Model Hierarchy to Reanalyze Results from an Archetypical Experiment on the Kinetics of Heterogeneous Nucleation – the Electrodeposition of Hg on Pt, by I. Markov and E. Stoycheva

We employ hierarchy of models (HoM) with 2, 3 and 4 parameters to reanalyze the nucleation kinetics in the electrodeposition as quantified by n(t) - “the number of nuclei vs. time” data obtained at different overvoltages from precise experiments on electrodeposition of Hg on two different types of Pt-cathodes by Ivan V. Markov and Evgenia Stoycheva [1]. The obtained two scales, nmax and , are used to rescale the original data mapping it on a master curve in coordinates . Our main result is obtained by studying further the dependence of these two scales on the overvoltage (analogue of supersaturation). Surprisingly, for one of the two cathode types - the “hemispherical single-crystal electrode” (as defined by the authors), there is discontinuity in the “ vs. overvoltage” dependence – an almost horizontal jump from 85 to 86 mV accompanied by a change in the slope of the dependence - it is ~ -1 and ~ -0.5 after. For the other cathode - “plane structureless platinum electrode”,  decreases smoothly. Combined, these two behaviors point at the so called “cusp catastrophe”. We compare our findings with published results on protein nucleation.