Collaborative Research: Structure and Thermodynamics of Ionic Liquids at Solid Surfaces: the Return of Water

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Ionic liquids (ILs) have interesting physicochemical properties, including low volatility, high thermal stability, high CO2 solubility and selectivity, and unique solvation characteristics, making them promising candidates for applications involving CO2 capture, catalysis, and dispersion of colloidal particles. This collaborative project will combine experiments and molecular simulations aiming to understand the role of interfacial water at the interface between ILs and solid surfaces. The role of interfacial water on the electrification of solid surfaces and the structure of interfacial ILs will be investigated and its impact the CO2 adsorption at IL-solid interfaces will be studied. The proposed research aims to investigate the role of water on the interfacial structure of ILs and address the three-way coupling among surface electrification, water adsorption and ion self-assembly in the interfacial zone, which is crucial for resolving existing controversies on the effect of water on solid-IL interfaces. A multi-faceted experimental characterization (e.g., attenuated total reflectance Fourier transform infrared spectroscopy, X-ray reflectivity, and neutron reflectivity) will be integrated with computer simulations to obtain high-quality data and mechanistic insights on the effect of water on the structure of solid-IL interfaces and gas adsorption at these interfaces. This will help settle the controversies in the literature and provide guidelines for applications such as CO2 capture. To investigate how water affects the electrification of solid surfaces and the structure of interfacial ILs, mica will be used as the solid surface to test the hypotheses that water enables electrification of solid surfaces by effective dissolution of surface ions and impacts self-assembly of ILs via water-IL coupling. To investigate how water impacts the CO2 adsorption at IL-solid interfaces, silica will be used as the solid surface because of its relevance to applications including CO2 capture and catalysis. The insights gained from this project may enable the tailoring of solid-IL interfaces and gas adsorption at these interfaces by controlling the water content. In addition to training graduate students and developing new courses, the investigators plan to offer research opportunities to undergraduate students from underrepresented groups and pursue outreach activities to K12 students in collaboration with the Engineering Advancing Grade-school Education (ENGAGE) program at the University of Pittsburgh and the Center for the Enhancement of Engineering Diversity (CEED) at Virginia Tech.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.