Defect-rich (Co, Fe)3O4 hierarchical nanosheet arrays for efficient oxygen evolution reaction

The development of efficient non-precious metal catalysts to accelerate the oxygen evolution reaction (OER) kinetics is important for the development of water-derived hydrogen fuel. Iron-cobalt oxide ((Co, Fe) 3 O 4 ) is one of the most promising transition metal-based OER electrocatalysts under alkaline conditions, but its activity is unsatisfactory due to its limited active sites and poor electronic conductivity. Herein, self-supported (Co, Fe) 3 O 4 hierarchical nanosheet arrays with massive oxygen vacancies (denoted as V O -(Co, Fe) 3 O 4 /CC) are synthesized by a simple reduction method at room temperature. Oxygen vacancies can regulate the ratio of Co 2+ /Co 3+ , which leads to the modification of its electronic properties, and it also significantly improves the charge transfer ability and accelerates the reaction. Meanwhile, the unique hierarchical nanosheet arrays structure and abundant oxygen vacancies effectively adjust the number of OER active sites, which has a key role in developing a cost-effective oxygen electrode. Accordingly, V O -(Co, Fe) 3 O 4 /CC exhibits a relatively low overpotential of 286 mV at 10 mA cm −2 and a low Tafel slope of 41 mV dec −1 .