Synthesis of Li-doped ZnO via sol-gel process: structural, optical and photocatalytic properties

In this work, the sol-gel technique was carried out to prepare lithium doped ZnO materials with a controlled percentage (3-10 %). The changes in structural, optical and photocatalytic properties were investigated using X-ray powder diffraction, FT-IR spectroscopy, diffuse reflectance UV-visible and scanning/transmission electron microscope. X-ray diffraction showed that ZnO nanoparticles exhibit hexagonal wurtzite structure. The calculated average crystalline size increases from 30 nm of ZnO and 40 nm of ZnO-Li (10 %). The UV peaks positions of the modified samples shifted towards the longer wavelength compared to pure ZnO. The optical band gap of the samples was found to be 3.24 eV for ZnO-Li (3 %) and 3.28 eV for ZnO-Li (10 %), which proves the change in the acceptor level induced by the Li atoms. For the application, the evaluation of the photocatalytic activity is carried out using p-nitrophenol (p-NP) as a model of chemical pollutants. As result, Li doped ZnO materials displayed photocatalytic activity is less than pure ZnO, due to the Li atom that increases the recombination rate of electron-hole pairs, which decreases the photocatalytic activity.