Infrared Activities of Adsorbed Species on Metal Surfaces: The Puzzle of Adsorbed Methyl (CH 3 )
Infrared Activities of Adsorbed Species on Metal Surfaces: The Puzzle of Adsorbed Methyl (CH 3 )
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金属表面吸附物质的红外活动：吸附甲基 (CH 3 ) 之谜
DOI：
10.1021/acs.jpclett.1c03342
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Jiang, Bin
中科院分区：
文献类型：
--
作者：
Zhou, Xueyao;Vejayan, Harmina;Beck, Rainer D.;Guo, Hua;Jiang, Bin
反射-吸收红外光谱（RAIRS）被广泛用于在表面化学反应过程中识别金属上的分子吸附物，但仅凭实验很难解释RAIRS数据。在这里，我们揭示了从第一性原理计算的对比RAIRS光谱的甲基吸附在Pt（111）和Ni（111）的起源。我们发现，在Pt（111）上，CH_3分子沿表面法线的对称C-H伸缩振动所产生的动力学偶极是显著的，而在Ni（111）上则很小，可以忽略不计，这解释了前者的强IR活性和后者的RAIRS峰的缺失.这种差异与金属和吸附质之间的不同电荷转移模式有关，这是由甲基在两个表面上的不同优选吸附位点决定的。这项工作突出了需要的电子结构计算在解释RAIRS光谱的吸附在金属表面上。
Reflection–absorption infrared spectroscopy (RAIRS) is widely used to identify molecular adsorbates on metals during surface chemical reactions, but the interpretation of RAIRS data can be difficult with experiment alone. Here, we reveal from first-principles calculations the origin of the contrasting RAIRS spectra of methyl adsorbed on Pt(111) and Ni(111). We find that the dynamic dipole associated with the symmetric C–H stretch vibration of CH3along surface normal is significant on Pt(111) but negligibly small on Ni(111), explaining the strong IR activity in the former and the absence of any RAIRS peaks in the latter. This difference is correlated to different charge transfer patterns between metals and the adsorbate, which are determined by the different preferred adsorption sites of methyl on the two surfaces. This work highlights the need of electronic structure calculations in interpreting RAIRS spectra of adsorbates on metal surfaces.