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08월 28일 16시 이후 : 초록수정 불가능, 일정확인 및 검색만 가능
CO oxidation on Pt-group metal surfaces : particle size effects and metal-support interactions
2008년 8월 4일 20시 29분 03초
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금 10시 : 30분
Workshop on Surface and Interface Physical Chemistry
성균관대학교 화학과, Korea
Pt-group metals are widely used in heterogeenous catalysis. The atomic-scale mechanims of various reactions on Pt-group single crystal surfaces have been widely studied in surface chemistry; however, there are still many open questions regarding the surface structures of active catalysts. Recently, oxygen-rich phases on Ru, Pd and Pt surfaces were suggested to be catalytically extraordinarily active (which is referred to as "hyperactive surface"). Metallic surfaces with very hign oxygen coverages or thin metal oxide layers should be catalytically much more active than clean metal surfaces. The activity of real catalysts consisting of metal nanoparticles is often much different from those of the corresponding model catalysts, which are mostly metal single crystal ; as a function of particle size, catalytic activity can be significantly changed. In contrast to the Au catalysts, which shows enhanced catalytic activity with decreasing particle size, Pt nanoparticles show a lower reactivity than the Pt-bulk. We have recently carried out studies on CO oxidation reativities of various forms of Pt : CO oxidation on Pt-bulk, and Pt nanostructures on Ta-oxide and TiO2 were investigated. At the beginning of the reactivity measurements, Pt nanostructures on Ta-oxides are more reactive than the Pt-bulk; however, reactivity of Pt bulk is more greatly enhanced with increasing reaction time due to the formation of the hyperactive species, suggesting that the coverage effects should be considered in order to fully understand the size-dependence of the reactivity of Pt-catalysts. For Pt on TiO2, deactivation of Pt by strong metal-support interactions takes place. The deactivation of Pt could be avoided by the high-energy electron-beam treatment. The change of the TiO2 surface structure by the e-beam treatment will be discussed in detail, which is responsible for the inhibition of the deactivation of Pt-catalysts by TiO2.
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