| Abstract
| - Even though Ce1-xTixO2 (0 ≤ x ≤ 0.4) crystallizes in the cubic fluorite structure, oxygen coordination around Ce/Ti is 4 + 4 instead of 8, leading to short and long Ce/Ti−O bonds. The longer bonds lead to weaker oxygens than in CeO2, which are more easily reducible by H2. Thus, Ce1-xTixO2 has a higher OSC than CeO2.
- We determine chemical origins of increase in the reducibility of CeO2 upon Ti substitution using acombination 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 comparedto CeO2 or TiO2. Temperature programmed reduction of CeO2, TiO2, Ce0.75Ti0.25O2 and Ce0.6Ti0.4O2 upto 700 °C in H2 gave CeO1.96, TiO1.92, Ce0.75Ti0.25O1.81, and Ce0.6Ti0.4O1.73, respectively. An extendedX-ray absorption fine structure (EXAFS) study of mixed oxides at the Ti K-egde showed that the localcoordination of Ti is 4:4, with Ti−O distances of 1.9 and 2.5 Å, respectively, which are also confirmedby our first-principles calculations. Bond valence analysis of the microscopic structure and energeticsdetermined from first principles is used to evaluate the strength of binding of different oxygen atoms andvacancies. We find the presence of strongly and weakly bound oxygens in Ce1-xTixO2, of which thelatter are responsible for the higher oxygen storage capacity in the mixed oxides than in pure CeO2.
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