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 (λ > 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