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

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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.