Regulation of Active Oxygen Species by Grain Boundaries to Optimize Reaction Paths toward Aerobic Oxidations

Aerobic oxidation by using molecular oxygen (O-2) as the oxidant is highly attractive, in which activating O(2)to reactive oxygen species (ROS) is a prerequisite. Although some progress has been achieved in regulating ROS by heterogeneous catalysts, the strategies to efficiently control ROS in aerobic oxidation are still urgently desired. Herein, grain boundaries (GBs) in metal oxides are discovered to be able to facilely regulate ROS. Impressively, MoO(3)nanocrystals with high density of GBs (MoO3-600) deliver a mass activity of 83 mmol g(-1 )h(-1)in aerobic oxidation of benzyl alcohol, 7 and 8 times as high as that of MoO(3)nanoparticles without GBs and Pt/C, respectively. In addition, the selectivity of benzoic acid is 100% during whole reaction process over MoO3-600. Mechanistic studies reveal that the oxygen atoms at GBs in MoO3-600 are highly active to form center dot OH radicals with the generation of oxygen vacancies, while the oxygen vacancies are replenished by O-2. The reaction path directly contributes to the excellent catalytic performance.