Highly Defective Fe-Based Oxyhydroxides from Electrochemical Reconstruction for Efficient Oxygen Evolution Catalysis

Transition metal Fe-dominated materials generally show inefficient electrocatalytic oxygen evolution reaction (OER), while Fe-incorporated multimetallic compounds can exhibit high catalytic activity. In fact, there is always a controversy about the main active sites in Fe-involved OER elelctrocatalysts. Herein, we demonstrate a highly active mono-Fe-based OER electrocatalyst with a very low overpotential of 283 mV at a current density of 10 mA cm(-2) and a Tafel slope of 41.4 mV dec(-1). Systematic characterization reveals that the OER performance stems from Na dissolution during the electrocatalytic oxidation process, enabling the electrocatalyst reconstruction to form highly defective oxyhydroxides as highly active catalytic sites. Notably, the electrocatalytic activity can be significantly promoted through the introduction of a heterotransition metal. This work provides insights for active sites in OER catalysis, along with a facile route to tune the intrinsic activity.