摘要
用DV—X_α方法对铁石墨嵌合物及乙炔、乙烯在其上的吸附行为进行了研究。计算结果表明,铁石墨嵌合物的生成不仅引起了催化位铁几何排列的变化,而且改变了铁的电子性质。乙炔在吸附过程中能通过π→d,d→π~*相互作用,有效地削弱C—Cπ键,有利于进行加氢还原。乙烯不能通过这种机理被铁石墨嵌合物有效地活化。在此基础上,讨论了铁石墨嵌合物电极对乙炔的电催化还原作用,认为乙炔以负离子形式,缔合式吸附在电极表面,直接在电极上还原为乙烯。
The adsorption behavior of acetylene, ethylene on Fe-Graphite Intercalation Compounds (FEGIC) has been studied by DV-Xα method. Based on the experiments, Fe/C6H6 (Fe-C8H6 2.50A°;C-C,C-H 1.42A°) is proposed as a calculation model of FEGIC, and acetylene, ethylene will be adsorbed on single Fe atom of FEGIC. The calculation results show that: (1)The formation of FEGIC not only changes the geometry of adsorbed sites, but also changes the electronic properties of the intercalated metal atoms. (2) The frontier orbits of FEGIC are a pair of singly-occupied degenerated 3d orbits of iron, which play an important role in the adsorption. By the interaction of π→d, d→π, C-Cπ bond of acetylene is weakened efficiently, which makes the reduction of acetylene easy to occur. For lack of such a pair of π, π orbits of suitable symmetry, ethylene cannot be activated by FEGIC. (3) As concerns the electro-catalytic reduction of acetylene, the FEGIC electrode is more active than the pure graphite electrode; negative acetylene is adsorbed associatively on the surface of the FEGIC electrode, undergoing direct reduction (H++e) to form ethylene selectively.
基金
国家自然科学基金
