Atomic transport processes on electrodes in liquid environment

We present an overview on the method of analysing equilibrium step fluctuat ions on metal electrodes to study atomic transport processes at the solid/l iquid interface. It is demonstrated that this method provides an access roa d to a quantitative understanding of surface mobility on metal electrodes. Likewise it is shown that the investigation of step fluctuations is a metho d to determine activation energies and-with the help of recently introduced temperature dependence experiments-pre-exponential factors. We will show t hat the dependence of surface mobility on electrode potential and on the el ectrolyte may be rather complex. As examples, we present STM studies on ste pped Cu(111) and Ag(111) electrodes in aqueous electrolytes. For Cu (111) i n HCl, we find that the time dependence of step fluctuations obeys a t(1/3) -law, which entails that step fluctuations are dominated by fast attachment /detachment kinetics at steps and slow terrace diffusion. For Ag(111) in Cu SO4 and H2SO4, an L(1/2)t(1/2)- dependence (with L the step distance) near the potential of fast Ag dissolution is observed. This time dependence corr esponds to an atomic transport based on terrace diffusion and transport thr ough the liquid. We also show that the results of temperature dependent stu dies of step fluctuations on Ag(111) are in excellent agreement with previo us investigations concerning the potential dependence.