Optimized heterostructure of FeS/Ni3S2 enabling robust oxygen evolution reaction for Zn-Air batteries

Construction heterointerfaces of transition metal sulfides is an effective strategy to enhance the catalytic activity of oxygen evolution reaction (OER) by modulating their electronic structures. Further, incorporating these sulfides with a carbon-based support can improve their catalytic stability by preventing metal active site demetallization and dissolution. Herein, we utilized a combined hard template-pyrolysis method to construct heterostructure of FeS and Ni3S2 encapsulated in N-doped carbon (FeS/Ni3S2-x/NC) and optimized the heterostructure by adjusting the Fe and Ni precursor ratio. Largely exposed FeS/Ni3S2 heterointerfaces enabled a high OER catalytic activity. Especially, the optimized heterostructure of FeS/Ni3S2-2/NC with a larger electrochemical active area and more activity sites (Ni3+) afforded a small OER overpotential of 270 mV at 10 mA cm−2, and exhibited a negligible voltage loss for 35-hour operation at 10 mA cm−2. Furthermore, FeS/Ni3S2-2/NC was employed in rechargeable zinc-air batteries as the air cathode, displaying a superior charge performance and operational stability over 300 h at 5 mA cm−2. This work provides a promising design and engineering strategy for transition metal sulfides as effective OER catalysts.