Density functional study of benzene adsorption on the alpha-Mo2C(0001) surface

作者：Zhou Baojing; Liu Xingchen; Cuervo Javier; Salahub Dennis R^*

来源：Structural Chemistry, 2012, 23(5): 1459-1466.

DOI：10.1007/s11224-012-0064-5

Molybdenum carbide (Mo2C) is a valuable industrial catalyst for hydrogenation (HYD) of aromatic compounds-an essential step in in-situ heavy-oil upgrading. Despite the intensive studies on catalytic properties of molybdenum carbides, the basic mechanism of HYD reactions occurring on the surface of Mo2C remains vague. We studied the adsorption of benzene on an alpha-Mo2C(0001) surface at 0.25-mL coverage with first-principles density functional theory (DFT) calculations to provide further insight into the catalytic mechanism. Five high-symmetry adsorption sites combined with two different orientations of the aromatic ring parallel to the surface were investigated at the GGA-PBE level of DFT. Our results suggest that hollow sites are preferred over bridge sites. For the most favorable adsorption sites, i.e., Hc and Vc, the adsorption energy is ca. -2.5 eV. In addition, DFT-D2 calculations were carried out to incorporate the effect of dispersion. Consequently, the adsorption energies at various sites increased by ca. -1.3 eV in general, while the adsorption geometries were little affected. Analysis of the optimized adsorption geometries and the partial density of states revealed a strong interaction between the aromatic ring of benzene and the Mo2C surface, which leads to the rehybridization of benzene carbon atoms, from sp (2) to sp (3).

• 出版日期2012-10
• 单位南京理工大学