Electrochemical kinetics and growth modes of silver deposits on polyfaceted platinum spherical electrodes

Abstract

The Ag electrodeposition on Pt spherical substrates was investigated over a wide range of experimental conditions to establish a correlation between the kinetics of the process and the different growth modes of the Ag overlayer. At E_d ≊ E_rev, the electrodeposition of the first Ag layer obeys a combined adsorption-desorption and nucleation and 2-D growth process under diffusion control. At E_d ≊ E_rev, the formation of the 2-D Ag layer proceeds through an adsorption mechanism, whereas the formation of the 3-D Ag layer fits a progressive nucleation and 3-D growth mechanism under diffusion control. Finally, when E_d < E_rev, a potential threshold related to Ag dendritic growth, the kinetics of the reaction apparently obeys a progressive nucleation and 1-D growth. This process is triggered at edges and corners of large Ag crystals. Dendritic growth takes place outside the diffusion layer defined around the Pt substrate sphere. In this case migration plays a substantial role in the process.