Thin films of photocatalytic TiO2 and ZnO deposited inside a tubing by spray pyrolysis

Thin films of photocatalytic TiO2 and ZnO were deposited in Vycor tubing by a simple and reproducible spray pyrolysis technique. Films were transparent and non-light scattering. Film characterization by transmission electron microscopy shows that titanium oxide films were polycrystalline and that their structure corresponded to the tetragonal anatase phase, In addition, ZnO films were polycrystalline with a structure that belonged to the hexagonal Wurtzite type, The solar photocatalytic efficiency for butane degradation was compared to that of Degussa P-25 TiO2 powder (P-25). Reaction rate and reaction order were obtained from butane concentration measurements using the tubing as a non-circulating reactor exposed to solar radiation, The best fitting was obtained for a pseudo-first order rate constant. The TiO2-covered tubing shows very high photocatalytic activity, even higher than that of P-25, if activity per unit of catalyst mass is considered. (C) 2002 Elsevier Science B.V. All rights reserved.