Origin of enhanced reducibility/oxygen storage capacity of Ce1-xTixO2 compared to CeO2 or TiO2

被引:182
作者
Dutta, Gargi
Waghmare, Umesh V.
Baidya, Tinku
Hegde, M. S. [1 ]
Priolkar, K. R.
Sarode, P. R.
机构
[1] Indian Inst Sci, Solid State & Struc Chem Unit, Bangalore 560012, Karnataka, India
[2] Indian Inst Sci, Jawaharlal Nehru Ctr Adv Sci Res, Theoret Sci Unit, Bangalore 560012, Karnataka, India
[3] Goa Univ, Dept Phys, Taleigao Plateau 403206, Goa, India
关键词
D O I
10.1021/cm060267i
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We determine chemical origins of increase in the reducibility of CeO2 upon Ti substitution using a combination of experiments and first-principles density functional theory calculations. Ce1-xTixO2 ( x = 0.0-0.4) prepared by a single step solution combustion method crystallizes in a cubic fluorite structure, confirmed by Rietveld profile analysis. Ce1-xTixO2 can be reduced by hydrogen to a larger extent compared to CeO2 or TiO2. Temperature programmed reduction of CeO2, TiO2, Ce0.75Ti0.25O2 and Ce0.6Ti0.4O2 up to 700 degrees C in H-2 gave CeO1.96, TiO1.92, Ce0.75Ti0.25O1.81, and Ce0.6Ti0.4O1.73, respectively. An extended X-ray absorption fine structure ( EXAFS) study of mixed oxides at the Ti K-egde showed that the local coordination of Ti is 4: 4, with Ti-O distances of 1.9 and 2.5 angstrom, respectively, which are also confirmed by our first-principles calculations. Bond valence analysis of the microscopic structure and energetics determined from first principles is used to evaluate the strength of binding of different oxygen atoms and vacancies. We find the presence of strongly and weakly bound oxygens in Ce1-xTixO2, of which the latter are responsible for the higher oxygen storage capacity in the mixed oxides than in pure CeO2.
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页码:3249 / 3256
页数:8
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