INFRARED SPECTROELECTROCHEMICAL MEASUREMENTS OF THE ELECTROCHEMICAL DOUBLE-LAYER - USING CARBON-MONOXIDE AS A DOUBLE-LAYER PROBE MOLECULE

The utility of infrared spectroelectrochemical measurements to provide information about the electrochemical interface has been previously demonstrated. The use of small adsorbate molecules as probes of the interface has only recently been investigated. The infrared spectroscopic behavior of adsorbed carbon monoxide in the presence of methanol, ethanol, n-propanol, isopropanol, and ethylene glycol as well as in alcohol/water binary solvent mixtures is presented. Changes in the Stark tuning rate for the adsorbed CO are correlated with solvent dipole reorganization in methanol, ethanol, and n-propanol. No change was observed for ethylene glycol or isopropanol. For the binary mixtures, a dramatic change in the Stark tuning rate was observed as the percentage of water in the bulk mixture was altered. This observation was interpreted as a rearrangement of the solvent composition at the layer of molecules adjacent to the adsorbed CO. In the ethylene glycol/water mixture, no change in the tuning rate was observed up to 60% ethylene glycol/40% water. © 1990.