On reverse 2D nucleation—growth—collision in the electroreduction of incomplete HgS bilayers at the mercury/electrolyte interface

Abstract

The dissolution of incomplete HgS bilayers has been investigated by means of current-time ( i-t) transients using the potential step technique. The transients can be theoretically well described by a model which involves a three-stage process. The first stage corresponds to an electrodesorption of those regions of the first monolayer which are not covered by the islands of the second layer. Here, the HgS monolayer consists of a condensed and an expanded phase and only the expanded phase can be electrodesorbed. The dissolution of the condensed phase clusters at their edges is much faster than the electrodesorption of the expanded phase. The electrodesorption of the first monolayer proceeds up to the time when all monolayer clusters are dissolved. Then as the second stage of the overall process, the dissolution of the remaining bilayer islands starts according to a reverse two-dimensional instantaneous nucleation—growth—collision, i.e. a dissolution of the bilayer islands at their edges. The third stage of the HgS bilayer dissolution begins when all bilayer islands are dissolved and can be theoretically well described with a first-order electrodesorption process of the admolecules of the first monolayer.