Solvation Properties of Silver and Copper Ions in a Room Temperature Ionic Liquid: A First-Principles Study

Abstract

Understanding the behavior of metal ions in room temperature ionic liquids (ILs) is essential for predicting and optimizing performance for technologies like metal electrodeposition; however, many mechanistic details remain enigmatic, including the solvation properties of the ions in ILs and how they are governed by the intrinsic interaction between the ions and the liquid species. Here, we utilize first-principles molecular dynamics simulations to unravel and compare the key structural properties of Ag+ and Cu+ ions in a common room temperature IL, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. We find that, when compared to Cu+, the larger Ag+ shows a more disordered and flexible solvation structure with a more frequent exchange of the IL species between its solvation shells. In addition, our simulations reveal an interesting analog in the solvation behavior of the ions in the IL and aqueous environments, particularly in the effect of the ion electronic structures on their solvation properties. This work provides fundamental understanding of the intrinsic properties of the metal ions in the IL, while offering mechanistic understanding and strategy for future selection of ILs for metal electrodeposition processes.

Structural Anomalies and Electronic Properties of an Ionic Liquid under Nanoscale Confinement

“…Due to a suite of attractive and widely tunable physiochemical properties, roomtemperature ionic liquids (ILs) have emerged as highly promising electrolytes in a wide range of technologies, including catalysis, 1 ion batteries, 2 CO2 capture, 3 electrodeposition, [4][5][6] and supercapacitors. 7,8 Both experimental and computational studies highlighted that understanding the detailed structure and arrangement of ions in porous electrodes is essential for optimizing performance for many of these applications.…”

“…Due to a suite of attractive and widely tunable physiochemical properties, room-temperature ionic liquids (ILs) have emerged as highly promising electrolytes in a wide range of technologies, including catalysis, ion batteries, CO 2 capture, electrodeposition, − and supercapacitors. , Both experimental and computational studies highlighted that understanding the detailed structure and arrangement of ions in porous electrodes is essential for optimizing performance for many of these applications. − A prime example by Chmiola et al indicated that an optimal capacitance is achieved when ion size matched that of the pore, which was attributed to distortion of the ion solvation under spatial confinement. , However, since this initial discovery, detailed and comprehensive structural insights have been slow to evolve, because electrolyte behavior at interfaces and under confinement is challenging to resolve. These characteristics are especially intractable for emergent electrolytes like ILs, which exhibit bulky, flexible, and widely varying molecular configurations.…”