Photocatalytic activity of TiO2 films prepared by cathodic arc deposition: dependence on thickness and reuse of the photocatalysts

Abstract

In this work, the photocatalytic activity of anatase films with thicknesses up to 1100 nm prepared by cathodic arc deposition (CAD) on glass substrates is reported. The photocatalytic activity under UV?Vis irradiation (λ > 330 nm) was evaluated through the efficiency in the reduction of 0.80 mM Cr(VI) in the presence of 1 mM ethylenediaminetetraacetic acid (EDTA) at pH 2, and compared with the performance of samples obtained by dip-coating using commercial P25. The CAD films were optically transparent, with visible light transmittance ≥ 50% even for the thickest samples. The photocatalytic efficiency of the films increased as the thickness increased. The possibility of obtaining thicker films allowed cathodic arc films reaching better performance than P25 samples. For the most active films obtained by CAD, complete Cr(VI) reduction could be obtained in <300 min under a 28 W m−2 UV-A irradiance. The photocatalytic reaction for all the studied TiO2 films obeyed pseudo-first order kinetics. A decrease of the reaction rate constant was observed for both types of films after reusing the photocatalysts. The fate of the reduced Cr(VI) was also analyzed.