Catalytic properties of trivalent rare-earth oxides with intrinsic surface oxygen vacancy

Oxygen vacancy (O_v) is an anionic defect widely existed in metal oxide lattice, as exemplified by CeO₂, TiO₂, and ZnO. As O_v can modify the band structure of solid, it improves the physicochemical properties such as the semiconducting performance and catalytic behaviours. We report here a new type of O_v as an intrinsic part of a perfect crystalline surface. Such non-defect O_v stems from the irregular hexagonal sawtooth-shaped structure in the (111) plane of trivalent rare earth oxides (RE₂O₃). The materials with such intrinsic O_v structure exhibit excellent performance in ammonia decomposition reaction with surface Ru active sites. Extremely high H₂ formation rate has been achieved at ~1 wt% of Ru loading over Sm₂O₃, Y₂O₃ and Gd₂O₃ surface, which is 1.5-20 times higher than reported values in the literature. The discovery of intrinsic O_v suggests great potentials of applying RE oxides in heterogeneous catalysis and surface chemistry.