| AVS 54th International Symposium | |
| Surface Science | Wednesday Sessions |
| Session SS2-WeA |
| Session: | Oxide Surface Structure I |
| Presenter: | J. Zhou, Oak Ridge National Laboratory |
| Authors: | J. Zhou, Oak Ridge National Laboratory A.P. Baddorf, Oak Ridge National Laboratory V. Meunier, Oak Ridge National Laboratory S.V. Kalinin, Oak Ridge National Laboratory S.H. Overbury, Oak Ridge National Laboratory D.R. Mullins, Oak Ridge National Laboratory |
| Correspondent: | Click to Email |
Cerium oxide and ceria-supported metal nanoparticles are important heterogeneous catalysts. They exhibit unique chemical reactivity dependent on Ce oxidation state as revealed by our previous XPS and TPD studies. To elucidate the nature of their reactivity, we investigated their structure and morphology using STM. Reducible (111) oriented thin films were grown in situ on Ru(0001) under ultrahigh vacuum conditions. Our data demonstrate that surface structures of ceria films are dependent on the film thickness and the degree of ceria reduction. Hexagonal superlattice structures consisting of five CeO2 unit cells coincident with seven Ru unit cells can be produced when the films are two or three layers thick and disappear with the increase of film thickness. DFT calculations were performed to explain the origin of these superlattice structures. Fully oxidized CeO2(111) film exhibits a fairly low density of point defects due to the formation of O vacancies. However, the number of surface defects increases as the ceria film is reduced. Metal particles (Pd and Rh) were vapor-deposited onto ceria thin films at 300 K. The growth of metal particles was investigated by STM as a function of metal coverage, post-deposition annealing temperatures, as well as Ce oxidation state. The research is sponsored by DOE BES Division of Chemical Sciences, Geosciences, and Biosciences.