INFRARED SPECTROELECTROCHEMICAL STUDY OF CYANIDE ADSORPTION AND REACTIONS AT PLATINUM-ELECTRODES IN AQUEOUS PERCHLORATE ELECTROLYTE

In-situ IR spectroelectrochemistry was used to investigate the behavio r of cyanide (CN-) at polycrystalline platinum surfaces in aqueous per chlorate (ClO4-) electrolyte, IR spectroelectrochemical data reveal th e existence of a number of surface, as well as solution, cyanide speci es in the interfacial region. Within the double-layer potential region , there is IR evidence for several forms of adsorbed cyanide CN(ads)- (nu(max) almost-equal-to 2070 cm-1, nu(max)''' almoat-equal-to 2145 cm -1, and nu(max) almost-equal-to 2170 cm-1). When the potential is made sufficiently positive, cyanide is oxidized to form cyanate (OCN-) (nu (max) = 2171 cm 1). Other solution cyanide species which may be formed at the platinum/cyanide solution interface include hydrogen cyanide ( HCN) (nu(max) = 2095 cm-1) and the square-planar platinum cyanide comp lex Pt[CN]42- (nu(max) = 2133 cm-1) (IR-active E(u) mode). The interfa cial electrochemistry of the Pt\CN- + ClO4-system was found not only t o be influenced by the applied electrode potential, but also to be dri ven by changes in the interfacial pH, which is potential-dependent. In -situ IR spectroelectrochemistry reveals details of the potential-depe ndent surface chemistry of the Pt\CN- system, the complexities of whic h cannot easily be studied by other techniques.