Fig. 1: Atomic structures of planar CeO2(111) and well-defined ceria clusters.
From: Dynamic control and quantification of active sites on ceria for CO activation and hydrogenation
a Large-scale STM image of the CeO2(111) film surface. b O-mode STM image of the CeO2(111) surface. The squared area is magnified in (c), showing surface O vacancy (Vsur-O) as a dark hole and sub-surface O vacancy (Vsub-O) as a three-pointed depression star at the hollow site of O atoms. The CeO2(111) surface is dominated by Vsub-O. d The corresponding structural model of O vacancies. Ce atoms, surface, and subsurface O atoms are displayed in white, red, and blue, respectively. e Atomic-resolution STM images (upper panel, scale bar: 1 nm) and the corresponding structural models of supported Ce3O3, Ce3O7, Ce6O13, Ce10O21, and Ce15O31 clusters (lower panel). DFT-optimized structural models of Ce3O3 supported on Ce2O3(0001) and Ce3O7 supported on CeO2(111) are displayed with labels on their O-coordination numbers of Ce sites. Surface lattice parameters are close for Ce2O3(0001) and CeO2(111), which exhibited major differences in stacking along the vertical direction. OU, OL, and OC represent O atoms in the topmost O layer, the lower O layer, and supported CeOx clusters, respectively.
