Sonoactivated polycrystalline Ni electrodes for alkaline oxygen evolution reaction

The development of cost-effective and active water-splitting electrocatalysts is an essential step toward the realization of sustainable energy. Its success requires an intensive improvement in the kinetics of the anodic half-reaction of the oxygen evolution reaction (OER), which determines the overall system efficiency to a large extent. In this work, we designed a facile and one-route strategy to activate the surface of metallic nickel (Ni) for the OER in alkaline media by ultrasound (24 kHz, 44 W, 60% acoustic amplitude, ultrasonic horn). Sonoactivated Ni showed enhanced OER activity with a much lower potential at + 10 mA cm−2 of + 1.594 V vs. RHE after 30 min ultrasonic treatment compared to + 1.617 V vs. RHE before ultrasonication. In addition, lower charge transfer resistance of 11.1 Ω was observed for sonoactivated Ni as compared to 98.5 Ω for non-sonoactivated Ni. In our conditions, ultrasound did not greatly affect the electrochemical surface area (Aecsa) and Tafel slopes however, the enhancement of OER activity can be due to the formation of free OH• radicals resulting from cavitation bubbles collapsing at the electrode/electrolyte interface.