Effect of single-cation doping and codoping with Mn and Fe on the photocatalytic performance of TiO2 thin films

TiO2 thin films with varying Mn and Fe dopant levels (0.01-5.00 mol% metal basis; single cation doping and codoping) were deposited on soda-lime-silica glass substrates by spin coating, followed by annealing in air at 450 °C for 2 h. The mineralogical, morphological, optical, and photocatalytic properties of the thin films were determined. The fabricated films were ∼250 nm thick and they were comprised of grains of ∼20-30 nm size. Anatase (or amorphous titania) was the only phase in essentially all the films, with the dopants' being soluble in anatase. All of the films were transparent (∼80%) in the visible region and the optical indirect band gaps were ∼3.4 eV. Photocatalytic testing (≤24 h) showed that the extent of photodegradation decreased with increasing dopant levels. The 0.01 mol% Fe-doped sample showed the best photoactivity since, at this doping level, the negative effects of electron/hole recombination and lattice distortion probably were minimal.