Structure and redox properties of CexTi1-xO2 solid solution

A series of CexTi1-xO2 mixed oxide materials was synthesized by a sol-gel method with it: varying from 0.1 to 0.9 and characterized by XRD, Raman, and TPR techniques. The structure of the mixed oxides changes with the Ce/Ti ratio. When the x value is decreased from 1.0 to 0.6 for CexTi1-xO2, only a cubic phase is detected, and the lattice parameter of the cubic phase decreases because of the formation of a solid solution by substituting Ti atoms into a CeO2 lattice. When x = 0.3, a new phase is observed. The structure of this new phase was characterized by Rietveld refinement of X-ray diffraction data. This mixed oxide adopts the monoclinic symmetry with the space group C2/m and a = 0.9811(8) nm, b = 0.3726(3) nm, c = 0.6831(6) nm, and beta = 118.84 degrees. When x = 0.4 and 0.5, a mixed phase region is detected. The addition of Ti atoms into CeO2 significantly improves the storage capacity of mobile oxygen of CeO2 by increasing the reduction extent of the mixed oxides. When x = 0.3-0.6, the valence value of Ce after a TPR run is estimated to be close to +3, which obviously is smaller than that for reduced CeO2 alone. The Ce0.5Ti0.5O2 sample shows the highest capacity of storage oxygen among CexTi1-xO2 mixed oxides. The capacity for reoxidation of the reduced CeO2-rich solid solution is higher than that of CeO2-lean mixed oxides. CexTi1-xO2 mixed oxides are promising materials for oxygen storage as well as catalysts for many reactions involving oxygen, such as the catalysts for a three-way reaction to reduce the pollutant emissions or combustion of volatile organic compounds.