在Pt上的第一层水中发生激烈相互作用和解离
Timo Jacob1, William A Goddard
1Materials and Process Simulation Center, Beckman Institute (139-74), California Institute of Technology, Pasadena, California 91125, USA.
Journal of the American Chemical Society
|July 30, 2004
概括
量子力学计算显示,表面上的水可以形成独特的结构,具有稳定的未分离的双层和近乎稳定的部分分离状态. 这些发现对于理解燃料电池中的催化过程至关重要.
科学领域:
- 表面科学是一门学科.
- 量子力学就是量子力学.
- 催化剂是一种催化剂.
背景情况:
- 表面的水层对于催化过程至关重要,例如燃料电池阴极.
- 之前对的研究表明了新的分离水结构,与的发现形成鲜明对比.
- 了解水与Pt(111) 的相互作用对于优化催化效率至关重要.
研究的目的:
- 使用量子力学方法计算Pt{11}表面第一个水单层的能量和结构.
- 调查Pt上未分离和部分分离的水结构的稳定性.
- 将研究结果与先前关于水与金属相互作用的实验和理论研究进行比较.
主要方法:
- 采用量子力学计算,特别是周期板密度函数理论 (DFT) 与PBE函数.
- 计算了水分子在Pt(111) 表面上被吸附的能量和结构配置.
- 检查了未分离和部分分离的水单层结构.
主要成果:
- 确定了一个稳定的未分离的双层结构,其中水分子与表面平行和垂直 (H-down配置),形成Pt-O和Pt-HO键.
- 一个部分分离的结构,其中一半的水分子分离成Pt-OH和Pt-H,被发现只有稍微不稳定 (0.066 eV/水).
- 未分离的结构表现出~0.42 Å的垂直氧层位移,而部分分离的系统显示出更平坦的结构 (~0.08 Å的分离).
结论:
- 计算的结构证实了对Pt上的H-down未分离水配置的实验观测.
- 在Pt{111}上部分分离水在能量上是可行的,尽管比未分离状态不那么稳定.
- 对于1/3ML以上的覆盖面,有序单层结构是最受欢迎的;在此以下,预计会出现聚类.
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