Comparing the Catalytic Oxidation of Ethanol at the Solid鈥揋as and Solid鈥揕iquid Interfaces over Size-Controlled Pt Nanoparticles: Striking Differences in Kinetics and Mechanism
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- 作者：Andras Sapi ; Fudong Liu ; Xiaojun Cai ; Christopher M. Thompson ; Hailiang Wang ; Kwangjin An ; James M. Krier ; Gabor A. Somorjai
- 刊名：Nano Letters
- 出版年：2014
- 出版时间：November 12, 2014
- 年：2014
- 卷：14
- 期：11
- 页码：6727-6730
- 全文大小：279K
- ISSN：1530-6992
文摘
Pt nanoparticles with controlled size (2, 4, and 6 nm) are synthesized and tested in ethanol oxidation by molecular oxygen at 60 掳C to acetaldehyde and carbon dioxide both in the gas and liquid phases. The turnover frequency of the reaction is 鈭?0 times faster, and the activation energy is 鈭? times higher at the gas鈥搒olid interface compared to the liquid鈥搒olid interface. The catalytic activity is highly dependent on the size of the Pt nanoparticles; however, the selectivity is not size sensitive. Acetaldehyde is the main product in both media, while twice as much carbon dioxide was observed in the gas phase compared to the liquid phase. Added water boosts the reaction in the liquid phase; however, it acts as an inhibitor in the gas phase. The more water vapor was added, the more carbon dioxide was formed in the gas phase, while the selectivity was not affected by the concentration of the water in the liquid phase. The differences in the reaction kinetics of the solid鈥揼as and solid鈥搇iquid interfaces can be attributed to the molecular orientation deviation of the ethanol molecules on the Pt surface in the gas and liquid phases as evidenced by sum frequency generation vibrational spectroscopy.