Oxygen Vacancy Promoted O-2 Activation over Perovskite Oxide for Low-Temperature CO Oxidation

The insights on the primary active oxygen specie and its relation with oxygen vacancy is essential for the design of low-temperature oxidation catalysts. Herein, oxygen vacancy-rich La0.8Sr0.2CoO3 with an ordered macroporous structure was integrated on the commercial ceramic monolith in large scale without additional adhesives via a facile in situ solution assembly. The constructed macropores not only contributed to the oxygen vacancy generation in catalyst preparation but also facilitated favorable mass transport during catalytic process. Combined with theoretical investigations and EPR, O-2-TPD, H-2-TPR observations, we revealed that monatomic oxygen ions (O-) are the primary oxygen active specie for perovskite oxide. And molecular O-2 is more favorably adsorbed and activated on surface oxygen vacancies via a one electron transfer process to form monatomic oxygen ions (O-), thus boosting richness of active O- and the low-temperature oxidation of CO. Different with the preferential Eley-Rideal (E-R) mechanism on pristine LSCO surface, Langmuir-Hinshelwood (L-H) mechanism, in which O- reacts with adsorbed CO to finish the oxidation reaction, was more favorable on the oxygen vacancy rich surface. Our work here elucidates the primary active oxygen specie as well as its origin over perovskite oxides and paves a feasible pathway for rational design of high-performance catalysts in heterogeneous reactions.