Silver electrodeposition from water-acetonitrile mixed solvents and mixed electrolytes in the presence of tetrabutylammonium perchlorate. Part I-electrochemical nucleation on glassy carbon electrode

Nucleation and growth of silver, electrodeposited from water-acetonitrile (CH3CN from 0 to 100% by volume) mixed solvents on glassy carbon electrodes, was studied by means of double-sweep voltammetry, current-time transients (CTT) and scanning electron microscopy (SEM). The effects of the addition of the specifically interacting tetrabuthylammonium cation were also investigated. From voltammetries, the formal potential, the nucleation potential and the cathodic current efficiency have been evaluated as a function of the mixed solvent composition. The key role on nucleation kinetics of transferring Ag+ from the bulk phase to the CH3CN-enriched electrode/solution interphase has been highlighted. CTT transients were described by a model combining instantaneous and progressive nucleation mechanisms. SEM images highlighted the effects of the presence of the organic solvent, which yields to a more regular growth, and of the quaternary ammonium salt, which exhibits grain-refining properties.