Zno and SnO2 Composite Thin Film for Photocatalysis Application
Arven I. Cafe1*, Evelyn Navarro2, Debinya Buenafe1,2, Yuta Rola2, Efren Suratos1,2, Christopher Jude Vergara1,2, Laureen Ida Ballesteros1,2, Elmer Estacio1,2, Armando Somintac1
1National Institute of Physics, University of the Philippines-Diliman, Quezon City, Philippines
2Material Science and Engineering Program, University of the Philippines-Diliman, Quezon City, Philippines
* presenting author:Arven Cafe, email:acafe@nip.upd.edu.ph
Photodegredation process is highly dependent on the compatibility of the dye and the photocatalyst material being used. Using a composite material as photocatalyst, its capabilities can be expanded and the selective reaction can be optimized. In this study, the combination of Zinc oxide (ZnO) and Tin dioxide (SnO2) was used as photocatalyst for water treatment application. The transparent composite thin films were effectively deposited to a glass substrate via chemical spray pyrolysis with substrate temperature of 350oC. The volumetric ratio of ZnO:SnO2 precursor solution and post annealing temperature was varied to determine the effective growth conditions. To provide relatively better photodegradation capabilities than the homogeneous films, the surface morphology, crystallinity and optical properties of ZnO:SnO2 composite thin films were analyzed and optimized in parallel to the photodegradation mechanism.
Using the transmittance spectra, the calculated optical bandgap of the ZnO:SnO2 composite films are ranging from 3.91eV to 3.94eV. These values are relatively close to the bandgap of homogeneous SnO2 film (3.95eV) but still higher than ZnO bandgap (3.26eV). Moreover, the transparency of the composite films was observed to be 18% higher for SnO2 and 140% higher for ZnO at wavelength region from 300nm to 400nm. This suggests that the originally sufficient energy from the excitation source will be transmitted rather than being absorbed. Initial tests using methylene blue as a trial contaminant in water shows that for the first 60 minutes of UV irradiation, the degradation efficiency of homogeneous SnO2 film improved from 18% to 36% in the presence of ZnO (degradation from 9.3ppm to 6.0ppm of methylene blue). Hence, ZnO:SnO2 composite films adapted the photocatalytic and optical properties of both materials.

Keywords: photocatalysis, composite material, spray pyrolysis, transparent thin-film