A STRUCTURAL INVESTIGATION OF TITANIUM-DIOXIDE PHOTOCATALYSTS

A study of the structure and the morphology of a titanium dioxide photocatalyst (Degussa P25) reveals multiphasic material consisting of an amorphous state, together with the crystalline phases anatase and rutile in the approximate proportions 80 20. Transmission electron microscopy provides evidence that some individual particles are a mixture of the amorphous state with either the anatase phase or with the rutile phase, and that some particles, which are mostly anatase, are covered by a thin overlayer of rutile which manifests its presence by the appearance of Moiré fringes. The photocatalytic activity of this form of titanium dioxide is reported as being greater than the activities of either of the pure crystalline phases, and an interpretation of this observation has been given in terms of the enhancement in the magnitude of the space-charge potential, which is created by contact between the different phases present and by the presence of localized electronic states from the amorphous phase. © 1991.