Understanding the Effects of Ultrasound (408 kHz) on the Hydrogen Evolution Reaction (HER) and the Oxygen Evolution Reaction (OER) on Raney-Ni in Alkaline Media

• Published in: Ultrasonics sonochemistry 2022-03, Vol.84, p.105979-105979, Article 105979
• Main Authors: Foroughi, Faranak, Immanuel Bernäcker, Christian, Röntzsch, Lars, Pollet, Bruno G.
• Format: Article
• Language: English
• Subjects: Alkaline; Hydrogen evolution reaction (HER); Oxygen evolution reaction (OER); Raney-Nickel; Short Communication; Sonoelectrochemistry; Ultrasound
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2022.105979

•Under silent conditions, the HER and OER activities of Raney-Ni in weak alkaline media improve when the electrolyte temperature is increased.•The HER activity of Raney-Ni in weak alkaline media under ultrasonic conditions (408 kHz) increases at 25 °C while the OER activity of Raney-Ni under ultrasonic conditions is not affected.•Combining ultrasonication (408 kHz) at high electrolyte temperatures do not improve the HER and OER activities of Raney-Ni in weak alkaline media.•Ultrasound (408 kHz) has no influence on the stability of the Raney-Ni coating. The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) occurring at the Raney-Ni mesh electrode in 30 wt.-% aqueous KOH solution were studied in the absence (silent) and presence of ultrasound (408 kHz, ∼54 W, 100% acoustic amplitude) at different electrolyte temperatures (T = 25, 40 and 60 °C). Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) experiments were performed to analyse the electrochemical behaviour of the Raney-Ni electrode under these conditions. Under silent conditions, it was found that the electrocatalytic activity of Raney-Ni towards the HER and the OER depends upon the electrolyte temperature, and higher current densities at lower overpotentials were achieved at elevated temperatures. It was also observed that the HER activity of Raney-Ni under ultrasonic conditions increased at low temperatures (e.g., 25 °C) while the ultrasonic effect on the OER was found to be insignificant. In addition, it was observed that the ultrasonic effect on both the HER and OER decreases by elevating the temperature. In our conditions, it is suggested that ultrasound enhances the electrocatalytic performance of Raney-Ni towards the HER due to principally the efficient gas bubble removal from the electrode surface and the dispersion of gas bubbles into the electrolyte, and this effect depends upon the behaviour of the hydrogen and oxygen gas bubbles in alkaline media.