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Abstract: The underpotential deposition (UPD) of silver and lead on Au(111) was performed sequentially to produce a thin composite layer. Ag was deposited underpotentially in 1mM Ag2SO4 and 0.1M H2SO4 at 0.400V and 0.010V vs. Ag wire. The results of cyclic voltammetry carried out on this Ag/Au(111) electrode in a Pb2+ electrolyte with 0.1M HClO4 indicated contributions from both Au and Ag substrates. In situ STM images showed that the UPD of Pb on Ag/Au(111) had an unusual multilayer morphology. Cyclic Voltammetry was also used to demonstrate the stability and presence of the Ag adlayer in the Pb2+ electrolyte. In the presence of sodium nitrate, this composite system exhibits a catalytic effect on nitrate reduction that is not observed for Au(111), Ag/Au(111), Pb/Au(111), Ag(111), or Pb/Ag(111). Our results demonstrate that the Ag–Pb/Au(111) composite system has an enhanced catalytic effect on nitrate reduction. [Copyright &y& Elsevier]

Cyclic voltammetry and chronoamperometry have been employed for the preparation and characterization of noble metal electrode substrates modified with bismuth adlayers. The influence of bismuth ad-atoms on the electrocatalytic activity of the resulting platinum and gold modified electrode was investigated toward the electrooxidation of several sugar acid molecules in moderately alkaline medium. A direct comparative study regarding the catalytic activity between platinum and gold electrodes has been carried out in order to obtain useful information on the electrooxidation mechanism of sugar acids. It is found that different pre-adsorption processes of analyte on the platinum and gold electrodes were involved giving rise to different adsorption states in the oxide region and double region of potentials, respectively. The bismuth adsorbed species acts as a true catalyst on the direct electrooxidation pathway, providing the oxygen necessary for the oxidation of organic molecules adsorbed on the PtOx or Au sites in the oxide and double region, respectively. [Copyright &y& Elsevier]