Optimal Packing of CO at a High Coverage on Pt(100) and Pt(111) Surfaces
Optimal Packing of CO at a High Coverage on Pt(100) and Pt(111) Surfaces
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DOI：
10.1021/acscatal.0c01971
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发表时间：
2020-08-21
期刊：
影响因子：
12.9
通讯作者：
Sautet, Philippe
中科院分区：
文献类型：
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作者：
Sumaria, Vaidish;Nguyen, Luan;Sautet, Philippe
通过密度泛函理论建模研究了Pt(111)和Pt(100)表面上一氧化碳（CO）的高覆盖度结构，并与高压扫描隧道显微镜实验进行了比较。已知半局域交换关联泛函会为Pt上的CO提供错误的吸附位点且高估吸附能。我们利用吸附的CO的键长作为描述符，开发了一种针对Pt(111)和Pt(100)上CO吸附能的简单第一性原理校正方法。能量校正按照顶位<桥位< hollow位的顺序增加，用于推导Pt的111和100晶面上吸附的CO的表面稳定性图，展示了表面上热力学稳定的CO构型随温度和压力的变化。对Pt(111)上CO的高覆盖度（θ>0.5）构型进行系统探究后发现，会在六边形的Pt(111)层上形成叠加的六边形/准六边形CO晶格。然而，在真空和低温条件下看到的非六边形结构，（√3×3）rect - 4CO和c(√3×7)rect - SCO，在相似覆盖度下仅比六边形晶格稳定性低5 meV/Ų。对于θ≥0.75的Pt(100)，CO分子采用一维重合晶格，我们观察到形成了(n×2)晶胞（n = 4、6、8），每个晶胞中有(2n - 2)个CO分子处于顶位/准顶位和桥位/准桥位，形成一个倾斜的六边形晶格，以随着覆盖度增加减少CO - CO排斥作用。计算结果与Pt(111)和Pt(100)的现有实验观察结果相符。综合的理论模拟和实验观察为研究涉及高CO压力的反应中Pt表面的催化活性提供了结构数据，并提出了一种在涉及高CO压力的催化反应过程中理解其他金属催化剂表面上CO分子结构的方法。
High coverage structures for CO on Pt(111) and Pt(100) surfaces are studied by density functional theory modeling and compared to high-pressure scanning tunneling microscopy experiments. Semilocal exchange correlation functionals are known to provide an incorrect adsorption site and overestimated adsorption energy for CO on Pt. We develop a simple first-principles correction for the adsorption energy of CO on Pt(111) and Pt(100) using the bond length of adsorbed CO as a descriptor. The energy correction, which increases in the order top < bridge < hollow site, is used to derive the surface stability diagram for CO adsorbed on 111 and 100 facets of Pt showing the thermodynamically stable CO configurations on the surface as a function of temperature and pressure. High coverage (theta > 0.5) configurations of CO on Pt(111) lead to the formation of superimposed hexagonal/quasi-hexagonal lattice of CO on the hexagonal Pt(111) layer from a systematic exploration of such structures. Non-hexagonal structures seen in vacuum and low temperature conditions, (root 3 x 3)rect-4CO and c(root 3 x 7)rect-SCO, are however only 5 meV/angstrom(2) less stable than the hexagonal lattice at a similar coverage. For Pt(100) at theta >= 0.75, the CO molecules adopt a one-dimensional coincidence lattice and we observe the formation of (n x 2) unit cells (n = 4, 6, 8) with (2n - 2) CO molecules in each cell on top/quasi-top and bridge/quasi-bridge positions creating a skewed hexagonal lattice to reduce CO-CO repulsion with increasing coverage. The computational results agree with the available experimental observations for Pt(111) and Pt(100). The integrated theoretical simulation and experimental observation provide structural data for the study of catalytic reactivity on Pt surfaces in reactions involving high CO pressures and suggest an approach for understanding the structure of CO molecules on other metal catalyst surfaces during the catalytic reactions involving a high pressure of CO.