Construction of Self-healing Active Centers over Amorphous Ni<sub>2</sub>Fe(OH)<sub><i>x</i></sub> Nanosheets for Enhanced Oxygen Evolution Performance.

Abstract

Developing efficient nickel-iron-based electrocatalysts for the oxygen evolution reaction (OER) still remains a challenge for long-term application in water electrolysis. Herein, amorphous Ni₂Fe hydroxide nanosheets with self-healing active centers supported on stainless steel mesh (<i>a</i>-Ni₂Fe(OH)_<i>x</i>/SSM) are fabricated using a simple electrochemical deposition strategy. <i>In situ</i> Raman evidence shows that the amorphous structure of <i>a</i>-Ni₂Fe(OH)_<i>x</i>/SSM exhibits strong self-healing ability, efficiently promoting the rapid interconversion between the γ-NiOOH intermediate and Ni-based hydroxides during electrocatalysis. As a result, the as-obtained <i>a</i>-Ni₂Fe(OH)_<i>x</i>/SSM exhibits a low overpotential of 247 mV at 100 mA cm^-2 and robust electrochemical stability for 200 h. Moreover, an anion-exchange membrane electrolyzer for water splitting is assembled utilizing <i>a</i>-Ni₂Fe(OH)_<i>x</i>/SSM as the anode, and current densities of 500 and 1000 mA cm^-2 are achieved at 1.62 and 1.72 V, respectively, with stable performance at 500 mA cm^-2 over 30 h. This work provides a facile approach for designing amorphous catalysts for various useful reactions.