CRYSTALLIZATION OF TITANIA IN LIQUID-MEDIA AND PHOTOCHEMICAL PROPERTIES OF CRYSTALLIZED TITANIA

Titania gels in liquid media crystallized from amorphous to anatase at temperatures as low as 120 degrees C, while the onset of crystallizat ion in air was 370 degrees C. The crystallization rate in water was mu ch faster than in methanol and n-hexane, and the crystallite size of a natase prepared in water was larger than of those prepared in organic solvents. The crystallized powders were capable of efficient hydrogen evolution following band gap irradiation in the presence of a sacrific ial hole acceptor such as methanol. The photocatalytic activity of pow der crystallized in methanol was superior to those prepared in water a nd air.