Infrared spectroelectrochemical study of cyanide adsorption and reactions at platinum electrodes in aqueous perchlorate electrolyte

Abstract

In-situ IR spectroelectrochemistry was used to investigate the behavior of cyanide (CN-) at polycrystalline platinum surfaces in aqueous perchlorate (ClO4-) electrolyte. IR spectroelectrochemical data reveal the existence of a number of surface, as well as solution, cyanide species in the interfacial region. Within the double-layer potential region, there is IR evidence for several forms of adsorbed cyanide CNads- (νmax ≈ 2070 cm-1, ν′max ≈ 2145 cm-1, and ν″max ≈ 2170 cm-1). When the potential is made sufficiently positive, cyanide is oxidized to form cyanate (OCN-) (νmax = 2171 cm-1). Other solution cyanide species which may be formed at the platinum cyanide solution interface include hydrogen cyanide (HCN) (νmax ≈ 2095 cm-1) and the square-planar platinum cyanide complex Pt[CN]42-(νmax = 2133 cm-1) (IR-active Eu mode). The interfacial electrochemistry of the Pt | CN- + ClO4- system was found not only to be influenced by the applied electrode potential, but also to be driven by changes in the interfacial pH, which is potential-dependent. In-situ IR spectroelectrochemistry reveals details of the potential-dependent surface chemistry of the Pt / CN - system, the complexities of which cannot easily be studied by other techniques. © 1994.