Nucleation and growth of mercury on Pt nanoelectrodes at different overpotentials

Three-dimensional nucleation and growth on active surface sites are fundamentally important initial stages of electrodeposition of metals. Electrodeposition of Hg is a widely employed model for studies of such processes because the near-ideal hemispherical growth of its liquid nuclei can be used to check the existing theory. In this article we discuss nucleation/growth of Hg at 50–100 nm radius Pt electrodes. Recently, atomic force microscopy (AFM) was used to demonstrate that a nanoelectrode of this size has a single active site for Ag nucleation, at which the growth of a single nucleus was monitored (Chem. Sci., 2012, 3, 3307). Here we report similar observations for Hg nucleation/growth at relatively low overpotentials (e.g., 25 to 75 mV). However, at higher overpotentials (e.g., ≥100 mV), the kinetics of this process changed, and very fast multiple nucleation of Hg was observed. Possible origins of this phenomenon are discussed.