title: Mechanistic Insights into Ethylene Transformations on Ir(111) by Density Functional Calculations and Microkinetic Modeling.
abstract: Ethylidyne, ethane, and carbon monomer formations from ethylene over Ir(111) at different coverages are investigated using density functional theory methods. Two possible reaction mechanisms for ethylidyne formation are investigated. The calculations show that vinyl prefers the dehydrogenation to yield vinylidene (M2) over the hydrogenation to produce ethylidene (M1) kinetically and thermodynamically at 1/9 (1/3) ML. Ethylidyne formation could be a competitive side reaction of ethylene hydrogenation, however, the ethylidyne species does not directly participate in the ethylene hydrogenation mechanism. The mechanism for C monomer formation is also studied. Microkinetic modeling shows that the ethylene hydrogenation reactivity decreases in the sequence Ir(111)>Rh(111)>Pd(111)>Pt(111) under typical hydrogenation conditions. The catalytic activity of ethylene hydrogenation decreases with increased stability of ethylene adsorption and reaction barrier of the rate-limiting step.
authors.affiliation: College of Materials Engineering, Shanghai University of Engineering Science, Shanghai, 201620, P.R. China.|Institute of Physical Chemistry, University of Innsbruck, Innrain 80-82, Innsbruck, Austria.
authors.forename: Xue-Rong
authors.initials: XR
authors.lastname: Shi
authors.affiliation: College of Materials Engineering, Shanghai University of Engineering Science, Shanghai, 201620, P.R. China.
authors.forename: Haijuan
authors.initials: H
authors.lastname: Kong
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, 77204-4004, USA.
authors.forename: Shengguang
authors.initials: S
authors.lastname: Wang
authors.affiliation: Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, P.R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi, 030001, P. R. China.
authors.forename: Zhangfeng
authors.initials: Z
authors.lastname: Qin
authors.affiliation: State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi, 030001, P. R. China.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Wang
keywords: Ir(111); carbon monomers; density functional theory; ethylene; microkinetic modeling