Photocatalytic activity of hierarchically structured, thermally stable, anatase particles

In order to avoid the potential health problems associated with nanosized particles, solvothermal synthesis was employed for the preparation of doped and undoped, hierarchically structured, spherical anatase, ranging in size from 2 to 6.4 mu m. The resulting particles showed a mesoporous microstructure and, consequently, a high specific surface area of up to 208 m(2) g(-1). A detailed SEM analysis confirmed the hierarchical structure of the spheres, consisting of subunits with a size from 10 to 21 nm, depending on the starting composition. For the thermal stabilization of the anatase phase and to slow down the growth of the nanosize particles during heating, various dopants were added to the anatase. As a result, anatase codoped with Ce, Si and Zr exhibited a high thermal stability up to 1000 degrees C, compared to 700 degrees C for the undoped anatase. The photocatalytic activities of the synthesized solids were quantitatively evaluated by monitoring the rate of degradation for isopropanol in a gas phase reactor system. Among the samples that were heat treated at 500 degrees C, the highest photocatalytic activity was exhibited by the Ce-doped sample. In the case of the samples which were heat treated at 1050 degrees C, the undoped and Ce-doped samples were inactive under UV light, while the samples doped with Ce, Zr and Si exhibited considerable photocatalytic activity.