The hanging meniscus contact: geometry induced diffusional overpotential. The reduction of oxygen in dimethylsulphoxide at Au(111)

Mass transport in the hanging meniscus configuration has been studied. The effects of this geometry on an electrochemical reaction of a gas phase spec ies with a high solubility in the electrolyte phase have been investigated, both numerically and experimentally. The steady-state process is modelled in cylindrical polar coordinates using a fully implicit finite-difference n umerical method and solved with a preconditioned Krylov subspace method, Th e numerical method incorporates an expanding mesh technique to optimise ele ctrode flux error-cancelling. The nature of the meniscus boundary such as t o permit the ingress of electroactive material mentioned, but not the egres s of electrode reaction products is shown to result in a diffusional overpo tential in the steady-state voltammogram. This observation has been examine d experimentally by using the reduction of O-2 in dimethylsulphoxide soluti on on a Au(lll) single crystal electrode. (C) 2001 Elsevier Science B.V. Al l rights reserved.