Tuning the wettability and photocatalytic efficiency of heterostructure ZnO-SnO2 composite films with annealing temperature

ZnO-SnO2 composite films were spin-coated and annealed at different temperatures. The characteristics of the films were studied by using XRD, FESEM, AFM, FT-IR and UV-Vis spectroscopy. The wetting nature of the films was assessed by observing the water contact angle by sessile drop method. It was seen that the annealing temperature had a significant role in increasing the surface roughness. This leads to a change in water contact angles which are consistent with the Wenzel state of wetting. Photodegradation of model pollutants in liquid phase (cationic methylene blue, anionic methyl orange) and solid phase (octadecanoic acid) was performed to measure the photocatalytic efficiency of the films. The enhanced photocatalytic efficiency of films annealed at higher temperatures is due to better crystallinity and formation of heterostructure that inhibits the recombination of charge entities (electron-hole).