The effect of ultrasound on the electrochemical loading of hydrogen in palladium

Wark, Alastair and Crouch-Baker, S. and McKubre, M.C.H. and Tanzella, F.L. (1996) The effect of ultrasound on the electrochemical loading of hydrogen in palladium. Journal of Electroanalytical Chemistry, 418. pp. 199-204. ISSN 0022-0728

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Abstract

Although the application of ultrasound for the control and modulation of various chemical processes is a subject of continued interest [l], there is surprisingly little discus- sion in the recent literature of the effects of ultrasound on fundamental electrochemical processes. In early systematic studies of the hydrogen evolution reaction under acidic conditions [2,3], it was observed that, on a platinum elec- trode, the overvoltage for hydrogen evolution decreased by up to 30mV on the application of ultrasound, and that this decrease was largely independent of current density in the approximate range l-100 mA cm-‘, i.e. the Tafel slope was largely unaffected under these conditions. On removal of the ultrasound, the original polarization was regained only on continued electrolysis for up to 1 h. These results refer to electrolytes which had been pre-electrolysed for 10 to 20h. With more extensive pre-electrolysis (36h), the results were generally similar; however, the polarization decrease on the application of ultrasound was smaller (by a factor of two) under comparable conditions, and the origi- nal polarization was recovered rapidly on cessation of irradiation. On the application of ultrasound to a nickel electrode evolving hydrogen, the same general phe- nomenon was observed, i.e. a decrease in overvoltage without a significant change in Tafel slope [3]. For these experiments, the acoustic frequency was 3OOkHz and the ;icoustic intensity was estimated to be approximately I Wcmw2 of electrode area.