Photodegradation of methylene blue dye using graphene oxide incorporated, post-transition metal doped zinc oxide thin films by spray pyrolysis

Photocatalytic activity of graphene oxide incorporated pure and metal doped zinc oxide thin films were studied against methylene blue dye under simulated solar irradiation. Thin films were deposited on a glass substrate using an automated spray pyrolysis technique at a temperature of 425 degrees C. Aluminium, gallium, and indium were the post-transition metals used for doping. Graphene oxide content in the precursor solution was fixed at 0.00375 g/l. The formation of the wurtzite structure of zinc oxide has been confirmed using structural analysis. The average crystallite size of all the thin film samples was found to be in the range of 45-55 nm. The morphology and elemental composition of the films were studied using scanning electron microscopy and energy-dispersive x-ray spectroscopy. The energy band gap of the material was determined from UV-vis-NIR spectroscopic measurements using Tauc's plot and it is in the range of 3.25-3.28 eV. Photoluminescence spectra of the as-deposited films were recorded. Intensity of the near band emission at 395 nm was found to decrease upon metal doping, indicating a better photocatalytic property. All the films were used for heterogeneous photocatalysis and the indium doped zinc oxide thin film incorporated with graphene oxide was found to be a better catalyst with an efficiency of 94.9% for degrading methylene blue dye in 180 min.