General time-dependent mass balance equation

Mass balance equations at the electrode surface, for the case of time-depen dent geometry of the depletion layer, that are valid for any stoichiometry and any value of diffusion coefficients, are formulated and evaluated. Anal ysis of the errors identifies a simple, general mass balance equation. Erro rs due to application of the general mass balance equation for mixed diffus ion within the entre depletion layer are determined also. The focus is on m ixed planar and spherical diffusion. (C) 2001 Elsevier Science B.V. All rig hts reserved.