Ni/Pt(111) Bimetallic Surfaces: Unique Chemistry at Monolayer Ni Coverage
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- 作者：Henry H. Hwu ; Joseph Eng ; Jr. ; and Jingguang G. Chen
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：January 30, 2002
- 年：2002
- 卷：124
- 期：4
- 页码：702 - 709
- 全文大小：136K
- 年卷期：v.124,no.4(January 30, 2002)
- ISSN：1520-5126
文摘
We have utilized the dehydrogenation and hydrogenation of cyclohexene as probe reactions tocompare the chemical reactivity of Ni overlayers that are grown epitaxially on a Pt(111) surface. The reactionpathways of cyclohexene were investigated using temperature-programmed desorption, high-resolutionelectron energy loss (HREELS), and near edge X-ray absorption fine structure (NEXAFS) spectroscopy.Our results provide conclusive spectroscopic evidence that the adsorption and subsequent reactions ofcyclohexene are unique on the monolayer Ni surface as compared to those on the clean Pt(111) surfaceor the thick Ni(111) film. HREELS and NEXAFS studies show that cyclohexene is weakly 
-bonded onmonolayer Ni/Pt(111) but di-
-bonded to Pt(111) and Ni(111). In addition, a new hydrogenation pathwayis detected on the monolayer Ni surface at temperatures as low as 245 K. By exposing the monolayerNi/Pt(111) surface to D2 prior to the adsorption of cyclohexene, the total yield of the normal and deuteratedcyclohexanes increases by approximately 5-fold. Furthermore, the reaction pathway for the completedecomposition of cyclohexene to atomic carbon and hydrogen, which has a selectivity of 69% on the thickNi(111) film, is nearly negligible (<2%) on the monolayer Ni surface. Overall, the unique chemistry of themonolayer Ni/Pt(111) surface can be explained by the weaker interaction between adsorbates and themonolayer Ni film. These results also point out the possibility of manipulating the chemical properties ofmetals by controlling the overlayer thickness.
-bonded onmonolayer Ni/Pt(111) but di--bonded to Pt(111) and Ni(111). In addition, a new hydrogenation pathwayis detected on the monolayer Ni surface at temperatures as low as 245 K. By exposing the monolayerNi/Pt(111) surface to D2 prior to the adsorption of cyclohexene, the total yield of the normal and deuteratedcyclohexanes increases by approximately 5-fold. Furthermore, the reaction pathway for the completedecomposition of cyclohexene to atomic carbon and hydrogen, which has a selectivity of 69% on the thickNi(111) film, is nearly negligible (<2%) on the monolayer Ni surface. Overall, the unique chemistry of themonolayer Ni/Pt(111) surface can be explained by the weaker interaction between adsorbates and themonolayer Ni film. These results also point out the possibility of manipulating the chemical properties ofmetals by controlling the overlayer thickness.