Studies of the Ag-Pt Interface Formed by Ag Deposition from Sulfolane Solutions on Thin Film Electrodes

Vapor deposition, thin film fabrication techniques have been applied to the preparation of Pt electrodes of various topographies. Large variations were observed in the electrical resistivities of these electrodes as a function of porosities. The effect of these film preparation techniques on Ag electrodeposition from solutions of AgClO4 in sulfolane was examined. Roughness factors, obtained from differential capacitance measurements, varied from 1.0 to 32.8 over the range from bulk Pt to the most porous films. Analysis of cyclic voltammetric data and double potential step chronocoulometric results indicate silver deposition occurs without underpotential deposition in sulfolane in contrast to behavior found in aqueous medium. Little difference is noted in the diffusion-controlled Ag deposition currents as a function of active electrode surface area except at the shortest electrolysis times, msec. Auger electron spectroscopy and argon ion sputter etching were used to examine the surface and depth profile of controlled potential-deposited thin layers of Ag. Porous films showed deep penetration of all monitored species (Ag, Pt, S, Cl). Detectable amounts of solvent and Ag are found throughout the film electrode. The degree of penetration decreases rapidly with increasing film density. The surface analysis results have been correlated to the electrochemical behavior and interpreted in terms of the extent of solvent, solute interaction prior to electrodeposition.