Correlation of the crystal structure of titanium dioxide prepared from titanium tetra-2-propoxide with the photocatalytic activity for redox reactions in aqueous propan-2-ol and silver salt solutions

Abstract

Titanium dioxide (TiO₂) has been prepared by the hydrolysis of titanium tetra-2-propoxide, followed by calcination at various temperatures (T_c) up to 1000 °C. The content and crystallite size of anatase in the TiO₂ powders increased upon increasing T_c up to 550 °C. In the T_c range 550–600 °C a mixture of anatase and rutile was obtained. A further increase in T_c resulted in TiO₂ of rutile structure only. The photocatalytic activities of these TiO₂ powders for redox reactions were evaluated in the following systems: (1) aqueous propan-2-ol solution, (2) aqueous Ag₂SO₄ solution and (3) aqueous Ag₂SO₄ solution containing propan-2-ol. The anatase TiO₂ showed photocatalytic activity in all these systems, the activity increasing with crystal growth. In aqueous propan-2-ol solution the activity is dramatically enhanced by partial coverage of the TiO₂ with platinum black. The photocatalytic activity of the rutile TiO₂ powder was comparable to or even greater than that of anatase when the reaction system included the silver salt, but was negligibly small for aqueous propan-2-ol solution regardless of the partial Pt coverage.