Multiple Internal Reflection Fourier Transform Infrared Spectroscopy Studies of Thiocyanate Adsorption on Silver and Gold

Conducting silver and gold coatings on silicon Attenuated Total Reflectance (ATR) plates have been employed as transparent electrodes to monitor in situ surface electrochemistry. The multiple internal reflection Fourier transform infrared spectroscopy (MIRFTIRS) technique, used previously to study redox reactions on platinum and iron films, is applied in this work to the study of adsorption processes in the double-layer region, in particular, the adsorption of thiocyanate on silver and gold. The MIRFTIRS spectra were found to be essentially free of solution band interference and are compared to surface IR spectra of the same system obtained by other methods. Spectra of thiocyanate adsorbed on gold and silver surfaces have been recorded as a function of applied potential and thiocyanate concentration. Evidence of thiocyanate species absorbed to gold via both nitrogen and sulfur atoms has been obtained, while only S-bound thiocyanate was clearly observed on silver.