Electrochemical reactions in adsorption of organosulfur molecules on gold and silver: Potential dependent adsorption

The early stage of adsorption of organosulfur molecules on gold and silver was investigated by electrochemical and quartz crystal microgravimetric met hods. The potential shifts of the substrate metals, current flowing through the substrates, and the surface mass increase observed during the adsorpti on process were found to support newly proposed electrochemical mechanisms of chemisorption steps: Thiols adsorb on Au and Ag by an anodic oxidation, whereas dialkyl disulfides adsorb through a reaction that results in net ca thodic current. The relative rates of the adsorption depended on the potent ial of the substrate in accordance with the electrochemical mechanisms. The increase in surface mass due to adsorption was observed to closely paralle l the charge expended in the electrochemical reactions.