INFRARED REFLECTION ABSORPTION-SPECTRA OF CYANIDE ION ADSORBED ON A PLATINUM-ELECTRODE IN SODIUM-PERCHLORATE SOLUTION

In-situ IR spectra of adsorbed cyanide ion on a platinum electrode have been ivestigated by PM-IRAS (polarization modulation infrared reflection absorption spectroscopy) in the bulk CN concentration range of 0.04-10 mM. The absorption band of the C-N stretching vibration of adsorbed CN- was found at around 2070 cm-1 in less dilute solution, the band position being dependent on both the CN- concentration and the electrode potential; it shifted to the higher wavenumber side at more positive potentials and higher CN- concentrations. In the extremely low CN- concentration range of 10(-5)-(10-4) M, however, a new band appeared at around 1980 cm-1, whose peak position was dependent only on the CN- concentration. The new band was considered to be due to bridged-type CN- adsorbed on a Pt electrode and occupying two sites.