Oxygen evolution and oxygen reduction catalyzed by Fe-Co-Ni ternary metal sulfides for rechargeable zinc-air battery

Further enhancing the electrocatalytic performance of transition metal sulfides for oxygen evolution and oxygen reduction reactions (OER and ORR) is crucial for the development of high-efficiency electrochemical energy devices. Here, the highly efficient iron-doped nickel sulfide/cobalt sulfide heterostructure catalyst (Fe-NiS 2 /CoS 2 ) was successfully prepared via a combination of hydrothermal-sulfidation-reduction strategy. Physical characterizations coupled with electrochemical tests reveal that Fe doping plays a key role in the excellent performance of Fe-NiS 2 /CoS 2 by lowering charge transfer resistance, optimizing electronic structure, and promoting reaction kinetics synergistically. As a result, the Fe-NiS 2 /CoS 2 catalyst exhibits a bifunctional electrocatalytic reactivity with a low ΔE of 0.61 V, surpassing noble-metal-based catalyst and most of the reported iron-related sulfide bifunctional catalysts. Specifically, the catalyst exhibits low overpotentials of 265 mV at 10 mA cm −2 and 381 mV at 100 mA cm −2 for the OER, while maintaining an ORR E 1/2 of 0.88 V. Aqueous zinc-air battery (ZAB) based on Fe-NiS 2 /CoS 2 achieve the specific capacities of 678.5 mAh g Zn −1 and along with 200 h cycling stability. This work provides an effective approach to improving transition metal sulfides, with potential for broader application in OER/ORR-related energy technologies.