Coordination of silver(I) at the surface of carbon paste electrodes modified with 2,5,8-trithia[9]-m-cyclophane as studied by cyclic voltammetry

Abstract

The electrochemical behaviour of silver(I) at carbon paste electrodes (CPE) modified by 2,5,8-trithia[9]- m -cyclophane (TTCP) were studied voltammetrically in aqueous solutions of sodium perchlorate. Up to three cathodic peaks and anodic currents were observed in the cyclic voltammograms at the modified CPE, in contrast to the voltammograms of Ag + at the unmodified CPE in the presence and in the absence of TTCP in the solution. In the voltammograms high cathodic currents are contrasted by low anodic currents, e.g. in the case of 1×10 −5 M or 2×10 −5 M Ag + cathodic currents in are the range from 10 to 30 μA, whereas anodic currents are lower than 2 μA. The electrode reactions of silver at the modified electrode are discussed. The peak potential and peak currents of the cathodic currents depend strongly on the preceding cycle. The appearance of two cathodic peaks is attributed to oxidative formation of surface complexes of Ag(I) at positive potentials after preceding cathodisation with deposition of Ag(0). The reduction potential and consequently the stability of the complexes formed depended on the upper reversal potential. Furthermore, the influence of potentiostatic pretreatment and pretreatment at open circuit is studied. After pretreatment at open circuit a cathodic peak with time-dependent peak current appeared in the second scan to negative potentials.