Synthesis and characterization of immobilized titanium-zirconium Sn-doped oxides onto metallic meshes and their photocatalytic activity for erythromycin mineralization

An improvement of the photocatalytic properties of TiO2, by the doping with Sn, a non-critical raw material, was evaluated. A series of Sn-doped titania-zirconia structured photocatalysts were synthesized using the washcoating method on stainless steel meshes. Two methodologies for the Sn incorporation were applied using different Sn sources: oxalate and SnO2 (powder or nanoparticles). Coating properties were characterized by SEMEDS, XPS and LRS techniques, and their photocatalytic performances were tested for erythromycin (ERY) oxidation. The coating synthesized with the Sn-oxalate suspension presented a more homogeneous distribution of the elements. Surface characterization showed that the Sn-doped catalysts presented a partial reduction of the Ti4+ species to Ti3+ with the presence of some oxygen vacancies, associated to an effective interaction between Ti and Sn (surface Ti1-xSnxO2-like structure). The lowest amount of these vacancies were found when the Sn source was SnO2 (powder or nanoparticles). The formation of a Ti-Sn-O solid solution decreased the recombination of the e-cb/h+vb pair, allowing better performance on the photocatalytic degradation of ERY, with 46% mineralization for the Sn doped photocatalyst and 26% for the Sn-free catalyst. The Sn addition methodology influenced the catalytic activity due to the formation of different oxidizing agents, leading to different carboxylic acids generation. The best photocatalyst presented after more than 400 h of use, a catalytic activity decreases of only 11.3% in mineralization, showing that this photocatalyst has a high catalytic stability. Besides, after a regeneration process, the catalytic activity was almost thoroughly recovered.