AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP43
Reactions of SO@sub 2@ and Between Atomic S and O@sub 2@ on the Ir(111) and Rh(111) Surfaces

Tuesday, November 14, 2006, 6:00 pm, Room 3rd Floor Lobby

Session: Surface Science Poster Session
Presenter: T. Fujitani, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Authors: T. Fujitani, National Institute of Advanced Industrial Science and Technology (AIST), Japan
I. Nakamura, National Institute of Advanced Industrial Science and Technology (AIST), Japan
M. Haneda, National Institute of Advanced Industrial Science and Technology (AIST), Japan
H. Hamada, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Correspondent: Click to Email
It has been reported that Ir/SiO@sub 2@ shows marked catalytic activity for NO reduction with CO in the presence of O@sub 2@ and SO@sub 2@. However, no evidence was obtained for the role of SO@sub 2@. We examined the role of SO@sub 2@ for NO reduction with CO in the presence O@sub 2@. The reactions of SO@sub 2@ on Ir(111) and Rh(111) were investigated using XPS. On Ir(111), the peaks due to molecularly adsorbed SO@sub 2@ were observed after SO@sub 2@ exposure at 200 K. With the rise of temperature at 300 K, two S 2p peaks were observed at 165.9 and 162.4 eV. The peak at 162.4 eV was assigned to atomic S. The ratio of coverage of S 2p (165.9 eV) and O 1s (530.7 eV) was almost 3, indicating that these peaks corresponded to the SO@sub 3@. After annealing to 400 K, the adsorbed SO@sub 3@ significantly decreased and the atomic oxygen was observed. The SO@sub 3@ and atomic oxygen were completely desorbed and the only atomic S was presented on the surface above 500 K. On Rh(111), SO@sub 2@ was molecularly adsorbed on the surface at 200 K. The adsorbed SO@sub 2@ dissociated to atomic S and oxygen above 300 K. The only atomic S was presented on both surfaces above 500 K, but the formation process of atomic S on Ir(111) was different from that on Rh(111). The reaction between atomic S and O@sub 2@ was examined on Ir(111) and Rh(111). On Ir(111), S coverage decreased with increasing O@sub 2@ exposure at 500 K, and then no atomic S was observed at 1000 s, indicating that atomic S reacted with surface oxygen and was removed from the surface in the presence of oxygen. In contrast, S coverage was almost constant on Rh(111). Thus, the reactivity of atomic S with oxygen on Ir(111) was significantly higher than that on Rh(111).