| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Nanomaterials | Monday Sessions |
| Session NM-MoE |
| Session: | Nanomaterials Characterization & Reactivity I |
| Presenter: | Katsuyuki Fukutani, University of Tokyo, Japan |
| Authors: | S. Ohno, University of Tokyo, Japan S. Ogura, University of Tokyo, Japan M. Wilde, University of Tokyo, Japan K. Fukutani, University of Tokyo, Japan |
| Correspondent: | Click to Email |
Pd is a typical material that absorbs hydrogen in its bulk, and hydrogen absorbed in Pd clusters was shown to play an essential role in olefin hydrogenation reactions [1,2]. We have recently studied absorption of hydrogen in Pd(110) [3] and Pd70Au30(110) [4], and shown that hydrogen can be efficiently absorbed in Pd70Au30(110) [4]. In the present work, we have studied reactivity of Pd(110) and Pd70Au30(110) alloy surfaces towards olefin hydrogenation reactions with thermal desorption spectroscopy (TDS) and nuclear reaction analysis (NRA) that allows for high-resolution depth profiling of hydrogen [5].
When a Pd(110) surface was exposed to H2 at a low temperature, TDS revealed desorption features at ~150 K and ~300 K, which are attributed to hydrogen absorbed in the bulk and adsorbed on the surface, respectively [3]. Whereas coadsorption of C4H8 with surface H on Pd(110) revealed no hydrogenation reaction, hydrogenated products of C4H10 were clearly observed in presence of H in the absorbed state. When the Pd70Au30(110) surface was exposed to H2, on the other hand, a single desorption feature was recognized at ~250 K, which is different from both the pure Pd(110) and Au(110) surfaces [4]. Examination of the Pd70Au30(110) surface with low-energy electron diffraction and Auger electron spectroscopy revealed that Au segregates at the surface of the alloy. Hydrogen is dissociated at minor Pd sites on the surface and absorbed into bulk through the Pd site without spillover onto the Au site [4]. When C4H8 was adsorbed on the D-absorbed Pd70Au30(110) surface, TDS showed no hydrogenated products of C4H10, which is in remarkable contrast with the Pd(110) surface. Instead of the hydrogenation reaction, H-D exchange reactions were clearly observed. We discuss the reaction mechanisms on these two surfaces.
References
1) A. M. Doyle et al., Ang. Chem. Int. Ed. 42 (2003) 5240.
2) M. Wilde et al., Ang. Chem. Int. Ed. 47 (2008) 9289.
3) S. Ohno et al., J Chem. Phys. 140 (2014) 134705.
4) S. Ogura et al., J. Phys. Chem. C 117 (2013) 9366.
5) K. Fukutani, Curr. Opin. Sol. Stat. Mater. Sci. 6 (2002) 153.