Kolb Manuel J, Wermink Jasper, Calle-Vallejo Federico, Juurlink Ludo B F, Koper Marc T M
Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC Leiden, The Netherlands.
Phys Chem Chem Phys. 2016 Feb 7;18(5):3416-22. doi: 10.1039/c5cp04468e.
Platinum is an active catalyst for a large number of (electro)chemical reactions in aqueous solution. The observed catalytic activities result from an interplay between the intrinsic adsorption properties of platinum surfaces and their interaction with the aqueous environment. Although water networks have been extensively studied on close-packed surfaces, little is known about high-coverage solvation environments around defects. Here, we report DFT calculations on medium- to high-coverage water adsorption structures near the (100) step edge on Pt(533). We find that isolated ring structures adjacent to step edges form hexagons or pentagons. For higher coverages, 6 possible adsorption structures with varying ring sizes along the step edge and almost identical adsorption energies are observed. From our results we conclude that the favorable interaction of the H-down oriented water molecules, adjacent to the step edge, with the step dipole plays an important role in the formation of these structures. Furthermore, our results explain why water networks on stepped surfaces originate at the step edges, and extend towards the adjacent terraces, in agreement with previous experiments. These results show how step edges act as anchoring points for water adsorption and suggest that solvation of defects might dominate water structures on real platinum surfaces.
铂是水溶液中大量（电）化学反应的活性催化剂。观察到的催化活性源于铂表面的固有吸附特性与其与水环境的相互作用之间的相互影响。尽管水网络在紧密堆积表面上已得到广泛研究，但对于缺陷周围高覆盖率的溶剂化环境却知之甚少。在此，我们报告了关于Pt(533)上(100)台阶边缘附近中高覆盖率水吸附结构的密度泛函理论（DFT）计算。我们发现与台阶边缘相邻的孤立环结构形成六边形或五边形。对于更高的覆盖率，观察到沿台阶边缘具有不同环尺寸且吸附能几乎相同的6种可能的吸附结构。从我们的结果可以得出结论，与台阶边缘相邻的H向下取向的水分子与台阶偶极的有利相互作用在这些结构的形成中起重要作用。此外，我们的结果解释了为什么台阶表面上的水网络起源于台阶边缘，并朝着相邻平台延伸，这与先前的实验一致。这些结果展示了台阶边缘如何作为水吸附的锚定点，并表明缺陷的溶剂化可能主导实际铂表面上的水结构。
