Oxygen Gateway Effect of CeO2/La2O2SO4 Composite Oxygen Storage Materials.

Abstract

A synergistic enhancement in oxygen release/storage performance was achieved with composites formed between CeO2 as an oxygen gateway and La2O2SO4 as an oxygen reservoir. CeO2 smoothly transfers oxygen atoms between La2O2SO4 and the gas phase, whereas La2O2SO4 stores a large amount of oxygen. The composite materials exhibited enhanced anaerobic CO oxidation and reversible oxygen storage in the presence of impregnated Pt catalysts as compared to their individual constituents (Pt/CeO2 and Pt/La2O2SO4). In situ X-ray diffraction and Raman experiments demonstrated that CeO2 significantly accelerated the redox reaction between La2O2SO4 (S6+) and La2O2S (S2–), while preserving its structure. The reaction between CO and CeO2/18O-labeled La2O2SO4 composites suggested that CO mainly reacted with the lattice oxygen atoms of CeO2, and the resulting oxygen vacancies were subsequently filled with oxygen atoms supplied by La2O2SO4. This oxygen gateway effect of CeO2 greatly enhanced the oxygen release/storage rates of La2O2SO4, while maintaining the high oxygen storage capacity, which is an advanced feature of oxysulfate materials. The synergistic effect is mostly pronounced when the two different oxygen storage materials are in intimate contact to form a three-phase boundary.