Photocatalytic activity of chemically deposited ZnO and TiO₂ nanostructured thin films in methyl orange degradation

Abstract

Water pollution caused by synthetic dyes, such as Methyl Orange (MO), represents an environmental concern due to their negative impacts on the environment and human health. The removal of these pollutants represents a challenge due to their chemical stability and resistance to conventional water treatment methods. Addressing these problems requires the development of photocatalytic materials capable of degrading this persistent pollutant. This project tests the photocatalytic activity of ZnO and TiO2 films by degrading MO solution (additionally, ZnO is used for the photodegradation of Levonorgestrel). ZnO thin films were deposited using Dip Coating and Ultrasonic Spray Pyrolysis to study the effect of precursor concentration, Ni doping, precursor milling and deposition method. Additionally, TiO2 samples were deposited only by Dip Coating to study the effects of the precursor used (titanium butoxide or titanium isopropoxide) and the water to titanium precursor ratio. The synthesized films were characterized by FTIR, XRD, SEM and UV-Vis spectroscopy. The highest MO degradation efficiency (83.75%) when using ZnO was achieved with ZnO-0.1-DC, which is attributable to its small crystallite size and particle sizes, as well as high dislocation density. Nevertheless, the ZnO thin films performed poorly during the degradation of levonorgestrel. Regarding TiO2 films, TiO2-103-BU-DC performed the best during the MO photodegradation (83.89%), which is attributable to its small crystallite size, high dislocation density and mixture phases (anatase and brookite).