Revealing the Atomic Surface Structures of CeO2 Nanocrystals via
Significance and Impact:
The HREM images show the atomic surface structures of different facets.
Atomic surface structures of CeO2 are of particular interest in chemical and electrochemical catalysis. The previous surface studies on CeO2 are either not on nanoparticles or incapable of “seeing” the O atoms. As a result, the conclusions are often contradictory. In this work, we determined the (100), (110) and (111) surfaces of CeO2 nanocubes at atomic resolution including the O atoms using aberration corrected high resolution electron microscopy. For the predominantly exposed high energy (100) surface, we directly observed the presence of Ce, O and reduced CeO terminations on the outermost surface as well as the partially occupied atoms in the near-surface region (~1 nm from the surface). The previously often assumed CeO termination of the (100) surface is oversimplified. For the (110) surface, there is a combination of reduced flat CeO2-x outermost surface layers and “saw-like” (111) nanofacets. For the (111), the surface is O layer terminated. Furthermore, all the surface results derived from the HREM study are consistent with our infrared spectroscopy study.
Surface Chemistry and Catalysis R&D Projects