An experimental and theoretical study of the effect of Ce doping in ZnO/CNT composite thin film with enhanced visible light photo-catalysis

Abstract

Ce-doped ZnO/CNT composite thin film was fabricated successfully on soda-lime-silica glass substrate by sol-gel drop coating method. The structure and morphology of nanocrystalline Ce-doped ZnO/CNT thin film were characterized by X-ray Diffraction (XRD), X-ray photo-electron spectroscopy (XPS), Field Emission Scanning Electron Microscope (FESEM) and UV–Visible spectroscopy. The photocatalytic activity of Ce-doped ZnO/CNT thin film was evaluated by photocatalytic degradation of methylene blue (MB) in aqueous solution as a model pollutant under visible light irradiation. The synthesized Ce-doped ZnO/CNT composite thin film showed 76.71% photocatalytic efficiency whereas bare ZnO thin film showed that of only 25.30%. It has been reported that improved photocatalytic efficiency of composite is due to the synergistic effect of Ce doping and insertion of CNTs into ZnO matrix. The experimental photodegradation data were well fitted to first-order kinetics. The photocatalytic activity of the prepared thin film can be regenerated, which implies that the photocatalytic degradation process could be operated at a relatively low cost. The results suggest that Ce-doped ZnO/CNT composite thin film prepared by sol-gel drop coating method can be developed as an economically feasible and environmentally friendly method to degrade dye containing wastewater using visible light. Furthermore, atomic models for Ce doping in ZnO cluster was used to investigate the effect of doping on electronic structure of ZnO through density functional theory calculations. The computational study suggested a significant narrowing of the band gap and change of the maximum absorption bands towards higher wavelength. These all support the experimental results.