Enhanced oxygen storage capacity of CeO2 with doping-induced unstable crystal structure

Highlights: • OSC of CeO₂ was efficiently enhanced by doping-induced unstable crystal structure. • Oxygen vacancy content was adjusted by manipulation of crystal structure parameter. • Low temperature OSC of Hf-doped CeO₂ was 2.2 times as high as that of undoped CeO₂. • Linear functions of composition vs. lattice parameter, defect vs. OSC were gotten. • Quantitative structure-performance relationships of CeO₂ catalyst were constructed. Doping CeO₂ with certain metallic ions has been shown to be an effective route to improving its oxygen storage capacity (OSC). We aimed to study the effects of dopants on the OSC of CeO₂ from the perspective of crystallography. In the present study, we improved the OSC by construction of an extremely unstable CeO₂ crystal structure based on crystallographic principles. By doping CeO₂ with smaller Hf⁴⁺ and Sn⁴⁺ cations, the incorporated cations produced a lower cation to anion radius ratio in the crystal. The relative oxygen vacancy concentrations were 0.452 and 0.514, respectively, for 3 mol.% doping of Hf⁴⁺ and Sn⁴⁺, respectively. Our results showed that smaller dopant cations (radius of Sn⁴⁺ < Hf⁴⁺) led to more vacancies. The low temperature OSC of a CeO₂ sample doped with a saturated amount of Hf⁴⁺ was 2.2 times as high as that of undoped CeO₂ with a similar BET specific surface area. The partial least squares method was used to construct two linear functions for the Hf⁴⁺- and Sn⁴⁺-doping concentration vs. lattice parameters, and the relative oxygen vacancy concentration vs. low temperature OSC per BET surface area. Structure-performance relationships were developed to enable the design of CeO₂ three-way catalysts.