Diversity at the Water-Metal Interface: Metal, Water Thickness, and Confinement Effects.
Diversity at the Water-Metal Interface: Metal, Water Thickness, and Confinement Effects.
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DOI：
10.1021/acscentsci.5b00349
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发表时间：
2016-02-24
影响因子：
18.2
通讯作者：
López N
中科院分区：
文献类型：
--
作者：
Bellarosa L;García-Muelas R;Revilla-López G;López N
与金属表面接触的水膜的结构和性质对于理解与能源有关的技术中涉及的化学和电化学过程至关重要。用第一性原理分子动力学方法研究了Pd、Pt和Ru表面水膜的性质，以评估水-金属表面的化学作用如何导致靠近金属的水层行为的多样性。液态水的特征：径向分布函数、配位和碎片形态仅出现在最小厚度为1.4纳米的无承压水层中。此外，Pd和Pt的水层在最接近金属的区域较致密，出现七元环和五元环基元。这些模式与通过扫描隧道显微镜对孤立的水双分子层进行鉴定的模式相同。在Ru表面没有观察到界面致密化，水解离，质子和羟基被锁定在表面。因此，金属附近区域的酸碱性质没有受到扰动，这与实验一致，而且主体水类似于双电层。限制作用会影响水，使其在结构和动力学性质上都更接近冰，从而导致在实验中发现的纳米级更高的粘度。所有这些贡献改变了反应物和产物在水-金属界面的溶剂化，并将影响表面的催化和电催化性能。水−金属界面的第一性原理分子动力学表明，水的性质取决于可能改变(电)催化反应性的金属和限制。
The structure and properties of water films in contact with metal surfaces are crucial to understand the chemical and electrochemical processes involved in energy-related technologies. The nature of thin water films on Pd, Pt, and Ru has been investigated by first-principles molecular dynamics to assess how the chemistry at the water–metal surface is responsible for the diversity in the behavior of the water layers closer to the metal. The characteristics of liquid water: the radial distribution functions, coordination, and fragment speciation appear only for unconfined water layers of a minimum of 1.4 nm thick. In addition, the water layer is denser in the region closest to the metal for Pd and Pt, where seven- and five-membered ring motifs appear. These patterns are identical to those identified by scanning tunneling microscopy for isolated water bilayers. On Ru densification at the interface is not observed, water dissociates, and protons and hydroxyl groups are locked at the surface. Therefore, the acid–base properties in the area close to the metal are not perturbed, in agreement with experiments, and the bulk water resembles an electric double layer. Confinement affects water making it closer to ice for both structural and dynamic properties, thus being responsible for the higher viscosity experimentally found at the nanoscale. All these contributions modify the solvation of reactants and products at the water–metal interface and will affect the catalytic and electrocatalytic properties of the surface. First-principles molecular dynamics of the water−metal interface illustrates that the properties of water depend on the metal and confinement that might alter the reactivity in (electro-)catalysis.