MOF spatial confinement effect regulates Co/Fe speciation in CoFe alloy nitride/N-doped carbon for enhanced electrocatalytic overall water splitting

ZIF confinement disperses CoFe nitride uniformly and tunes Co/Fe ratio precisely. • Co/Fe bimetallic coupling lead to synergistic effects for bifunctional HER/OER. • Low overpotentials reach 85 mV (HER@10 mA·cm −2 ) and 273 mV (OER@50 mA·cm −2 ). • Overall water splitting requires 1.59 V at 10 mA·cm −2 with durability over 100 h. CoFe-based materials are considered promising bifunctional catalysts for overall water splitting due to multicomponent synergistic effects. However, unrestricted metal atom migration during high-temperature synthesis causes particle aggregation and excessive Co–Fe interdiffusion, which destroys bimetallic interfacial structures, covers active sites, and hinders electronic modulation, thus limiting catalytic activity and stability. To solve these problems, a ZIF-assisted spatial confinement strategy is adopted herein. The ZIF framework constrains high-temperature atomic migration, alleviates particle coarsening, and weakens metal interdiffusion to maintain intact bimetallic interfacial environments, while exposing sufficient active sites. Further combining carbonization and in-situ nitridation modification, a composite system of CoFe metal nitride and N-doped carbon was prepared, significantly improving the kinetic properties of HER and OER. The optimal catalyst achieves an overpotential of 85 mV for the HER at 10 mA·cm −2 , and 273 mV for the OER at 50 mA·cm −2 , exhibiting superior catalytic performance compared with commercial noble-metal benchmarks. The assembled overall water splitting system requires only 1.59 V at a working current of 10 mA·cm −2 , and can operate stably for 100 h at 50 mA·cm −2 . This work provides a reliable strategy for inhibiting high-temperature structural degradation of CoFe-based catalysts toward high-efficiency and durable electrocatalytic water splitting.