A Simple Synthetic Strategy toward Defect-Rich Porous Monolayer NiFe-Layered Double Hydroxide Nanosheets for Efficient Electrocatalytic Water Oxidation

In this work, porous monolayer nickel-iron layered double hydroxide (PM-LDH) nanosheets with a lateral size of approximate to 30 nm and a thickness of approximate to 0.8 nm are successfully synthesized by a facile one-step strategy. Briefly, an aqueous solution containing Ni2+ and Fe3+ is added dropwise to an aqueous formamide solution at 80 degrees C and pH 10, with the PM-LDH product formed within only 10 min. This fast synthetic strategy introduces an abundance of pores in the monolayer NiFe-LDH nanosheets, resulting in PM-LDH containing high concentration of oxygen and cation vacancies, as is confirmed by extended X-ray absorption fine structure and electron spin resonance measurements. The oxygen and cation vacancies in PM-LDH act synergistically to increase the electropositivity of the LDH nanosheets, while also enhancing H2O adsorption and bonding strength of the OH* intermediate formed during water electrooxidation, endowing PM-LDH with outstanding performance for the oxygen evolution reaction (OER). PM-LDH offers a very low overpotential (230 mV) for OER at a current density of 10 mA cm(-2), with a Tafel slope of only 47 mV dec(-1), representing one of the best OER performance yet reported for a NiFe-LDH system. The results encourage the wider utilization of porous monolayer LDH nanosheets in electrocatalysis, catalysis, and solar cells.