Corrosion Strategy-Induced Undercoordinated Fe Active Sites in NiFe LDH for Alkaline Water Oxidation

The electrochemical restructuring of nickel-iron layered double hydroxide (NiFe LDH) into high-oxidation-state Ni/Fe oxyhydroxide is crucial for the alkaline oxygen evolution reaction (OER). Nevertheless, the sluggish self-reconstruction kinetics including high energy barriers and complex phase-transition dynamics of NiFe LDH significantly restrict its electrocatalytic performances. Herein, an oxygen vacancy-rich NiFe LDH decorated on iron foam (FF) is synthesized through a corrosion strategy. The corrosion process provides undercoordinated active sites in NiFe LDH/FF for OER. In alkaline electrolytes, NiFe LDH/FF displays an exceptional OER activity (a mere 254 mV overpotential with a Tafel slope of 51.7 mV dec^-1) and a remarkable stability over 100 h at 500 mA cm^-2. Comprehensive experimental and theoretical calculations further reveal that NiFe LDH/FF with undercoordinated active sites facilitates electrochemical reconstruction into highly active NiOOH and FeOOH phases against NiFe LDH/nickel foam. The Fe active sites in NiFe LDH/FF can effectively reduce the adsorption strength of oxygen intermediates, thereby altering the rate-determining step from (O^* → OOH^*) to (OH^*→ O^*) and lowering its reaction energy barrier during the OER process. This work presents an innovative strategy for designing low-energy-consumption OER electrocatalysts through a corrosion strategy and defect engineering.