Electrochemical adsorption of cyanide on Ag(111) in the presence of cetylpyridinium chloride

The behaviour of an Ag(111) electrode in contact with a neutral perchlorate solution containing cetylpyridinium chloride (CPC) and potassium cyanide was studied as a function of potential. The understanding of the interaction of organic additives relevant to metal plating processes with specific crystal faces can provide guidelines for the design of advanced and environmentally friendly electrodeposition processes. CPC acts as a cathodic depolariser and an efficient hydrogen scavenger in precious metal and alloy electrodeposition baths containing cyanocomplexes. In situ spectroelectrochemical FT-IR measurements were carried out using both p- and s-polarised radiation. FT-IR data were complemented by SERS measurements on electrochemically roughened polycrystalline Ag in order to clarify the potential-dependent orientational behaviour of CPC. Cyclic voltammetry and differential capacitance measurements were employed to asses the electroactivity and adsorption ability of the relevant species. The results obtained evidenced a reorientation of the heteroaromatic ring from flat to vertical on shifting the electrode potential from anodic to cathodic. Surface CN- stretching bands were observed with and without CPC in the solution. As a function of potential, the presence of CPC shifts the CN- peak position to higher wavenumbers, suggesting the existence of an interaction between adsorbates, and increases in the peak intensities, possibly denoting coadsorption on interacting adsorption sites. (C) 2004 Elsevier B.V. All rights reserved.