Infrared Spectroscopy of the TiO₂/Aqueous Solution Interface

Abstract

An innovative approach has been used to probe the molecular nature of the metal oxide/aqueous solution interface. Internal reflection spectroscopy of thin colloidal TiO2 films, under aqueous solutions of pH 11.7−2.3, has been used to obtain differential in situ infrared spectra related to interfacial species. An alkaline solution wash of the TiO2 films was shown to remove contaminants arising from the sol evaporation−film deposition process. Specific infrared absorptions have been assigned to terminal Ti−OH and Ti−OH2 +, adsorbed water Ti−OH2, and bridging Ti−OH+−Ti species from the pH dependence of spectra and from deuteration experiments. These surface species determine the pH-dependent surface charge and the enhanced interfacial ionic concentrations observed in our previously published STIRS results. The enhanced interfacial ionic concentrations were also observed to have spectral effects related to interfacial water structure which are similar to those observed from concentrated aqueous solutions containing these ions. The proposed interfacial species have long been components of models of hydrous oxide surfaces, but this is the first in situ vibrational spectroscopic analysis aimed at their identification.

Adsorption and surface oxidation of Fe(II) on metal (hydr)oxides

“…The estimated affinity constants explain the experimental PZC (Hiemstra et al, 1996b;Machesky et al, 2001) and also explain semi-quantitatively the in-situ IR absorption behavior observed by (Connor et al, 1999a) as discussed in Hiemstra and van Riemsdijk (2002).…”

Inner-sphere complexation of cations at the rutile–water interface: A concise surface structural interpretation with the CD and MUSIC model

“…This reflects that the bridged group is more acidic than the terminal group according to the MUSIC model, and IR spectroscopy results independently support this contention (Connor et al, 1999). Uncomplexed Ti 2 O À0.555 sites decreased in abundance as pH increased primarily due to tetradentate and/or bidentate cation binding.…”

Characterization of UOP IONSIV IE-911

“…[12][13][14] These broad bands are observed in IE-911 (binder plus CST), acid and NaOH-treated forms. In IE-910, the bands of the Si-Ti-Nb-O CST framework below 1200 cm -1 are relatively sharp, since CST is a crystalline (ordered) material.…”