In this investigation, we report on the development of
a method
for activating polycrystalline metallic nickel (Ni(poly)) surfaces
toward the hydrogen evolution reaction (HER) in N2-saturated
1.0 M KOH aqueous electrolyte through continuous and pulsed ultrasonication
(24 kHz, 44 ± 1.40 W, 60% acoustic amplitude, ultrasonic horn).
It is found that ultrasonically activated Ni shows an improved HER
activity with a much lower overpotential of −275 mV vs RHE
at −10.0 mA cm–2when compared to nonultrasonically
activated Ni. It was observed that the ultrasonic pretreatment is
a time-dependent process that gradually changes the oxidation state
of Ni and longer ultrasonication times result in higher HER activity
as compared to untreated Ni. This study highlights a straightforward
strategy for activating nickel-based materials by ultrasonic treatment
for the electrochemical water splitting reaction.