Electrochemical Reduction Reconstruction of Fe3O4-Based Nanocatalysts for Enhanced Oxygen Evolution Reaction

Finding effective electrocatalysts from earth-abundant materials for water splitting is crucial for advancing the future hydrogen economy. Fe-based oxides have been identified as highly efficient transition-metal electrocatalysts for the oxygen evolution reaction (OER). However, their performance is hindered by inappropriate intermediate binding, low intrinsic conductivity, and poor stability, preventing them from competing with precious metal catalysts. This study presents an effective electrochemical reduction strategy for incorporating oxygen vacancies in situ into Fe₃O₄/iron foam (IF) nanocatalysts by applying a constant negative voltage. The results indicate that the reduced Fe₃O₄/IF (referred to as Re-Fe₃O₄/IF) exhibits enhanced OER performance due to the increased oxygen vacancy, substantial electron transfer rate, and greater electrochemically active surface area. Subsequently, this strategy was applied to Ni element-doped iron oxides with electron redistribution, achieving excellent OER performance. The electrochemically optimized Re-Ni_0.8Fe_2.2O_4–x/IF nanocatalyst demonstrates a low overpotential of 239 mV at 100 mA cm^–2, a small Tafel slope of 41.78 mV dec^–1, and an exceptional long-term electrolysis stability of 300 h under alkaline conditions. This study presents a simple and promising approach to induce oxygen vacancies into transition-metal oxides (TMOs)-based OER nanocatalysts for efficient water-splitting systems.