Accession Number : ADA117891

Title :   Characterization of Species Adsorbed on Oxidized and Reduced Anatase.

Descriptive Note : Technical rept. 1 Jan-1 Dec 82,


Personal Author(s) : Tanaka,Katsumi ; White,J M

PDF Url : ADA117891

Report Date : 23 Jul 1982

Pagination or Media Count : 19

Abstract : The adsorption of water, pyridine carbon dioxide and carbon monoxide were studied by infrared absorption spectroscopy on reduced and oxidized anatase. There are two kinds of isolated OH groups, as well as two kinds of adsorbed water molecules, for the anatase powders used in this study. These species are assigned to adsorption on different crystal faces. The water and hydroxyl species are more stable on oxidized anatase. Some sites where OH groups are readily formed are thought to have different coordination as compared to sites where water is held. The coordination number of the Ti ions is 4 for water adsorption and 4 or 5 for OH. No surface Bronsted acidity is detected by pyridine adsorption. The surface hydroxyl groups, working as OH minus react with coordinated C02 to form carbonate species when the oxidized surfaces are exposed to C02. The resulting bicarbonate species decompose to form water molecules which, upon evacuation, dissociate to some extent so that OH groups are partially recovered. On oxidized anatase, room temperature CO exposure gave rise to some surface reduction and two different kinds of adsorbed CO were detected. (Author)

Descriptors :   *Titanium dioxide, *Crystals, *Adsorption, Infrared spectroscopy, Water, Pyridines, Carbon dioxide, Carbon monoxide, Hydroxyl radicals, Molecules, Surface chemistry, Oxidation, Reduction(Chemistry)

Subject Categories : Crystallography
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE