VOLTAMMETRIC AND SPECTROSCOPIC CHARACTERIZATION OF CYANIDE ADLAYERS ON PT(H,K,L) IN AN ACIDIC

Irreversibly adsorbed cyanide adlayers formed on single-crystal platin um electrodes were studied by cyclic voltammetry and in-situ FTIR spec troscopy in a perchloric medium. A vibrational band around 2100 cm(-1) was assigned to the C-N stretching vibration of adsorbed cyanide on t he three electrode surfaces. Cyanide adlayers seem to be stable on Pt( lll) in a wide range of potentials. Tuning rates of 100 and 30 cm(-1) V-1 were measured for the band at 2100 cm(-1) below and above 0.5 V, r espectively. Adsorbed cyanide has a complex behavior on Pt(100). The p olarization of the cyanide-covered Pt(100) electrode in the potential region below 0.4 V (RHE) leads to the formation of a CO adlayer (band at 1820 cm(-1)). The oxidation of adsorbed cyanide on the Pt(100) elec trode produces CO2 (band at 2344 cm(-1)) and adsorbed NO (band at 1624 cm(-1)), which shows a characteristic voltammetric behavior. Adsorbed cyanate (band at 2175 cm(-1)) was also identified as an intermediate product during adsorbed cyanide oxidation on Pt(100). Finally, for Pt( 110), adsorbed cyanide is slowly desorbrd below 0.1 V (RHE). (C) 1998 Elsevier Science B.V.