Accurately substituting Fe for Ni2 atom in Ni-MOF with defect-rich for efficient oxygen evolution reaction: Electronic reconfiguration and mechanistic study

Designing metal-organic framework (MOF) with controllable lattice defects and oxygen vacancies is of great significance for effective oxygen evolution reaction (OER). We achieved controlled lattice defects and generated oxygen vacancies in the Ni-MOF nanoflowers by accurately substituting Fe atoms for Ni2 atoms. The optimized Ni0.67Fe0.33-MOF/CFP exhibits remarkable OER performance (an ultra-low overpotential of 281 mV at 100 mA cm-2 and a Tafel slope of 38 mV dec-1) and excellent stability (the activity maintains for 80 h at 100 mA cm-2). Importantly, it is revealed that the active species is the Ni0.67Fe0.33-MOF/NiFeOOH complex for OER. Density functional theory (DFT) provides the insightful catalytic mechanism that the Fe atoms and oxygen vacancies are critical in optimizing the d-band center and promoting the dissociation of oxygen-containing intermediates. Our work introduces a strategy for designing defect-rich MOF-based electrocatalysts, opening up new possibilities for efficient OER systems.