Voltammetric and amperometric analyses of electrochemical nucleation: electrodeposition of copper on nickel and tantalum

We present theoretical and experimental results demonstrating how the techniques of cyclic voltammetry (CV) and potential step (PS) amperometry can be combined for quantitative analysis of electrochemical nucleation reactions. We have integrated two existing technique-specific (PS or CV) theoretical models of 3-D nucleation in a single framework of the general nucleation rate law. This framework provides a phenomenological basis for combining CV and PS for nucleation studies. We report two experimental systems, involving electrodeposition of Cu2+ on Ni and Ta, that exhibit nucleation behaviors predicted from these theoretical considerations. Deposition and stripping of Cu2+ are found to be reversible at the Ni surface, and irreversible at the (naturally oxidized) Ta surface. For both the Ni/Cu2+ and Ta/Cu2+ systems, distinct features of 3-D nucleation are detected in CV. These features are investigated further through detailed examination of PS-induced current transients. The common links between the nucleation currents observed in the CV and PS experiments are discussed in detail.