Anchoring single iridium atoms on defective nickel–iron layered double hydroxides for promoting oxygen evolution reaction

Nickel-iron layered double hydroxides (LDH) are recognized as the most active electrocatalysts for the alkaline oxygen evolution, but still suffer from their unsatisfied stability due to Fe dissolution and phase segregation. In this study, we demonstrate that anchoring iridium (Ir) single atoms over LDH with cationic defects can significantly increase both LDH stability and activity. The obtained catalyst exhibits the overpotential of 240 mV at a current density of 100 mA cm⁻² and 266 mV at 500 mA cm⁻², with the Tafel slope of 40.1 mV dec^-1. X-ray absorption spectroscopy results indicate that isolated single-atom iridium remains in the + 4 oxidation state, and anchoring Ir atoms into metal defective LDH is expected to strengthen Fe-O binding due to the weak covalency of Ir-O, which contributes to the promoting stability. This work not only develops a simple and practical strategy for the synthesis of Ir-NiFe^vac-LDH, but also provides a new idea for the development of OER catalytic materials with high activity and stability.