Detection of the fractal character of compact adsorbed layers by the dropping mercury electrode

Abstract

The development of compact adsorbed layers at the dropping mercury electrode is used for the detection of resulting changes in the geometry of the electrode–solution interface from Euclidean to fractal. A simple size scaling method of the Hg drop surface is applied, which focus on the time dependence of the drop area under conditions of constant adsorbate and base electrolyte concentration, constant potential and constant mercury flow rate. It is found that the slope of the log–log plots of capacitance or capacitance current against electrode surface area or electrode radius is increasing upon the formation of a compact adsorbed layer. Under equilibrium conditions the slope values of the linear log–log plots can be reasonably identified with the fractal dimension of the electrode/solution interface. However, due to the limited extent of the power-law range of the feature vs. scale relation, the size scaling method of the dropping mercury electrode can be used to probe fractal adsorbate films on a strictly qualitative level.