In Situ Growth of Amorphous NiFe Hydroxides on Spinel NiFe2O4 via Ultrasonic-Assisted Reduction for an Enhanced Oxygen Evolution Reaction

Amorphous Ni–Fe hydroxides (NiFe(OH)x) are considered to possess promising potential as oxygen evolution reaction (OER) electrocatalysts, but amorphous NiFe(OH)x is hard to synthesize due to the complicated multistep synthesis process. Herein, amorphous NiFe(OH)x is successfully grown in situ on the surface of NiFe2O4 via an ultrasonic-assisted reduction method. This method takes advantage of ultrasonic cavitation to achieve a unique reduction effect, migration of Ni and Fe cations of NiFe2O4 to the crystal surface, and in situ growth of amorphous NiFe(OH)x, thereby forming a NiFe2O4/NiFe(OH)x composite. This material exhibits enhanced electrochemical performance with an overpotential of 276 mV at 10 mA cm–2. The ultrasonic-assisted reduction method can be used to synthesize amorphous NiFe(OH)x with no residual reactants, providing a simple and facile way to synthesize amorphous hydroxide materials.