High-frequency sonoelectrochemical processes: mass transport, thermal and surface effects induced by cavitation in a 500 kHz reactor

The use of high frequency ultrasound in electrochemical systems is of major interest for the optimisation of electrosynthetic and electroanalytical pr ocedures, especially when the strong mechanical effects of 20 kHz ultrasoun d are detrimental. The characterisation of a 500 kHz ultrasound reactor for sonoelectrochemical experiments by voltammetric and potentiometric measure ments revealed the presence of considerable thermal, as well as mass transp ort, effects depending on geometric parameters and the material used for th e construction of the working electrode. Micromixing and cavitation process es govern the mass transport to and from the electrode surface and are show n by atomic force microscopy (AFM) to cause erosion on the electrode surfac e. Electrochemically active films of Prussian blue are shown to be graduall y removed by cavitation erosion. Degassing the solution prior to sonication increases the efficiency of cavitation processes. (C) 1999 Elsevier Scienc e B.V. All rights reserved.