EFFECT OF SURFACE-ROUGHNESS ON DIFFUSION-LIMITED CHARGE-TRANSFER

A theory is developed for diffusion-limited charge transfer on a non-f ractally rough electrode. The perturbation expressions are obtained fo r concentration, current density and measured diffusion-limited curren t for arbitrary one- and two-dimensional surface profiles. The random surface model is employed for a rough electrode\electrolyte interface. In this model the gross geometrical property of an electrochemically active rough surface - the surface structure factor-is related to the average electrode current, current density and concentration. Under sh ort and long time regimes, various morphological features of the rough electrodes, i.e. excess area (related to roughness slope), curvature, correlation length, etc. are related to the (average) current transie nts. A two-point Pade approximant is used to develop an all time avera ge current expression in terms of partial morphological features of th e rough surface. The inverse problem of predicting the surface structu re factor from the observed transients is also described. Finally, the effect of surface roughness is studied for specific surface statistic s, namely a Gaussian correlation function. It is shown how the surface roughness enhances the overall diffusion-limited charge transfer curr ent.