Solvothermal Synthesis, Structural Characterization and Optical Properties of Pr-Doped CeO2 and Their Degradation for Acid Orange 7

Pr-doped CeO2 with different doping levels was prepared from Ce(NO3)3∙6H2O and Pr(NO3)3∙6H2O by solvothermal method without any additional reagents, in which the mixed solution of ethylene glycol and distilled water was employed as a solvent. The influences of Pr-doping on phase composition, crystal structure and morphology were investigated, as well as Pr valence and oxygen vacancy defects. The Pr cations entered into the CeO2 crystal lattice with normal trivalence and formed a Pr-CeO2 solid solution based on the fluorite structure. The larger trivalent Pr was substituted for tetravalent Ce in the CeO2 crystal and compensated by oxygen vacancy defects, which caused the local lattice expansion of the crystal lattice. Moreover, the Pr-doped CeO2 solid solutions exhibited visible color variation from bright cream via brick red to dark brown with the increasing of Pr contents. The degradation of AO7 dye was also investigated using a domestic medical ultraviolet lamp; the removal efficiency of AO7 by 1% and 2% Pr-doped CeO2 approached 100%, much higher than 66.2% for undoped CeO2