Molten-salt-mediated synthesis: Engineering Fe single-atom sites on HKUST-1-derived carbon for efficient oxygen reduction reaction

Nitrogen-doped carbon materials derived from metal–organic frameworks (MOFs) are promising catalysts for the oxygen reduction (ORR), yet their performance still lags behind Pt-based catalysts. While Fe–N–C materials are among the most promising alternatives, achieving high-density and accessible Fe–N x sites remains challenging. Herein, we report a combined molten salt (NaCl) and pyrolysis strategy to transform Cu-based HKUST-1 into a highly active Fe single-atom catalyst (Fe/N–C). The NaCl template enables the concurrent construction of a porous framework and the regulation of surface metal composition. It simultaneously facilitates the substantial removal of Cu species and the stabilization of anchored Fe single atoms on the catalyst surface. This process is further enhanced by melamine as an additional nitrogen source, which maximizes the formation of accessible Fe–N 4 moieties. The resulting Fe/N–C catalyst exhibits outstanding ORR activity in alkaline medium, with a half-wave potential of 0.91 V vs. RHE, along with good stability. Furthermore, a liquid zinc-air battery using this Fe/N–C catalyst as the cathode demonstrated satisfactory performance, achieving a peak power density of 106 mW cm −2 . The resulting clean-surface, iron-centric catalyst demonstrated good ORR activity and stability, validating the effectiveness of this synergistic copper-evaporation and iron-anchoring approach.