Rational fabrication of thin-layered NiCo2S4 loaded graphene as bifunctional non-oxide catalyst for rechargeable zinc-air batteries

Abstract Zinc-air batteries are the promising electrochemical energy conversion and storage devices due to their high theoretical energy density, environmental benignity, low cost and safety. Developing high-performing bifunctional catalyst to improve the ORR and OER kinetic is the key issue of the researchable zinc-air battery. In this work, ultra-thin NiCo2S4 nanosheets with reduced graphene oxide hybrid materials (NiCo2S4/RGO) have been successfully developed. The hybrid catalyst shows a unique hierarchical structure with large surface area, which provides the quick transport pathways and abundant active sites for both ORR and OER. Notably, the conversion of oxides to sulfides changes the electrons state of the metal oxides and create more oxygen defective compared with pure NiCo2O4, effectively improving the ORR/OER′ activity. The strong synergistic effect between NiCo2S4 and RGO further facilitating the intrinsic oxygen reaction process. As expected, the NiCo2S4/RGO bifunctional catalysts demonstrate enhanced ORR/OER activity (ΔE: 0.91 V) and stability, along with the high battery performance (262.6 mW cm−2 and 750 chare-discharge cycles). The work open's great application prospects of sulfides in rechargeable zinc-air batteries.