密度泛函理论研究CO、CO＋H在Ni(111)表面的吸附  

Density Functional Theory Study of CO,CO + H Adsorption on Ni(111) Surface

作　　者：桂岚岚 彭亮[1] 彭导灵[1] 顾凤龙[1] 

机构地区：[1]华南师范大学化学与环境学院,环境理论化学教育部重点实验室,广州510006

出　　处：《华南师范大学学报（自然科学版）》2016年第1期67-73,共7页Journal of South China Normal University(Natural Science Edition)

基　　金：国家自然科学基金项目(21273081)

摘　　要：采用密度泛函理论(DFT)研究了CO以及CO+H体系在金属Ni(111)表面的吸附行为.采用二维平板周期性结构模型来模拟金属Ni(111)表面,消除了团簇结构模型不能考虑体系边界效应的影响,更接近于真实金属表面.对CO在Ni(111)表面的吸附过程进行探究,结果表明:CO在不同的表面活性位吸附后C—O键不同程度被削弱;通过对吸附能以及吸附后C—O键长和C—O伸缩振动频率分析,发现顶位(top)、桥位(bridge)、六方密堆积三重穴位(hcp)和面心立方三重穴位(fcc)都以C端靠近表面的垂直吸附为稳定状态,均为非解离吸附,其中fcc与hcp两空穴位吸附性质几乎相同,为CO的最佳活性位.研究CO与氢(H)在Ni(111)表面的吸附过程的结果表明:部分CO通过双基端加H生成中间物种—OCH和—COH,C—O键很大程度被削弱,较不加H吸附时的C—O键更容易在活性位断裂,因而以金属Ni(111)表面做催化剂的情况下H的加入有助于CO的解离.A density functional theory （DFT） study of CO, CO ＋ H adsorption processes on Ni（ 111 ） surface is re- ported in this article. A two-dimensional periodic slab structure model is employed to simulate the Ni （ 111 ） surface and to eliminate the influence of the cluster model on system boundary effects, making the model closer to the true metal surface. This article is divided into two parts. The adsorption process of CO on Ni （ 111 ） surface is studied first, and the results showed that the C--O bonds are weakened in different surface active adsorption sites. Accord- ing to the analysis of adsorption energies, C--O bond lengths and the C--O stretching vibration frequencies, it is found that there exist 4 adsorption sites which are the top, bridge, hexagonal close packing （hcp）, and face cen- tered cubic （fcc） sites. C--O bond is perpendicular to the metal surface and the C atom is in the near-metal posi- tion in the stable state of all adsorption sites. All of the stable states are non-dissociative adsorption states. The properties of CO adsorbed on the fcc and hcp sites are almost the same. The adsorption process of CO and H on Ni （111 ） surface is studied next, and the results showed that CO combined with H to generate the intermediate spe- cies --OCH and --COH. By analyzing the C--O bond length and the stretching vibration frequency, it is found that the C--O bond is largely weakened. The C--O bond can be broken down more easily in the active site compa- ring with CO adsorption without H. Therefore, with metal Ni （111 ） surface as catalyst, the added hydrogen is helpful for the dissociation of CO.

关 键 词：密度泛函 Ni(111) CO+H 费托合成 吸附 

分 类 号：O621[理学—有机化学]