文献类型：期刊文献

英文题名：Effect of Ag on the control of Ni-catalyzed carbon formation: A density functional theory study

作者：Xu, Yue[1];Fan, Chen[1];Zhu, Yi-An[1];Li, Ping[1];Zhou, Xing-Gui[1];Chen, De[2];Yuan, Wei-Kang[1]

机构：[1]E China Univ Sci & Technol ECUST, State Key Lab Chem Engn, Shanghai 200237, Peoples R China;[2]Norwegian Univ Sci & Technol NTNU, Dept Chem Engn, N-7491 Trondheim, Norway

年份：2012

卷号：186

期号：1

起止页码：54

外文期刊名：CATALYSIS TODAY

收录：;EI(收录号：20122115058234);WOS:【SCI-EXPANDED(收录号:WOS:000304259800009)】；

基金：This research is supported by Natural Science Foundation of China (No. 21003046), 973 project of Ministry of Science and Technology of China (No. 2012CB720500), and Fundamental Research Funds for Central Universities (No. WA1014027). The computational time provided by the Notur project is highly acknowledged (nn4685k).

语种：英文

外文关键词：DFT; Coke resistance; Carbon nanofiber; Steam reforming; Ni; Ag

摘要：First-principles calculations have been performed to examine the effect of doped Ag on the kinetics of Ni-catalyzed methane dissociation and coke formation. The close-packed Ag/Ni(1 1 1) and stepped Ag/Ni(2 1 1) surfaces as well as the defect facets with step sites blocked by Ag or C atoms are constructed to investigate the role of the coordinatively unsaturated sites in the catalytic performance of Ni nanoparticles. The most stable CHx (x = 0-4) adsorption configurations and transition states for methane dissociation have been identified on both Ni and Ag/Ni surfaces. The calculated results indicate that the activation energy for methane dissociation is increased with the Ag coverage on Ni(1 1 1), and the C atoms deposited on the catalyst surface can be readily separated into small islands by Ag. On Ni(2 1 1) Ag atoms are predicted to bind preferentially to the middle-step sites which act as the nucleation center for the growth of filamentous carbon and therefore have the potential to prevent catalyst particles from being destroyed. Meanwhile, as the energy barrier for methane dissociation on the Ag-blocked Ni(2 1 1) surface is even higher than that on pure Ni(1 1 1), the active center is transferred from the stepped surface to the close-packed surface. These findings provide a rational interpretation of the experimental observations that Ag/Ni catalyst exhibits lower catalytic activity towards steam methane reforming but high resistance to coke deposition. (C) 2011 Elsevier B. V. All rights reserved.