Combustion synthesis of TiO2 nanoparticles as photocatalyst

This paper describes a new type of combustion synthesis of metal oxide nanoparticles, in which the adiabatic flame temperature of the solid phase reaction is beyond the boiling point of the product, and its implementation for the synthesis of titanium dioxide as photocatalyst. In this study, raw materials comprising titanium particles of different sizes and sodium perchlorate were intensively mixed and ignited by an electrical heating foil to produce titanium dioxide through the following reaction: Ti + NaClO4 → TiO2 + NaCl. The shape and crystal structure of the titanium dioxide product significantly depended on the particle size of the titanium used as raw material. That is, the smaller titanium particles (average size (AS) of 10 μm) resulted in rutile with an irregular shape, whereas the larger particles (AS of 25 μm) resulted in spheres of anatase. The photocatalytic activities of these samples were evaluated using the photocatalytic reactions of aqueous titanium dioxide suspensions containing methanol and acetic acid by irradiation at 298 K in argon atmosphere or in air. The activity of the rutile-rich sample was significantly larger than that of the anatase-rich one in both photocatalytic reactions.