| 水与金属表面作用的第一原理计算 | |
| Alternative Title | Structure and bonding of water on metals from first-principles |
| 李佶彪 | |
| Subtype | 博士 |
| Thesis Advisor | 王福会 |
| 2009-05-31 | |
| Degree Grantor | 中国科学院金属研究所 |
| Place of Conferral | 金属研究所 |
| Degree Discipline | 材料学 |
| Keyword | 表面水 吸附结构 第一原理 过渡金属 电子结构 |
| Abstract | 水在金属表面的吸附在有关宇宙、大气、生物、腐蚀、催化等界面现象中起着重要的作用，成为多学科共同关注的前沿课题，其中心问题是水如何与金属表面作用，这种作用如何决定对表面水(冰)的吸附相结构和水(冰)的初始形核方式，然而人们至今对这两个问题的理解还处于初始阶段。在工业技术领域，与这两个问题直接相关的一个突出例子是燃料电池催化反应，其中水及其组分与金属催化剂表面的润湿作用是影响阴极氧还原反应(ORR)速率的重要因素。 在本论文中，我们运用密度泛函理论计算了不同比例的质子参与氢键作用下的表面水的吸附几何结构和电子结构。即研究了金属表面几何结构(例如Pd(111)、Pd(100)、Pd(110))和电子结构(例如Ni(111)和Pd(111))如何决定在没有氢键参与下的水分子单体与这些表面的作用，并如何影响水分子单体的表面基元运动(例如，Pd(111)、Pd(100)、Pd(110)、Al(100))。研究了部分质子参与氢键作用下的水分子单层(例如H2O/Pd(110))和质子完全参与氢键作用的H2O-OH混合吸附单层(例如H2O-OH /Pd(110)、H2 本论文为HO-OH/Pd(111))。 2O-Pd键合的电子结构提供了一个完整统一的认识(JPCC, 2009, 113, 1931; PRB, 2007, 76, 235433)，确认了水分子单体在Ni(111)面吸附的全新的键合方式(JPCC, 2008, 112, 8301)。该结果对ORR催化反应有直接的指导意义，即合成{110}表面结构主导的纳米结构和Pt(Pd)表面合金化作为提高阴极反应效率的两种途径的根源是改变了d轨道与水分子的作用方式。除了得到H2O-OH混合吸附层的表面相结构外，本论文还报道了分子态单层水在Pd(110)面更为合理的表面相结构, 而且分子间氢键作用和水-金属作用之间的竞争是上述表面结构的决定因素。发现OH的出现使得两种作用之间的关系由竞争转变为协同，即氢键和H2O-Pd作用同时增强，这种协同反而使吸附层在靠近真空一侧的电荷密度增加，从而为电荷密度消耗作为单层憎水性的判据提供了反例。 |
| Other Abstract | Water adsorption on metals is extremely important in a large number of interfacial phenomena related to astrochemical ice nucleation, atmospheric chemistry, heterogeneous catalysis, electrochemical and corrosion processes. For instance, the interaction of water and its constituents determine the kinetics of the oxygen reduction reaction (ORR) in fuel cell catalysis. Nonetheless, little is known about structures of water interaction with well-defined single crystal metal surfaces. Questions regarding how water, at various degrees of coverage, interfaces with the metal surfaces and what factors govern the water-metal bonding have not been satisfactorily addressed. In this thesis, ab initio density functional theory has been used to study the adsorption of water on low-Miller-index Pd surfaces by varying the amount of protons involved in H-bonding of water adlayers, ranging from supported H2O monomers with no hydrogen bonding, to intact H2O monolayers in which a number of protons contribute to H-bonding, to H2O-OH mixed phases where all protons are involved in H-bonding. On the basis of orbital analysis, we have provided a complete understanding of geometrical and electronic effects on water-palladium bonding as well as molecular mechanisms of elementary surface diffusion of the water monomers on Pd(111), Pd(100), Pd(110) and Al(100). A new bonding mechanism for a water monomer on Ni(111) and unique molecular mechanisms for atop-to-atop motions have been identified. Several structural models for intact H2O monolayers on M(110) surfaces (M=Pd, Cu, Ni) are proposed, and the rotated H-down structures have been found to be the most promising ground-state structures of the water adlayers, as compared to the H-down monolayer model. The coplanar atomic structures of mixed H2O/OH phases on Pd(111) and Pd(110) have also been determined. We observed that the competition between H-bonding and water-metal bonding actually govern the structures of the intact water monolayers on Pd(110), while in mixed H2O/OH phases, a synergistic effect of the interplay of water-palladium interaction and hydrogen bonding accounts for coplanar adlayer structures and the enhanced electron density which gives rise to the hydrophobic nature of the supported mixed phases on Pd(111) and Pd(110). |
| Pages | 131 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.imr.ac.cn/handle/321006/17217 |
| Collection | 中国科学院金属研究所 |
| Recommended Citation GB/T 7714 | 李佶彪. 水与金属表面作用的第一原理计算[D]. 金属研究所. 中国科学院金属研究所,2009. |
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