Flame-made visible light active TiO2:Cr photocatalysts: Correlation between structural, optical and photocatalytic properties

TiO2:Cr nanoparticles with dopant concentration from 0.1 to 10 at.% were synthesized by a liquid-fed one-step flame spray synthesis. All investigated nanopowders were synthesized with a specific surface area of about 60 m2 g−1. Undoped flame-made TiO2 consisted mainly of anatase. The increase of Cr content in TiO2:Cr nanopowder was accompanied by a decrease of the anatase phase and a consequent increase of the rutile polymorph. The comparison of the XANES spectra of samples with different doping level of Cr showed that Cr is incorporated in the structure. The presence and the concentration of Cr significantly affected the optical properties of TiO2 and caused a red-shift of the fundamental absorption edge. Photocatalytic performance of TiO2 for the gas phase formaldehyde decomposition under visible light irradiation was enhanced by Cr doping and reached its maximum at 3 at.% Cr.