Regulation of electronic structure in medium-entropy metal sulfides nanoparticles as highly efficient bifunctional electrocatalysts for zinc-air battery

Medium/high-entropy materials have attracted more and more attention in catalytic field in view of their unique properties, yet the related catalytic mechanisms remain ambiguous. Herein, we demonstrate a two-step method for the preparations of medium-entropy metal sulfides (MESs) nanoparticles through the sulfuration of metal-organic frameworks (MOFs) precursors. Compared with the MOF precursor, MES has better electrocatalytic performance in oxygen evolution and reduction reactions (OER/ORR). Electron energy loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS) characterization indicate that the sulfidation can lead metallic ions to possessing higher valence states. Furthermore, the regulation of electronic structure are further proved by density functional theory (DFT) calculations. Rechargeable zinc-air batteries assembled with the Fe1.2(CoNi)1.8S6 MES nanoparticles catalyst superior performances outperforming the commercial catalyst (Pt/C+RuO2). The reported two-step method of fabrication strategy for preparing medium-entropy metal sulfides may further contribute to fundamental research into and industrial applications of medium-entropy materials in the rechargeable zinc-air batteries.