Please choose your delivery country and your customer group
The impedance of a rotating disk is calculated under conditions where the time average current to the disk is below the limiting current. The reaction at the surface of the disk is of the redox type; consequently the influence of product concentrations on the disk impedance has to be included in the calculations. The double-layer theory is used to calculate the surface excesses of all ionic species present in the solution with the assumption that there is no specific adsorption. It is shown that under these circumstances the concentration fluctuations of both cation and anion of the supporting electrolyte caused by migration are of the same order of magnitude as the concentration fluctuations of reactant and product. Therefore, the usual treatment of electrochemical impedance problems, neglecting the influence of the supporting electrolyte, is not a priori valid. The last part of the thesis describes the application of the limiting-current technique to mass-transfer studies of packed beds at very low Peclet numbers. The results show that the correlations usually used for these regions start to break down when the Peclet number is below 20.