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

Paper SS-TuP42
Adsorption Behavior and Reaction Properties of NO and CO on the Ir Surfaces

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

Session: Surface Science Poster Session
Presenter: I. Nakamura, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Authors: I. Nakamura, National Institute of Advanced Industrial Science and Technology (AIST), Japan
A. Takahashi, 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
T. Fujitani, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Correspondent: Click to Email
Selective catalytic reduction of NO in oxidizing atmospheres has recently received extensive attention, since it has potential as a practical measure to remove NOx emitted from diesel engines, lean-burn engines and combustors. A few studies of selective catalytic reduction of NO have been made with such reductants as H@sub 2@ and CO over the Ir-based catalysts. However, no evidence for explaining this reaction mechanism and the active site has been obtained. To clarify the role of CO for NO reduction, we studied the surface structure dependence for the reaction of NO and CO on the Ir single-crystal surfaces using surface science techniques such as XPS and IRAS. We examined the adsorption state of NO and CO on the Ir(111) and Ir(211) surfaces using IRAS. The peaks due to the adsorbed NO on hollow and atop sites were observed at 1400-1444 cm@super -1@ and 1799-1820 cm@super -1@ on Ir(111). On the other hand, the peaks due to the adsorbed NO on bridge and atop sites were observed at 1580-1590 cm@super -1@ and 1790-1810 cm@super -1@ on Ir(211), indicating that the NO adsorption was depended on the surface structure. Concerning the CO adsorption state, we observed the peak of CO adsorbed on atop site at 2060 cm@super -1@ over Ir(111) and at 2080 cm@super -1@ over Ir(211), indicating that the CO adsorption was not depended on the surface structure. We also investigated the thermal reactivity of the NO and CO adsorbed on the Ir(111) and Ir(211) surfaces. It was clearly demonstrated that the Ir step was active site for the NO dissociation. Furthermore, it was found that the NO reduction with CO on Ir surface proceeded via the direct decomposition of NO.