Formation and bonding of alane clusters on Al(111) surfaces studied by infrared absorption spectroscopy and theoretical modeling.
Formation and bonding of alane clusters on Al(111) surfaces studied by infrared absorption spectroscopy and theoretical modeling.
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通过红外吸收光谱和理论建模研究 Al(111) 表面上铝烷簇的形成和成键。
DOI：
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发表时间：
2008
影响因子：
15
通讯作者：
Y. Chabal
中科院分区：
文献类型：
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作者：
S. Chaudhuri;S. Rangan;J. Veyan;J. Muckerman;Y. Chabal
铝烷被认为是许多储氢反应中的质量传递中间体，因此对于理解铝烷酸盐和AlH 3的再氢化动力学是重要的。结合密度泛函理论（DFT）和表面红外（IR）光谱，我们提供了铝（111）表面，再氢化反应的模型环境的形成铝烷的原子细节。在低覆盖度下，DFT预测了原子氢在1150 cm（-1）处的2倍桥位吸附，该吸附太弱而无法通过IR检测到，但先前在电子能量损失光谱中观察到。在较高的覆盖率，步骤是最有利的原子H吸附的吸附位点，它是可能的，AlH 3分子的形式（最初强烈结合步骤）在饱和。随着曝光量的增加，从台阶边缘提取AlH 3，并成为高度移动的在弱结合状态的梯田，占在以前的STM研究中观察到的台阶蚀刻。这些弱结合的AlH 3分子的流动性是导致通过AlH 3齐聚生长较大铝烷的关键因素。随后的铝烷的分解和解吸也进行了研究，并与以前的程序升温解吸研究。
Alanes are believed to be the mass transport intermediate in many hydrogen storage reactions and thus important for understanding rehydrogenation kinetics for alanates and AlH3. Combining density functional theory (DFT) and surface infrared (IR) spectroscopy, we provide atomistic details about the formation of alanes on the Al(111) surface, a model environment for the rehydrogenation reactions. At low coverage, DFT predicts a 2-fold bridge site adsorption for atomic hydrogen at 1150 cm(-1), which is too weak to be detected by IR but was previously observed in electron energy loss spectroscopy. At higher coverage, steps are the most favorable adsorption sites for atomic H adsorption, and it is likely that the AlH3 molecules form (initially strongly bound to steps) at saturation. With increasing exposures AlH3 is extracted from the step edge and becomes highly mobile on the terraces in a weakly bound state, accounting for step etching observed in previous STM studies. The mobility of these weakly bound AlH3 molecules is the key factor leading to the growth of larger alanes through AlH3 oligomerization. The subsequent decomposition and desorption of alanes is also investigated and compared to previous temperature programmed desorption studies.