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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Quantitative Investigation of MgO Bronsted Basicity: DFT, IR, and Calorimetry Study of Methanol Adsorption
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Quantitative Investigation of MgO Bronsted Basicity: DFT, IR, and Calorimetry Study of Methanol Adsorption

机译：MgO布朗斯特碱的定量研究：DFT，IR和量热法研究甲醇吸附

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摘要

The adsorption geometries, energies, and vibrational frequencies of methanol on MgO defective surfaces have been calculated by periodic DFT simulations. The results are very comparable with those obtained with water and are also in very good accordance with microcalorimetry and infrared experiments. At low coverage, the dissociation is observed on all defects involving ions in low coordinations. Over and above the coordination number of surface ions, the adsorption energy is strongly governed by the surface topology: dissociation on confined sites gives rise to methoxy groups highly stabilized by bridging two or even three cations. The occurrence of such very strong sites on MgO powder is confirmed by microcalorimetry. The dissociation ability depends on the methanol coverage because it modifies the surface relaxation and the network of H bonds, resulting, for a given defect, in similar adsorption energies for molecular and dissociated species at high coverage. This explains why there are more strong sites (quantified by microcalorimetry) than dissociating sites (quantified by infrared).
机译：通过定期DFT模拟计算出了MgO缺陷表面上甲醇的吸附几何形状，能量和振动频率。结果与水获得的结果非常可比，并且与微量热法和红外实验也非常吻合。在低覆盖率下，在所有低配位离子中都观察到离解。除了表面离子的配位数以外，吸附能还受表面拓扑结构的支配：在受限位点的离解产生通过桥连两个或三个阳离子而高度稳定的甲氧基。通过微量量热法证实了在MgO粉末上存在这种非常强的位点。离解能力取决于甲醇的覆盖率，因为它改变了表面弛豫和氢键的网络，对于给定的缺陷，在高覆盖率下分子和离解物种的吸附能相似。这就解释了为什么比解离位点（通过红外量度）强的位置（通过量热法量化）要强。

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