(186c) Insight into Nonaqueous Solvent Transition Metal Interfaces from First Principles Calculations

Nonaqueous electrolytes and their interfaces with metal electrodes have been studied experimentally for many years. Nonaqueous electrolytes are used in a variety of electrochemical systems, and many nonaqueous solvents are available which possess diverse and unique properties. Experiments demonstrate that the properties of the electrolyte, including the solvent, critically influence the selectivity and activity of electrochemical processes. Interfacial effects resulting from interactions between electrolyte species and the metal surface are hypothesized to influence these solvent and electrolyte effects. But relatively little is definitively known about the detailed structure and interactions at these interfaces due to the limitations of spectroscopic methods in studying room-temperature interfaces between condensed phases. Furthermore, nonaqueous metal interfaces have not been extensively studied theoretically, due to the computational expense of sampling first principles calculations over a representative ensemble of solvent configurations.

In this work, we perform a computational study of nonaqueous metal interfaces on a range of transition metals and surface facets. The metals studied span a reactivity range from very noble (silver) to increasingly reactive (e.g. rhodium). We use density functional theory coupled with a global optimization algorithm to model interactions between the solvent and the metal over a large set of configurations. We describe the dependence of solvent chemisorption and interfacial structure on metal, surface facet, and interfacial electrostatic field, and relate these findings to experimental results. We study the relationship between the metal work function and the potential of zero charge (PZC). We find that solvent chemisorption has significant effects on the work function – PZC relationship and investigate metal and facet dependence of these effects. This sheds new light on the experimentally observed facet and metal dependence of the relationship between metal work function and PZC, providing fundamental understanding relevant to many electrochemical systems.