Stabilization mechanism of TiO2 on flexible fluorocarbon films as a functional photocatalyst
The repetitive discoloration kinetics of the azo-dye Methyl Orange (taken as a model organic compound) was followed under solar simulated radiation (90 mW/cm2) to assess the performance of the TiO2/Tedlar® composite photocatalyst. The influence of solution parameters on the photo-discoloration process: pH, dye concentration, applied light intensity and concentration of H2O2 were systematically investigated. During the photocatalysis a modification occurs in the TiO2/Tedlar® composite due to the TiO2 interaction with the Tedlar® film. Physical insight is given for the stabilization mechanism of the TiO2 particles in the Tedlar matrix based on the data obtained by X-ray photoelectron spectroscopy (XPS). The F 1s peak of the Tedlar film indicates that the TiO2 is loaded on the Tedlar fluoro-groups. The loading of TiO2 on the 75 μm thick Tedlar® film was 0.9% (w/w) as determined by atomic absorption spectrophotometry (AAS). Attenuated total reflection infrared spectroscopy (ATRIR) shows no formation of additional bands within the photodiscoloration reaction. This shows that an efficient catalysis taking place on the TiO2/Tedlar® surface. The rugosity (mean square roughness, rms) of the TiO2/Tedlar® film was determined by atomic force microscopy (AFM) to be 19.7 nm. This value remained constant during long-term operation. Transmission electron microscopy (TEM) reports the thickness and coverage of TiO2 Degussa P-25 on the Tedlar® surface before and after photocatalysis.