Rhodium electrodeposition on pyrolytic graphite electrode: Analysis of chronoamperometric curves

The electrodeposition of metallic rhodium on pyrolytic graphite from 10 mM Na3RhCl6 +0.5 M NaCl aqueous solution was investigated for the first time. From the analysis of chronoamperometric curves, the nucleation kinetics was compared for two-dimensional (2D) and three-dimensional (3D) electrodeposition processes, applying various models. Rh electrodeposition at −172 and −232 mV vs. Ag/AgCl was interpreted in terms of 3D process of progressive type which turns into instantaneous one at more negative potentials. The principal nucleation parameters (nucleation rate constant, nucleation density) are calculated by using two frequently used models for 3D nucleation and growth (Scharifker–Mostany and Mirkin–Nilov–Heerman–Tarallo), using different fitting procedures. It is shown that both models give similar results.