物理化学学报 >> 2009, Vol. 25 >> Issue (12): 2513-2518.doi: 10.3866/PKU.WHXB20091201

研究论文 上一篇    下一篇

水分子和二氧化铈(111)表面相互作用的DFT+U研究

王清高, 杨宗献, 危书义   

  1. 河南师范大学物理信息与工程学院, 河南 新乡 453007; 河南省光伏材料重点实验室, 河南 新乡 453007
  • 收稿日期:2009-06-08 修回日期:2009-08-09 发布日期:2009-11-27
  • 通讯作者: 杨宗献 E-mail:yzx@henannu.edu.cn

DFT+U Study on the Interaction of Water Molecule and Ceria (111) Surface

WANG Qing-Gao, YANG Zong-Xian, WEI Shu-Yi   

  1. College of Physics and Information Engineering, Henan Normal University, Xinxiang, Henan Province 453007, P. R. China; Henan Key Laboratory of Photovoltaic Materials, Xinxiang 453007, Henan Province, P. R. China
  • Received:2009-06-08 Revised:2009-08-09 Published:2009-11-27
  • Contact: YANG Zong-Xian E-mail:yzx@henannu.edu.cn

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摘要：

采用引入Hubbard参数U修正的密度泛函理论(DFT+U)方法, 对水分子在二氧化铈(111)表面的吸附作用进行了研究. 计算结果表明: 在氧化的二氧化铈(111)表面, 水分子以单氢键构型吸附在二氧化铈表面, 但是不能自发解离; 在还原的二氧化铈(111)表面, 水分子或化学吸附在衬底上, 或自发解离成表面羟基结构. 与氢气在氧化的二氧化铈(111)表面上物理吸附体系的总能相比, 羟基化表面构型是能量更低的构型, 所以羟基解离形成氢气, 从而使表面被氧化的过程需要有外部条件, 反应不能自发进行. 因此, 水分子在还原的二氧化铈(111)表面有两个可能的状态, 即无氢键结构的化学吸附和表面羟基结构的解离吸附. 在一定的外部条件下, 表面羟基结构进一步解离形成氢气, 并使还原的二氧化铈(111)表面得以氧化.

关键词: 二氧化铈, 密度泛函理论, 水分子, 羟基

Abstract:

The interaction of water molecule and a ceria (111) surface was investigated using DFT+U (density functional theory with the inclusion of on-site Coulomb interaction by introducing Hubbard U parameter) method. The results showthat water molecules adsorb on the oxidized ceria (111) surface through a single H-bond configuration and they do not decompose. On a reduced ceria (111) surface, the water molecules adsorb through a non-H-bond configuration. Furthermore, water molecules prefer to dissociate and form a hydroxyl surface. The hydroxyl surface is much more stable than the physisorption state of H2 on the oxidized ceria (111) surface. In other words, reoxidation of the reduced ceria (111) surface through the dissociation of the hydroxyl surface and the generation of H2 molecules is an endothermic process. Therefore, there are mainly two adsorption states for water molecules on the reduced ceria (111) surface: i) chemisorption through a non-H-bond configuration and ii) dissociative adsorption with a hydroxyl surface. The hydroxyl surface may dissociate under certain conditions and reoxidize the reduced ceria (111) surface.

Key words: Ceria, Density functional theory, Water molecule, Hydroxyl