Bolina Amandeep S, Wolff Angela J, Brown Wendy A
Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, U.K.
J Phys Chem B. 2005 Sep 8;109(35):16836-45. doi: 10.1021/jp0528111.
Reflection absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) have been used to perform a detailed investigation of the adsorption of water on highly oriented pyrolytic graphite (HOPG) at 90 K. RAIRS shows that water is physisorbed on HOPG at all coverages, as expected. Experiments at higher surface temperatures show marked changes in the O-H stretching region of the spectrum which can be assigned to the observation of the amorphous to crystalline ice phase transition. The infrared signature of both phases of solid water has been determined on HOPG and can be used to identify the phase of the ice. TPD spectra show the desorption of multilayers of crystalline ice. At high exposures a small bump appears in the TPD spectrum, on the low temperature side of the main peak, which is attributed to the amorphous to crystalline phase transition. At very low exposures of water, it is possible to distinguish the desorption of water from two- and three-dimensional islands and hence to determine the growth mode of water on the HOPG surface. Isothermal TPD studies have also been performed and show that the desorption of water does not obey perfect zero-order kinetics. Desorption orders, derived directly from the TPD spectra, confirm this observation. Desorption energies and preexponential factors have also been determined for this adsorption system.
反射吸收红外光谱（RAIRS）和程序升温脱附（TPD）已被用于详细研究90K下高度取向热解石墨（HOPG）表面水的吸附情况。正如预期的那样，RAIRS表明在所有覆盖度下，水均以物理吸附的方式吸附在HOPG上。在较高表面温度下进行的实验表明，光谱的O-H伸缩区域出现了显著变化，这可归因于非晶态到晶态冰的相变观测。已在HOPG上确定了固态水两个相的红外特征，可用于识别冰的相态。TPD光谱显示了多层晶态冰的脱附。在高暴露量下，TPD光谱主峰低温侧出现一个小凸起，这归因于非晶态到晶态的相变。在水的暴露量非常低时，可以区分二维和三维岛状结构上的水的脱附，从而确定水在HOPG表面的生长模式。还进行了等温TPD研究，结果表明水的脱附并不遵循完美的零级动力学。直接从TPD光谱得出的脱附级数证实了这一观察结果。还确定了该吸附体系的脱附能和指前因子。
