Efficiency of cathodic arc-grown N-doped TiO2 films for the photocatalytic reduction of Cr(VI) under UV-Vis irradiation

Abstract

The photocatalytic activity of undoped and N-doped TiO2 anatase films with different thicknesses prepared by cathodic arc deposition on glass substrates is reported. After TiO2 deposition, the doping of the films was carried out by plasma immersion ion implantation in a nitrogen environment. The composition of the films was studied by x-ray photoelectron spectroscopy, the surface morphology was analyzed by atomic force microscopy and the crystalline structure was examined by x-ray diffraction. The thickness was determined by observing the film cross section with scanning electron microscopy. The transmittance of the films in the UV-Vis range was studied as well. The photocatalytic activity of the films was evaluated through the efficiency in the reduction of Cr(VI) in the presence of ethylenediaminetetraacetic acid under UV-Vis irradiation. N-doped films presented a higher photocatalytic efficiency than undoped films: Cr(VI) reduction after 5 h irradiation augmented from 58% (pure TiO2) to 85% (N-doped TiO2) for films of 300 nm thickness, and from 69% to 85% for films with a thickness of 440 nm. On the other hand, pure TiO2 films of 790 nm thickness were more efficient (99% of Cr(VI) reduction) but the effect of doping on the photocatalytic activity was negligible.