Nucleation and growth of mercury on Pt nanoelectrodes at different overpotentialsElectronic supplementary information (ESI) available: Additional Hg deposition transients. See DOI: 10.1039/c3sc52488d

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. Sharp transition from single nucleus formation at a nanoelectrode to multiple nucleation occurs within a narrow range of overpotentials.