Mechanistic Study of Sn Electrodeposition on TiO2 Nanotube Layers: Thermodynamics, Kinetics, Nucleation, and Growth Modes

The electrodeposition of Sn nanowires from citrate buffered baths on titania nanotubes is investigated. Electrochemical studies are combined with scanning electron microscopy (SEM) observations to get an insight into nucleation and growth modes. The electrochemical potential of Sn citrate complexes, exchange current density ((4 ± 1) 10 −7 A/cm 2 ), and the diffusion coefficient of Sn citrate complex in solution ((8 ± 1) 10 −6 cm 2 /s) are determined. The high transfer coefficient (α = 0.8 ± 0.1) of the Sn reduction indicates a highly asymmetrical reaction, which is most likely coupled with a physical adsorption−desorption process on the surface of the growing Sn crystallite. Nucleation and growth appears to be instantaneous according to the model developed by Scharifker and Hills.