配体保护下的Au_(20)团簇吸附和活化CO的理论研究
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摘要
用密度泛函理论方法计算了CO分子吸附在有机配体聚乙烯吡咯烷酮poly(N-vinyl-2-pyrrolidone)(PVP)保护下的Au20团簇上的稳定构型的结构和性质。配体PVP通过物理吸附主要作用于Au20团簇的顶点位置。与Au20比较,配体的存在有利于CO的吸附和活化,其根本原因是PVP和CO在Au20表面分别作为供电子和吸电子基团产生的协同效应。中性及阴离子Au20团簇对配体和CO的吸附强度不同,前者对PVP吸附作用较强,后者对CO的吸附和活化作用较强。
The geometrical and electronic structures of low-lying isomers of CO adsorbed Au20 clusters protected by poly( N-vinyl-2-pyrrolidone)( PVP) were investigated using density functional theory calculations. PVP mainly occupies the apex of Au20 clusters via a physisorption pattern. Compared to the bare Au20 cluster,Au20: PVP has higher activity towards CO,resulting from the co-adsorption effect that PVP serves as an electron donor and CO as an electron acceptor on the cluster surface. The neutral and anionic Au20 clusters exhibit different adsorption behaviors towards PVP and CO. The neutral prefers PVP,while the anion prefers CO.
The geometrical and electronic structures of low-lying isomers of CO adsorbed Au20 clusters protected by poly( N-vinyl-2-pyrrolidone)( PVP) were investigated using density functional theory calculations. PVP mainly occupies the apex of Au20 clusters via a physisorption pattern. Compared to the bare Au20 cluster,Au20: PVP has higher activity towards CO,resulting from the co-adsorption effect that PVP serves as an electron donor and CO as an electron acceptor on the cluster surface. The neutral and anionic Au20 clusters exhibit different adsorption behaviors towards PVP and CO. The neutral prefers PVP,while the anion prefers CO.
引文
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[2]Lemire C,Meyer R,Shaikhutdinov S,et al.Do Quantum Size Effects Control CO Adsorption on Gold Nanoparticles[J].J Angew Chem Int Ed,2004,43(1):118-121.
[3]Okumura M,Kitagawa,Y,Yamaguchi K,et al.Direct Production of Hydrogen Peroxide from H2and O2over Highly Dispersed Au catalysts[J].Chem Lett,2003.32(9):822-823.
[4]Hayashi T,Tanaka K,Haruta M.Selective Vapor-Phase Epoxidation of Propylene over Au/Ti O2Catalysts in the Presence of Oxygen and Hydrogen[J].J Catal,1998,178(2):566-575.
[5]Tsunoyama H,Ichikuni N,Sakurai H,et al.Effect of Electronic Structures of Au Clusters Stabilized by Poly(N-vinyl-2-pyrrolidone)on Aerobic Oxidation Catalysis[J].J Am Chem Soc,2009,131(20):7086-7093.
[6]Tsunoyama H,Ichikuni N,Sakurai H,et al.Effect of Electronic Structures of Au Clusters Stabilized by Poly(N-vinyl-2-pyrrolidone)on Aerobic Oxidation Catalysis[J].J Am Chem Soc,2009,131(20):7086-7093.
[7]Perdew J P,Burke K,Ernzerhof M.Generalized gradient approximation made simple[J].Phys Rev Lett,1996.77(18):3865-3868.
[8]Becke A D.Density-functional exchange-energy approximation with correct asymptotic behavior[J].Phys Rev A,1988,38(6):3098-3100.
[9]Lee C L,Yang W,Parr R G.Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density[J].Phys Rev B,1988,37:785-789.
[10]Tao J M,Perdew J P,Staroverov V N,et al.Climbing the Density Functional Ladder:Nonempirical Meta-Generalized Gradient Approximation Designed for Molecules and Solids[J].Phys Rev Lett,2003,91(14):146401-146404.
[11]Wood J H,Boring A M,Improved Pauli Hamiltonian for local-potential problems[J].Phy Rev B,1978,18(6):2701-2706.
[12]Andrae D,Haeussermann U,Dolg M,et al.Energy-adjusted ab Initio pseudopotentials for the second and third row transition elements[J].Theor Chim Acta,1990,77:123-141.
[13]TURBOMOLE V5-9-1.University of Karlsruhe 2007.
[14]Jang N D,Kohn W.Theory of metal surfaces:work function[J].Phys Rev B,197l,3(4):1215-1223.
[15]Geerlings P,De Proft F,Langenaeker W.Conceptual Density Functional Theory[J].Chem Rev,197l,103(5):1793-1873.