Synthesis-route-regulated structural and electronic evolution of Fe-doped Co3O4 toward enhanced oxygen evolution reaction

Abstract

As a clean and renewable energy source, the efficient production of hydrogen is crucial for the development of the hydrogen economy. Water electrolysis is an ideal route for green hydrogen production; however, the sluggish kinetics of the anodic oxygen evolution reaction (OER) severely limit the overall efficiency. Although precious metal catalysts exhibit excellent performance, their high cost and scarcity hinder large-scale applications. Despite the advantages of low cost and high stability that make Co₃O₄ a promising alternative, its catalytic performance still needs improvement. This study employed both alkaline chemical precipitation and acidic redox precipitation methods to successfully synthesize iron-doped cobalt oxide catalysts. Electrochemical measurements demonstrated that iron doping effectively enhances the oxygen evolution reaction performance of the material. It was further revealed that the sample prepared via the alkaline chemical precipitation method exhibited superior activity, requiring an overpotential of only 311 mV to achieve a current density of 10 mA cm⁻² and displaying a Tafel slope of 85 mV dec⁻¹. Through a series of characterizations, it was confirmed that, compared to the acidic redox precipitation method, the iron-doped cobalt oxide catalyst prepared by the alkaline chemical precipitation method exhibits superior crystallographic structure. This structure effectively regulates the d-band center position, bringing it closer to the Fermi level, thereby enhancing the adsorption of oxygen-containing intermediates. This adjustment reduces the oxygen evolution reaction energy barrier and optimizes the reaction pathway. The combined optimization of the crystallographic structure and electronic structure significantly improves the electrocatalytic performance of the material and reduces mass transfer resistance during the reaction process.