Dual-molten-salt engineering of accessible active sites in single-atom Fe-N-C catalysts

Abstract

We report a dual-molten-salt strategy to address the limited accessibility of ZIF-8-derived single-atom sites. NaCl preserves the microporous framework, while KCl promotes structural opening to generate a hierarchical micro–mesoporous network. This synergy increases the accessible Fe-Nx site density to 4.0 × 1019 sites g-1 and the utilization to 27%, together with enhanced intrinsic activity for electrocatalytic oxygen reduction.