Fundamental Studies of Surfaces Processes and Trace Analysis Using Solid Electrodes.

Abstract

Abstract : Physical electrochemical and electroanalytical studies were undertaken at silver, gold, and platinum electrodes. Underpotential deposition (UPD) studies were undertaken at polycrystalline silver electrodes. Using the electrochemical quartz crystal microbalance, it was shown that Pb(II) species are adsorbed at silver when the Pb(II) exists as an anion in solution. The anionic Pb(II) adsorbate is ultimately reduced to a underpotential Pb(0) with concomitant anion (ligand) expulsion from the electrode surface. Adsorption of sulfide ion (UPD without faradaic charge transfer) also occurs at silver from alkaline sulfide solutions. Three distinct UPD states were identified. The coulostatic formation of UPD Hg(0) at a gold electrode was studied in sulfuric acid using the EQCM. It was found that a monolayer of Hg(0) is formed along with an overlayer of mercury (I) bisulfate. The formation of silver sulfide during the electrooxidation of thioacetamide was established. A theoretical analysis of cathodic stripping peaks based on a hemispherical model with progressive nucleation was performed. The results were used in interpreting inductions times associated with the formation of cathodic stripping peaks at silver electrodes. The uncompensated ohmic potential drop at microelectrodes under steady state diffusion conditions was shown to be susceptible to a theoretical analysis. A method for determining the current efficiency for the electropolymerization process was developed and confirmed using azulene. (aw)