/C. Hence, S-FeNi/PC exhibits excellent bifunctional oxygen catalytic activity, outperforming the noble-metal-based composite catalysts of Pt/C and RuO2. Notably, the ZABs assembled with S-FeNi/PC exhibit high specific capacity (792 mA h g−1), high peak power density (123.5 mW cm−2), and remarkable durability for 700 charge/discharge cycles at 10 mA cm−2, which surpasses the performance of commercially available Pt/C-RuO2 and other catalysts in previously reported studies. This study will provide not only new bifunctional oxygen electrodes for efficient ZAB devices but also new insights into the design of FeNi-based materials for a wide range of catalytic applications.