Defect-Induced Band Gap Narrowed CeO2 Nanostructures for Visible Light Activities

This work reports an electron beam irradiation (30 kGy and 90 kGy) approach to narrow the band gap of the pristine CeO2 nanostructure (p-CeO2) to enhance their visible light activity through defect engineering. This was confirmed by diffuse reflectance spectroscopy, photoluminescence, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller, electrochemical impedance spectroscopy, and linear scan voltammetry. XPS revealed changes in the surface states, composition, Ce4+ to Ce3+ ratio, and other defects in the modified CeO2 nanostructures (m-CeO2). The m-CeO2 exhibits excellent photocatalytic activities by degrading 4-nitrophenol and methylene blue in the presence of visible light (lambda > 400 nm) compared to the p-CeO2. The optical, photocatalytic, and photoelectrochemical studies and proposed mechanism further support the enhanced visible light photocatalytic activities of the m-CeO2. This study confirmed that defect-induced band gap engineered m-CeO2 could be used effectively as photocatalyst and photoelectrodes owing to their enhanced visible light photocatalytic activities.