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.