Vinyl acetate （VA） synthesis on Pd/Au（111） and Pd/Au（100） surfaces has been systematically investigated through first-principles density functional theory （DFT） calculations. The DFr results showed that for VA...Vinyl acetate （VA） synthesis on Pd/Au（111） and Pd/Au（100） surfaces has been systematically investigated through first-principles density functional theory （DFT） calculations. The DFr results showed that for VA synthesis, the ＇Samanos＇ reaction mechanism （i.e., direct coupling of coadsorbed ethylene and acetate species and subsequent/%hydride elimination to form VA） is more favorable than the ＇Moiseev＇ mechanism （i.e., ethylene first dehydrogenates to form vinyl species which then couple with the coadsorbed acetate species to form VA）. More importantly, it was found the surface coverage of acetate has a significant effect on the reactivity of VA synthesis, and the activation energy of the rate- controlling step on Pd/Au（100） surface is smaller than that on Pd/Au（111） surface （0.88 vs. 0.95 eV）, indicating the former is more active than the latter.展开更多
采用密度泛函理论研究了M(M=In,Ir)原子修饰的M-Au(111)合金表面的稳定性,并选其最优模型探讨了合金表面的活性及其对巴豆醛的吸附。合金的几何构型、形成能和结合能等性质表明,In-Au(111)面的稳定性随In原子的间距增大而提高,Ir-Au(111...采用密度泛函理论研究了M(M=In,Ir)原子修饰的M-Au(111)合金表面的稳定性,并选其最优模型探讨了合金表面的活性及其对巴豆醛的吸附。合金的几何构型、形成能和结合能等性质表明,In-Au(111)面的稳定性随In原子的间距增大而提高,Ir-Au(111)面的稳定性随Ir原子的间距增大而降低。对于巴豆醛在MAu(111)面上的吸附,当其通过C=O吸附于合金表面的TopM位时,吸附能最大,吸附构型最稳定。从巴豆醛的结构变化、态密度、差分电荷密度以及Mulliken电荷布居等分析可以看出,稳定吸附构型的巴豆醛分子形变较大,电荷转移明显。其中,位于-7.04 e V至费米能级处的p、d轨道杂化,对体系的吸附具有重要贡献。分析比较In-Au(111)面与Ir-Au(111)面,发现后者的配体效应更佳,不仅具有更高的稳定性和活性,而且对于巴豆醛具有更强的吸附力。此外,相比于改性前的Au(111)面,M原子的修饰明显提升了金属表面的稳定性及吸附能力。展开更多
基金supported by the National Natural Science Foundation of China(21106094,21276179)National Key Basic Research Program of China(973)(2012CB720300)Program for Changjiang Scholars,Innovative Research Team in University,China(IRT1161)~~
基金supported by the State Key Program of Natural Science of Tianjin (Grant No. 13JCZDJC26800)the foundation of State Key Laboratory of Coal Conversion (Grant No. J13-14-908)
文摘Vinyl acetate （VA） synthesis on Pd/Au（111） and Pd/Au（100） surfaces has been systematically investigated through first-principles density functional theory （DFT） calculations. The DFr results showed that for VA synthesis, the ＇Samanos＇ reaction mechanism （i.e., direct coupling of coadsorbed ethylene and acetate species and subsequent/%hydride elimination to form VA） is more favorable than the ＇Moiseev＇ mechanism （i.e., ethylene first dehydrogenates to form vinyl species which then couple with the coadsorbed acetate species to form VA）. More importantly, it was found the surface coverage of acetate has a significant effect on the reactivity of VA synthesis, and the activation energy of the rate- controlling step on Pd/Au（100） surface is smaller than that on Pd/Au（111） surface （0.88 vs. 0.95 eV）, indicating the former is more active than the latter.
文摘采用密度泛函理论研究了M(M=In,Ir)原子修饰的M-Au(111)合金表面的稳定性,并选其最优模型探讨了合金表面的活性及其对巴豆醛的吸附。合金的几何构型、形成能和结合能等性质表明,In-Au(111)面的稳定性随In原子的间距增大而提高,Ir-Au(111)面的稳定性随Ir原子的间距增大而降低。对于巴豆醛在MAu(111)面上的吸附,当其通过C=O吸附于合金表面的TopM位时,吸附能最大,吸附构型最稳定。从巴豆醛的结构变化、态密度、差分电荷密度以及Mulliken电荷布居等分析可以看出,稳定吸附构型的巴豆醛分子形变较大,电荷转移明显。其中,位于-7.04 e V至费米能级处的p、d轨道杂化,对体系的吸附具有重要贡献。分析比较In-Au(111)面与Ir-Au(111)面,发现后者的配体效应更佳,不仅具有更高的稳定性和活性,而且对于巴豆醛具有更强的吸附力。此外,相比于改性前的Au(111)面,M原子的修饰明显提升了金属表面的稳定性及吸附能力。
