Ionic liquid meets ZnIn₂S₄: Synergistically tuning coordination environment of ZnIn₂S₄ grown on porous carbon by N, F doping and S-vacancies to load high concentration of single-atom Sb for efficient flexible Zn-Air batteries

Currently, the improvement in energy efficiency of catalysts for Zn-air batteries (ZABs) is seriously hindered by kinetic retardation. In this study, an ionic liquid was employed to generate sulfur vacancies, nitrogen/fluorine atoms, and a high concentration of single-atom Sb on a layered ZnIn₂S₄ substrate via a one-step synthesis process. These components were uniformly loaded onto porous carbon (Sb_SANF-ZnIn₂S_4-x/PC). The sulfur vacancies and nitrogen/fluorine atoms altered the surface charge distribution of ZnIn₂S_4-x and created an ideal coordination environment for the adsorption of single-atom Sb, enhancing the reactions in oxygen evolution/reduction reactions (OER/ORR) and ZABs. During testing, Sb_SANF-ZnIn₂S_4-x/PC demonstrated a half-wave potential of 0.892 V in ORR and an overpotential of 0.319 V in OER. When assembled into ZABs, it showed a specific capacity of 812.1 mAh g⁻¹ and a power density of 186.2 mW cm⁻². Overall, this study presents a promising one-step synthesis approach for creating a highly efficient electrocatalyst with single-metal atoms, non-metal atoms, and vacancies.