Random nucleation and growth of Pt nanoparticles at the polarised interface between two immiscible electrolyte solutions

Cyclic voltammetry and potential-step chronoamperometry are used to study the Pt deposition at the polarised water vertical bar 1,2-dichloro-ethane (DCE) interface through reduction of a Pt(II) chloro-complex in water by 1,1'-dimethylferrocene in DCE. Thermodynamic analysis suggests that the deposition is controlled by the interfacial kinetics, and that the activity of the metal particle at ITIES does not differ much from that of the bulk metal phase. It is shown that the shape of the experimental potential-step current transients could be described with the help of the available theory of nucleation and growth of a metal particle at a liquid-liquid interface. However, the repeated potential-step experiments on the bare interface reveal that the initial rate of the Pt deposition can attain a broad range of values that spans over two orders of magnitude. It is proposed that this surprising feature is related to the random rate of the formation of nuclei with a critical size that is necessary for a stable growth to occur. Explanation is supported by computer simulation for a model assuming that the interfacial metal particle can either grow or decline by one atom, or remain inactive with a comparable probability. (c) 2005 Elsevier B.V. All rights reserved.