CHARACTERIZATION OF A HETEROSTRUCTURE TiO2/SnO2:F/SUBSTRATE WITH TWO DIFFERENT GEOMETRIES, PREPARED BY SPRAY PYROLYSIS TO BE USED AS PHOTOCATALYST

Abstract

Two TiO 2/ SnO 2: F /substrate hetero-structures (HS) with different geometry were deposited by spray pyrolysis. The thickness for the TiO 2 and SnO 2: F films was 3.8 μm and 2.3 μm, and the band gap energy 3.3 eV and 3.6 eV, respectively. Both films have a transmittance greater than 70% in most of the visible spectrum. The electrical resistivity of the SnO 2: F film was ρ = (1.7)×10-4Ω ⋅ cm. The surface morphology of the TiO 2 film shows hemispheric agglomerates formed by nano-metric needle/platy shaped particles that give them a porous texture much like a "ball of wool," the length of the needles is from 100 nm and its thickness close to 20 nm. The geometry of HS has an important influence on its efficiency as photocatalyst under low-powered UV radiation. One of the geometry for this HS, in which the TiO 2/ SnO 2: F interface is exposed, showed greater efficiency than the TiO 2 and SnO 2: F films separately, or than the common "sandwich" type HS geometry. Specifically, a decrease by 62% of the initial concentration of a watery solution of methylene blue (mb) of 20 ppm in approximately 5 h of UV radiation is observed for the exposed interface HS compared with less than 30% reduction observed for the common sandwich type HS.