HNO3-involved one-step solvothermal preparation of nanocrystalline N-modified CeO2 with enhanced visible-light activity

• Nanocrystalline N-modified CeO2 was prepared by a HNO3-involved solvothermal method.
• Strong and wide absorption of visible-light.
• High photocatalytic activity in the reduction of aqueous Cr6+ under visible-light.

This work reports an alternative preparation and evaluation of nanocrystalline N-modified CeO2 as a visible-light-active photocatalyst. Nanocrystalline N-modified CeO2 (which was abbreviated as CeO2–HNO3) was synthesized directly via the solvothermal reactions of Ce(NO3)3·6H2O, concentrated (65–68 mass%) HNO3 and toluene at 180 °C for 24 h. The composition, structure and optical property of CeO2–HNO3 were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of CeO2–HNO3 was tested in the reduction of aqueous Cr6+ under visible-light (λ>420 nm) irradiation, and compared with that of CeO2–NH3 (which denoted the product prepared when 25-28 mass% NH3·H2O replaced 65–68 mass% HNO3). It was observed that CeO2–HNO3 exhibited much higher photocatalytic activity than CeO2–NH3 in the reduction of aqueous Cr6+ under visible-light (λ>420 nm) irradiation. CeO2–HNO3 may be a new promising visible-light-active photocatalyst in efficient utilization of solar energy for treating Cr6+ wastewater.