AVS 47th International Symposium
    Surface Science Monday Sessions
       Session SS1-MoM

Paper SS1-MoM6
Surface Structure and Chemical Properties of a MnO/Rh(100) Model Catalyst

Monday, October 2, 2000, 10:00 am, Room 208

Session: Atomic-Scale Studies of Model Catalysts
Presenter: J. Nakamura, University of Tsukuba, Japan
Authors: J. Nakamura, University of Tsukuba, Japan
H. Nishimura, University of Tsukuba, Japan
J. Ogawa, University of Tsukuba, Japan
T. Fujitani, National Institute for Resources and Environment, Japan
Correspondent: Click to Email
The atomic structure of a MnO-deposited Rh(100) surface was studied using STM and LEED. The STM image of MnO/Rh(100) at a Mn coverage of 0.80 showed two hexagonal MnO domains rotated by 90 degree with respect to each other. One of the unit vectors for these hexagonal domains had same direction as the unit vector of the Rh(100) substrate. An averaged spacing of 0.31 nm was obtained by the STM for the nearest neighbor atoms of the hexagonal layer. The LEED pattern showed two hexagonal domains, which were consistent with the atomic structure observed by STM. The structure of hexagonal monolayer was very similar to MnO(111) in terms of lattice constant and symmetry. Adsorption of CO on the MnO/Rh(100) was studied using in-situ IRAS. Linear and bridge CO was observed on the clean Rh(100) and MnO/Rh(100) surfaces. New peaks or peak shifts were not observed on the MnO/Rh(100) in disagreement with the powder catalyst results of a Mn-promoted Rh catalyst. No IRAS peaks of CO were observed on the MnO/Rh(100) above the MnO coverage of unity, indicating that a monolayer MnO species grew on the Rh(100). The ratio of linear and bridged CO species varied with MnO coverage, suggesting that the surface area of bare Rh(100) planes on the MnO/Rh(100) controlled the ratio. The oxygen of MnO/Rh(100) is readily reacted with CO to form CO@sub 2@ at 300-400 K in UHV. The reaction probability at 373 K is close to unity.