Synthesis of TiO2 on SnO2 bicomponent system and investigation of its structure and photocatalytic activity

Photocatalytically visible light active thin SnO2/TiO2 bicomponent coatings with SnO2 underlayer, were deposited by spray pyrolysis. XRD, AFM, XPS and DRS analyses were used to characterize their morphology, phase and chemical composition, structure and band gap width. The model wastewater contaminant was diazo dye and the photocatalytic properties were tested by discoloration oxidation reaction. The photocatalytic activity of the SnO2/TiO2 system depends on the SnO2 precursor solution parameters: sprayed volume and the concentration of the SnO2 solution. It was revealed that the bicomponent coatings with SnO 2 underlayer, which has been prepared at large spray solution volume and low tin precursor concentration exhibit increased photocatalytic activity. The combination of several factors ensures high rate of the oxidative reaction of degradation: the lower recombination degree of electron-hole pairs due to the separation of charge-carriers; decreased band gap energy, higher roughness and larger content of hydroxil groups on the surface of SnO2/TiO2 bilayers in comparison to the TiO2 films as well as the synergism between anatase and rutile phases.