The controlled engineering of surface oxygen defects on Bi₂Zr₂O₇ compounds for catalytic soot combustion by adjusting...

The quantity of surface oxygen vacancies/defects is critical to promote the reactivity of metal oxide catalysts. Therefore, for the controlled engineering of Bi₂Zr₂O₇ with rich surface defects for soot combustion, four different methods have been adopted. Bi₂Zr₂O₇ compounds with a defective fluorite phase but with varied surface vacancy concentrations have been successfully synthesized by various methods. The best catalyst (Bi₂Zr₂O₇-CP) was fabricated by a facile co-precipitation method. Both O₂^- and O₂^2- were the active surface sites whose number positively correlated to the number of surface oxygen vacancies and determined the activity. Moreover, a sample with more surface vacancies usually had weaker Zr-O bonds, which could be the intrinsic factor to enhance the activity. In addition, a novel and simple method has been developed to accurately titrate the absolute amount of soot reactive oxygen sites and calculate the TOF values. In conclusion, by optimizing the preparation methods, Bi₂Zr₂O₇ catalysts with rich surface defects can be tuned, which may help in designing more applicable soot oxidation catalysts.