A Theoretical Study of Catalytic Coupling of Propyne on Cu{111}
A Theoretical Study of Catalytic Coupling of Propyne on Cu{111}
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丙炔与 Cu{111} 催化偶联的理论研究
DOI：
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发表时间：
2000
期刊：
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通讯作者：
R. M. Lambert
中科院分区：
文献类型：
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作者：
A. Clotet;J. Ricart;F. Illas;G. Pacchioni;R. M. Lambert
用密度泛函集团模型方法研究了丙炔分子在Cu{111}表面的耦合机理。气相二聚是非常不利的，因为通过促进分子到三重态来活化丙炔的能量成本。然而，在表面上，丙炔以非常接近于处于三重态的气相丙炔的几何形状被吸附，因此，反应分子的活化不会引起任何额外的能量消耗。此外，异构化为乙烯基卡宾是必要的，以允许头-尾或头-头偶联，产生1，4-和1，3-环己二烯中间体。乙烯基卡宾双自由基存在于表面，因为异构化过程几乎没有（热力学）成本。实验表明，头对头和头对头的相互作用都是可能的。这两种环己二烯中间体都可以以适度的能量成本重结晶以产生苯和H2。另一种头对头的互动，没有int.
The coupling mechanism of two propyne molecules on the Cu{111} surface has been studied by means of a DFT cluster model approach. The gas-phase dimerization is highly unfavored because of the energy cost to activate propyne by promoting molecules to the triplet state. However, on the surface, propyne is adsorbed with a geometry very close to that of gas-phase propyne in the triplet state and, therefore, activation of the reacting molecules does not incur any additional energy cost. Moreover, isomerization to vinylcarbene is necessary to allow head-to-tail or head-to-head coupling resulting in 1,4- and 1,3-cyclohexadiene intermediates. Vinylcarbene biradicals are present at the surface because the isomerization process proceeds at practically no (thermodynamic) cost. Both head-to-tail and head-to-head interactions suggested by experiment are possible. Both cyclohexadiene intermediates can dehydrogenate to yield benzene and H2 with a moderate energy cost. An alternative head-to-head interaction, without int...