Vibrational spectroscopy of adsorbed sulfate and nitrate ions on Au(100) electrodes

The vibrational spectra of adsorbed sulfate, bisulfate and nitrate ions on Au(100) electrodes are reported. It is found that sulfate ions present only one detectable potential dependent band located between 1150-1220 cm(-1), which has been assigned to the symmetric vibration of a C-2v or C-3v symmetry, due to the adsorption through one of two oxygen atoms. Bisulfates are partially deprotonated when adsorbed. The proton loss is a function of the applied electrode potential. For more positive potentials the proton loss increases. The band for adsorbed bisulfate ions is located at 1080-1090 cm(-1). Nitrate ions are doubly coordinated to the Au(100) surface and the spectral bands are located at 1020 cm(-1) (weak) and 1450 cm(-1).