Smith R Scott, Matthiesen Jesper, Kay Bruce D
Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
J Phys Chem A. 2014 Sep 18;118(37):8242-50. doi: 10.1021/jp501038z. Epub 2014 Apr 3.
The desorption kinetics of methanol, ethanol, and water from graphene covered Pt(111) are investigated. The temperature programmed desorption (TPD) spectra for both methanol and ethanol have well-resolved first, second, third, and multilayer layer desorption peaks. The alignment of the leading edges is consistent with zero-order desorption kinetics from all layers. In contrast, for water, the first and second layers are not resolved. At low water coverages (<1 monolayer (ML)) the initial desorption leading edges are aligned but then fall out of alignment at higher temperatures. For thicker water layers (10-100 ML), the desorption leading edges are in alignment throughout the desorption of the film. The coverage dependence of the desorption behavoir suggests that at low water coverages the nonalignment of the desorption leading edges is due to water dewetting from the graphene substrate. Kinetic simulations reveal that the experimental results are consistent with zero-order desorption. The simulations also show that fractional order desorption kinetics would be readily apparent in the experimental TPD spectra.
研究了甲醇、乙醇和水从石墨烯覆盖的Pt(111)上的脱附动力学。甲醇和乙醇的程序升温脱附(TPD)谱都有分辨率良好的第一、第二、第三和多层脱附峰。前沿的对齐与所有层的零级脱附动力学一致。相比之下，对于水，第一和第二层没有分辨出来。在低水覆盖率(<1单层(ML))时，初始脱附前沿是对齐的，但在较高温度下会失准。对于较厚的水层(10 - 100 ML)，脱附前沿在整个薄膜脱附过程中都是对齐的。脱附行为的覆盖率依赖性表明，在低水覆盖率下脱附前沿的不对齐是由于水从石墨烯基底上的去湿。动力学模拟表明实验结果与零级脱附一致。模拟还表明，分数级脱附动力学在实验TPD谱中很容易显现出来。
