Tuning the oxygen mobility of CeO2 via Bi-doping for diesel soot oxidation: Experimental and DFT studies

The oxygen mobility of Bi x Ce 1−x (x = 0, 0.1, 0.2, 0.3, 1) has been experimentally and theoretically investigated. The catalysts were synthesized by a simple co-precipitation method and used for soot combustion. As shown in Raman results, Bi 0.2 Ce 0.8 has the largest amount of oxygen vacancies. The interaction of the Bi-Ce system is also presented in the outcomes of XPS, H 2 -TPR and O 2 -TPD, as well as the increased active oxygen species caused by the weakening of the metal-oxygen bond resulting from the oxygen mobility. Additionally, the electronic transfer between the Bi and Ce and the elongation of the Ce-O reported in the DFT studies support the synergism of Bi-Ce and the tuned mobility of oxygen. Further, the decrease of formation energy of oxygen vacancies presented in Bi 0.2 Ce 0.8 in agreement with the experimental results. Moreover, the optimal adsorption capacity demonstrates excellent activity. Finally, we have well verified our previous proof that Bi 0.2 Ce 0.8 , which has a higher oxygen ion mobility, has the best catalytic performance under tight and loose conditions. Our work deepens the understanding of oxygen mobility over Bi-doped CeO 2 and provides a strategy to promote the catalytic activity by tuning the oxygen mobility. • The oxygen mobility of CeO 2 tuned by Bi ions for soot removal was investigated. • Bi-doped CeO 2 has the promoted content of oxygen vacancy and the weakened bond. • DFT calculations revealed the electron transfer and the elongated Ce-O bond. • The lower formation energy of oxygen vacancy of Bi-Ce system was also confirmed. • Bi 0.2 Ce 0.8 has the largest amount of active oxygen species and enhanced activity.