Preparation of Sn4+-Doped Titanium Dioxide Photocatalytic Films on 304 Stainless Steel by Duplex Treatment

Sn4+-doped titanium dioxide photocatalytic films were synthesized on 304 stainless steel (SS) by a duplex treatment. The SS substrates were alloyed with titanium (Ti) through cathodic-arc ion plating followed by a microarc oxidation (MAO) treatment in different electrolytes. Field-emission scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy were used to characterize the films surface morphology, crystalline phase, and composition, respectively. Photocatalytic activity was measured using an UV-Vis spectrophotometer. It was found that the films with a porous structure are mainly composed of TiO2, which exists in an anatase and rutile state. Furthermore, small quantities of SnO2 have been found in the Sn4+-doped titanium dioxide films. The fraction of anatase varies with the MAO time and electrolytes, whereas the pore size remains the similar with the same MAO current intensity and density and the surface roughness increases slightly with increasing MAO time. It was also found that the photocatalytic activity of the Sn4+-doped porous film improved, and the film synthesized with a shorter MAO time in a lower Na2SnO3-containing electrolyte is superior to the films with longer MAO times and higher Na2SnO3 concentrations.