Investigation on mechanism of photocatalytic activity enhancement of nanometer cerium-doped titania

A series of Ce-TiO₂ are prepared by the sol-gel process with ammonium cerium(IV) nitrate and tetra-n-butyl titanium as raw materials and characterized with XRD, TEM, DRS, and XPS. The aberrance (0.355) of anatase(1 0 1) plane of 0.1% Ce/TiO₂ increases compared to that of TiO₂. Cerium is found to be present as a mixture of Ce^3+/4+ oxidation states, that is, the oxidation state of some cerium in Ce-TiO₂ has changed after calcination. Ce/TiO₂ yields a large red shift compared to TiO₂. Moreover, the reflectance decreases in the visible region after cerium doped on TiO₂, and the lower the reflectance the higher the activity. Cerium appears to enhance the photocatalytic activity of Ce/TiO₂ by suppressing electron-hole recombination with electron trapping at Ce⁴⁺. 0.1% Ce/TiO₂ shows highest activity for the degradation of aqueous suspension of formaldehyde.