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

This work reports an alternative preparation and evaluation of nanocrystalline N-modified CeO 2 as a visible-light-active photocatalyst . Nanocrystalline N-modified CeO 2 (which was abbreviated as CeO 2 –HNO 3 ) was synthesized directly via the solvothermal reactions of Ce(NO 3 ) 3 ·6H 2 O, concentrated (65–68 mass%) HNO 3 and toluene at 180   °C for 24   h. The composition, structure and optical property of CeO 2 –HNO 3 were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of CeO 2 –HNO 3 was tested in the reduction of aqueous Cr 6+ under visible-light ( λ >420   nm) irradiation, and compared with that of CeO 2 –NH 3 (which denoted the product prepared when 25-28 mass% NH 3 ·H 2 O replaced 65–68 mass% HNO 3 ). It was observed that CeO 2 –HNO 3 exhibited much higher photocatalytic activity than CeO 2 –NH 3 in the reduction of aqueous Cr 6+ under visible-light ( λ >420   nm) irradiation. CeO 2 –HNO 3 may be a new promising visible-light-active photocatalyst in efficient utilization of solar energy for treating Cr 6+ wastewater.