Solvation at interfaces in real space – from solvatomers to closed layers

本研究旨在通过低温扫描隧道显微镜（LT-STM）在分子尺度上研究仅限于单晶金属表面的碱和土碱吸附剂的溶剂化，从微观角度研究离子溶剂化及其对水岛形成的影响。金属表面离子与水分子相互作用的光谱和微观研究是基础科学的一个课题。最近，这种混合界面被应用于电化学、燃料电池、电池和其他能量收集设备，展现了对其基本理解的技术方面。本课题拟采用LT-STM对Au（111）表面碱金属和碱土金属与水共吸附界面进行结构研究。具体而言，本研究寻求对一系列不同大小的碱离子（Li+, Na+, Rb+, Cs+）和两种不同大小的土碱离子（Mg2+和Ba2+）的结构见解，这些碱离子与D2O共吸附。我们将主要探索Au(111)（反应性最低的过渡金属表面）上的溶剂化离子，以演示如何获得与表面接触的溶剂化壳层的原子尺度图像。Au（111）是电催化的典型表面，是研究离子溶剂化的理想模型体系。它具有表面重建的警告，即所谓的人字形重建，导致大量不同的吸附位点，fcc, hcp，结构域边界和肘部位点。尽管我们提出溶剂化体不会受到不同吸附位点的广泛影响，忽略肘部位置，但警告要求与非重构表面进行比较。我们选择Cu(111)，一个更活泼的过渡金属表面，因为它最近成为一个模型系统，以遵循离子和溶剂的去离子化动力学。这项工作的主要目的是精确表征表面支持的溶剂化体，并确定离子的大小和电荷状态如何影响相互作用，它们的相互作用，以及更大的水结构的结构。该提案将是第一个提供金属界面上溶剂化壳的原子尺度信息的研究，这对于理解离子对界面反应性的影响至关重要。

The proposed work aims to add a microscopic view of ion solvation and its effect on water island formation by using low-temperature scanning tunnelling microscopy (LT-STM) to study the solvation of alkali and earth-alkali adsorbates confined to single-crystal metal surfaces on the molecular scale. The spectroscopic and microscopic investigation of the interaction of ions with water molecules on metal surfaces is a topic of basic science. Recently, such hybrid interfaces were applied in electrochemistry, fuel cells, and battery and other energy harvesting devices, unfolding the technological aspect of its fundamental understanding. The proposed research program intends to structurally investigate an interface of alkali and alkaline earth metals co-adsorbed with water on an Au (111) surface by LT-STM. Specifically, the present research seeks structural insight into a range of differently sized alkali ions, Li+, Na+, Rb+, Cs+, and two earth alkali ions of disparate size, Mg2+, and Ba2+, co-adsorbed with D2O. We will mainly explore solvated ions on Au(111), the least reactive transition metal surface, to demonstrate how to achieve an atomic-scale picture of solvation shells in contact with a surface. Au(111) is a prototypical surface for electrocatalysis and an ideal model system to study the solvation of ions. It has the caveat of surface reconstruction, the so-called herringbone reconstruction, leading to a multitude of different adsorption sites, fcc, hcp, domain boundaries, and elbow sites. Though we propose that the solvatomers will not be broadly influenced by different adsorption sites, disregarding the elbow sites, the caveat demands comparison to a non-reconstructed surface. We chose Cu(111), a more reactive transition metal surface, because it recently became a model system to follow the dynamics of the deionization of ions and solvatomers. The principle aim of the work is to precisely characterize the surface-supported solvatomers and determine how the size and the charge state of the ions influence the interactions, their interplay, and the structure of larger water structures. This proposal will be the first study that delivers atomic-scale information about solvation shells at metal interfaces, essential for the understanding of the influence of the ions on reactivity at interfaces.