Application of ultrasound in electrochemistry. An overview of mechanisms and design of experimental arrangement

An overview of possible mechanisms by which sonication can influence electrochemical processes is given. Four mechanisms are discussed: - acoustic streaming; - microstreaming and turbulence due to cavitation; - formation of microjets in the course of collapse of cavitation bubble; - shock waves; and possible effects are illustrated on several examples. The most effective process is formation of microjets, which can not only decrease diffusion layer thickness under 1 mu m, but also activate (depassivate) electrode surface. Design of experimental arrangement with maximum participation of microjets is proposed. Two approaches are proposed: - focusing of ultrasound on the working electrode and reduction of energy losses by over-pressure; -tuning the reactor to obtain resonance, i.e. formation of stationary waves by activating reactor in its resonant mode. (C) 2010 Elsevier B. V. All rights reserved.