Bratlie Kaitlin M, Lee Hyunjoo, Komvopoulos Kyriakos, Yang Peidong, Somorjai Gabor A
Department of Chemistry, University of California, Berkeley, California 94720, USA.
Nano Lett. 2007 Oct;7(10):3097-101. doi: 10.1021/nl0716000. Epub 2007 Sep 18.
Benzene hydrogenation was investigated in the presence of a surface monolayer consisting of Pt nanoparticles of different shapes (cubic and cuboctahedral) and tetradecyltrimethylammonium bromide (TTAB). Infrared spectroscopy indicated that TTAB binds to the Pt surface through a weak C-H...Pt bond of the alkyl chain. The catalytic selectivity was found to be strongly affected by the nanoparticle shape. Both cyclohexane and cyclohexene product molecules were formed on cuboctahedral nanoparticles, whereas only cyclohexane was produced on cubic nanoparticles. These results are the same as the product selectivities obtained on Pt(111) and Pt(100) single crystals in earlier studies. The apparent activation energy for cyclohexane production on cubic nanoparticles is 10.9 +/- 0.4 kcal/mol, while for cuboctahedral nanoparticles, the apparent activation energies for cyclohexane and cyclohexene production are 8.3 +/- 0.2 and 12.2 +/- 0.4 kcal/mol, respectively. These activation energies are lower, and corresponding turnover rates are three times higher than those obtained with single-crystal Pt surfaces.
在由不同形状（立方体形和立方八面体形）的铂纳米颗粒和十四烷基三甲基溴化铵（TTAB）组成的表面单层存在下，对苯加氢反应进行了研究。红外光谱表明，TTAB通过烷基链的弱C-H...Pt键与铂表面结合。发现催化选择性受纳米颗粒形状的强烈影响。立方八面体纳米颗粒上形成了环己烷和环己烯产物分子，而立方纳米颗粒上仅产生环己烷。这些结果与早期研究中在Pt(111)和Pt(100)单晶上获得的产物选择性相同。立方纳米颗粒上环己烷生成的表观活化能为10.9±0.4 kcal/mol，而对于立方八面体纳米颗粒，环己烷和环己烯生成的表观活化能分别为8.3±0.2和12.2±0.4 kcal/mol。这些活化能更低，相应的周转速率比单晶铂表面获得的周转速率高两倍。
