The early stage of adsorption of organosulfur molecules on gold and silver was investigated by electrochemical and quartz crystal microgravimetric methods. The potential shifts of the substrate metals, current flowing through the substrates, and the surface mass increase observed during the adsorption 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 cathodic current. The relative rates of the adsorption depended on the potential of the substrate in accordance with the electrochemical mechanisms. The increase in surface mass due to adsorption was observed to closely parallel the charge expended in the electrochemical reactions.
Electrodes made by depositing ruthenium oxide on conducting poly͑3,4-ethylenedioxythiophene͒ ͑PEDT͒ were studied for their electrochemical and impedance properties. In acidic electrolytes the PEDT-RuO x composite electrodes exhibited large capacitance due to contributions from the double-layer capacitance and the faradaic capacitance. Optimization of the thickness of the conducting polymer film and the amount of ruthenium deposition was found necessary to realize large specific capacitance. The specific capacitance based on the combined mass of PEDT-RuO x was 420 F/g, and the specific capacitance based on the mass of RuO 2 was 930 F/g. The energy storage density of a capacitance cell constructed with a pair of PEDT-RuO x electrodes reached 27.5 Wh/kg when the cell was charged to 1.0 V. The impedance analysis of the composite electrode revealed that both the double-layer capacitance and the pseudocapacitance originating from both PEDT and RuO x contribute to large specific capacitance.
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