Atomic transport processes on electrodes in liquid environment

We present an overview on the method of analysing equilibrium step fluctuations on metal electrodes to study atomic transport processes at the solid/liquid interface. It is demonstrated that this method provides an access road to a quantitative understanding of surface mobility on metal electrodes. Likewise it is shown that the investigation of step fluctuations is a method to determine activation energies and - with the help of recently introduced temperature dependence experiments - pre-exponential factors. We will show that the dependence of surface mobility on electrode potential and on the electrolyte may be rather complex. As examples, we present STM studies on stepped Cu(111) and Ag(111) electrodes in aqueous electrolytes. For Cu(111) in 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 CuSO₄ and H₂SO₄, an L^1/2t^1/2-dependence (with L the step distance) near the potential of fast Ag dissolution is observed. This time dependence corresponds to an atomic transport based on terrace diffusion and transport through the liquid. We also show that the results of temperature dependent studies of step fluctuations on Ag(111) are in excellent agreement with previous investigations concerning the potential dependence.