Comparison between Real-Time Polarization Modulation and Static Linear Polarization for in Situ Infrared Spectroscopy at Electrode Surfaces

Both conventional static linear polarization selection and a new real-time sampling technique for polarization modulation were used for in situ FT-IR spectroelectrochemical studies of copper electrodes. Three aqueous probe species were investigated: thiocyanate ion, imidazole, and glucose. As the data were obtained under identical electrochemical conditions for the systems studied, a direct comparison of the optical methodologies was possible. The modulation technique provided excellent rejection of signals due to atmospheric gases and increases in overall sensitivity relative to the static method. Both techniques provided equivalent information with respect to surface species, but differed in the extent to which the electrolyte solution was sampled. Thus, by using both techniques to study a given electrochemical process, a means to discriminate spectral features due to adsorbed species from those due to solution-phase components is established.