Diffusion‐Controlled Multisweep Cyclic Voltammetry: III . Deposition of Silver on Stationary and Rotating‐Disk Electrodes

An experimental study of diffusion‐controlled silver electrodeposition has been carried out in order to investigate the applicability of the model for reversible metal deposition during multisweep cyclic voltammetry. For a stationary planar electrode, excellent agreement between theory and experiment has been obtained for the position of the cathodic current maxima on the potential axis, as well as for the dependence of their magnitude on parameters such as sweep rate, cathodic reversal potential, and number of applied sweeps. Anodic currents measured at the foot of the wave deviated from theoretical predictions as a consequence of the small but uncompensated resistance of the electrolyte. In an effort to predict and therefore control the amount of deposit integral charges associated with each sweep have been measured and successfully correlated with the parameters of the experiment. It has been found that at millimolar concentrations, deposit thicknesses of the order of up to 20 monolayers can be formed with quantitative control. Experiments with a rotating‐disk electrode have demonstrated that a periodic current response is obtained upon multiple sweeping, as predicted by theory. First sweep and periodic currents normalized with respect to the limiting current could be correlated with the dimensionless sweep rate in accordance with the theoretical predictions. Contrary to previous investigations, the diffusion coefficient of the silver ion was determined by limiting current measurements, and the value thus obtained was subsequently used to successfully correlate stationary electrode cyclic voltammetry data. During limiting current measurements with very slow sweeps, the development of surface roughness was observed as a significant increase of the current from the constant value obtained at faster sweeps. Based on the dimensionless sweep rate, a semiempirical criterion was developed for the optimal conditions for the potentiodynamic determination of steady‐state limiting currents, the use of which may eliminate errors arising from both transient effects and surface area increase due to roughness.