Abstract: Using ethylene glycol, water and propanoic acid as solvent, precursor with sheet and sphere shape was first synthesized by template-free solvothermal method through varying the volume ratio of ethylene glycol under 180 ℃.Then CeO2 nano-sphere and nano-sheet was prepared by calcinating the precursor at 500 ℃ for 2 h in the air.The properties of the samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Ultraviolet-visible spectroscopy (UV-Vis DRS).The photocatalytic properties to methylene blue solution were investigated under visible light irradiation.The results show that the CeO2 still kept the shape of the precursor with sheet and spherical morphology after calcination, which was assembled by nanoparticles.The diameter of CeO2 nano-sheet is 0.3-1 μm and the thickness is 20-60 nm.The diameter of CeO2 nano-sphere is about 120-200 nm.CeO2 nanostructures could decrease the band gap energy, increase the specific surface and make the absorption edges red shifting, which significantly increase the photocatalytic activity.The photocatalytic degradation rate of MB in 3 h increased from 12.3; for rod-like CeO2 to 80.1; for CeO2 nano-sphere and 91.2; for CeO2 nano-sphere, respectively.

Key words: Using ethylene glycol, water and propanoic acid as solvent, precursor with sheet and sphere shape was first synthesized by template-free solvothermal method through varying the volume ratio of ethylene glycol under 180 ℃.Then CeO2 nano-sphere and nano-sheet was prepared by calcinating the precursor at 500 ℃ for 2 h in the air.The properties of the samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Ultraviolet-visible spectroscopy (UV-Vis DRS).The photocatalytic properties to methylene blue solution were investigated under visible light irradiation.The results show that the CeO2 still kept the shape of the precursor with sheet and spherical morphology after calcination, which was assembled by nanoparticles.The diameter of CeO2 nano-sheet is 0.3-1 μm and the thickness is 20-60 nm.The diameter of CeO2 nano-sphere is about 120-200 nm.CeO2 nanostructures could decrease the band gap energy, increase the specific surface and make the absorption edges red shifting, which significantly increase the photocatalytic activity.The photocatalytic degradation rate of MB in 3 h increased from 12.3; for rod-like CeO2 to 80.1; for CeO2 nano-sphere and 91.2; for CeO2 nano-sphere, respectively.