Electrochemical Reduction\nReconstruction of Fe<sub>3</sub>O<sub>4</sub>‑Based Nanocatalysts\nfor Enhanced Oxygen\nEvolution Reaction

Finding effective electrocatalysts from earth-abundant\nmaterials\nfor water splitting is crucial for advancing the future hydrogen economy.\nFe-based oxides have been identified as highly efficient transition-metal\nelectrocatalysts for the oxygen evolution reaction (OER). However,\ntheir performance is hindered by inappropriate intermediate binding,\nlow intrinsic conductivity, and poor stability, preventing them from\ncompeting with precious metal catalysts. This study presents an effective\nelectrochemical reduction strategy for incorporating oxygen vacancies\nin situ into Fe<sub>3</sub>O<sub>4</sub>/iron foam (IF) nanocatalysts\nby applying a constant negative voltage. The results indicate that\nthe reduced Fe<sub>3</sub>O<sub>4</sub>/IF (referred to as <i>Re</i>-Fe<sub>3</sub>O<sub>4</sub>/IF) exhibits enhanced OER\nperformance due to the increased oxygen vacancy, substantial electron\ntransfer rate, and greater electrochemically active surface area.\nSubsequently, this strategy was applied to Ni element-doped iron oxides\nwith electron redistribution, achieving excellent OER performance.\nThe electrochemically optimized <i>Re</i>-Ni<sub>0.8</sub>Fe<sub>2.2</sub>O<sub>4–<i>x</i></sub>/IF nanocatalyst\ndemonstrates a low overpotential of 239 mV at 100 mA cm<sup>–2</sup>, a small Tafel slope of 41.78 mV dec<sup>–1</sup>, and an\nexceptional long-term electrolysis stability of 300 h under alkaline\nconditions. This study presents a simple and promising approach to\ninduce oxygen vacancies into transition-metal oxides (TMOs)-based\nOER nanocatalysts for efficient water-splitting systems.