N, Fe single-doped and N-Fe co-doped TiO2 powders and films increasing photoactivity under visible light

This study aims to develop an eco-friendly and efficient photocatalytic coat-ing, active under a cost-effective visible LED system for the removal of or-ganic pollutants. An aqueous sol-gel process has been used to produce N or Fe single-doped TiO2 photocatalysts as well as N-Fe co-doped TiO2 catalysts to extend its activity in the visible region. The physico-chemical properties of those catalysts were characterized by X-ray diffraction and diffuse reflec-tance spectroscopy and compared to commercial Evonik P25 TiO2. The use of dopants (N or Fe) extends the activity of TiO2 towards visible range.
The photocatalytic activity of the undoped and doped catalysts has been studied by evaluating the degradation of the p-nitrophenol under visible light ( > 395 nm). Results show the increase of the p-nitrophenol degradation under visible light for all photocatalysts compared to undoped of commercial P25 TiO2, with the best results for the N-Fe co-doped TiO2 catalysts. Colloids prepared from these powders were spray-coated onto stainless steel sub-strates. After a large number of optimizations of the number of layers, of the roughness of the films, of the operating conditions of the spray-coating, a complete degradation of p-nitrophenol was obtained in 4 h at 18 °C with the TiO2-based coating doped with 43%mol of nitrogen and 0.25%mol of iron, and having an average thickness around 2 µm.