MONITORING HYDROUS METAL-OXIDE SURFACE-CHARGE AND ADSORPTION BY STIRS

The first in situ infrared spectroscopic measurements of surface exces s solvated ion concentrations in the electrical double layer resulting from metal oxide surface charge are reported. Enhanced concentrations of perchlorate and tetramethylammonium ions have been detected at the surface of a TiO2 gel film. Anew technique, surface titration by inte rnal reflection spectroscopy (STIRS), has been used in which spectra a re recorded after flow-induced, stepwise pH changes. A measured isoele ctric point for TiO2 of 5 concurs with those from other methods. The p erturbing effect of specific adsorption on the TiO2 surface charge is clearly indicated by the STIRS spectra of the system containing oxalat e ion.