Electrochemical behavior of silver single-crystal electrodes in 1 M NaNO3 solution in the absence and in the presence of decanethiol films

Abstract

The surface properties of silver single-crystal faces (111) and (210) in 1 M NaNO3 aqueous solution in the absence and in the presence of monolayer n-decanethiol (DT) films are studied by the methods of cyclic voltammetry and electrochemical impedance using the meniscus contact technique. It is experimentally shown that, in the potential range from 0 to −0.5 V, the faradaic processes are absent and low currents are recorded on the unmodified silver surfaces. It is shown that the DT molecules, which are adsorbed on the nonoxidized surfaces of silver faces, spontaneously form (during 72 h) compact structurized films. The films are stable in the air and in the electrolyte solutions and totally block the surfaces of both faces. The impedance spectra, which were measured for each interface in a wide range of frequencies, are analyzed and interpreted. The measurements were performed by the use of the corresponding empirical equivalent circuits containing perfect and imperfect analogs of electrical circuits; complex nonlinear least squares (CNLS) regression method was applied for the calculations. The capacitance, ohmic resistance, and adsorbed monolayer thickness were estimated.