ICC: A Combined Computational and Spectroscopic Study of Structure and Charge Transfer Dynamics of Ionic Liquids in Heterogeneous Environments

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Ionic liquids (ILs) are a relatively new class of materials with great potential for applications in energy devises. The collaborative research proposed here aims at obtaining a quantitative understanding of structure and dynamics of ionic liquids and their mixtures with organic co-solvents in nano-sized environments, including interfaces with microporous graphitic materials and metal-organic frameworks (MOFs), via a combined effort in computational chemistry (quantum chemistry and simulations) and spectroscopy (IR, Raman, X-ray and inelastic neutron scattering). Our primary focuses are: (1) respective roles played by ions and co-solvent molecules and their interplay as well as roles by micropores in modulating structural and dynamic properties of ILs, (2) their measurements via vibrational, X-ray and inelastic neutron scattering experiments and (3) analysis of electronic structure and charge transfer properties of ILs and their variations with solvation structures inside the pores. By integrating complementary strengths of US and UK groups synergistically, the proposed research will provide novel chemical insights into, and thus advance our fundamental understanding of, technologically-relevant IL-graphene and related interfacial systems that have broad applications in energy storage and conversion devices, such as supercapacitors, rechargeable batteries, photovoltaics and fuel cells, as well as in catalysis.The US group will perform MD simulations and analyze structure and dynamics of ILs (and their mixtures with organic additives) in microporous MOF and carbon environments. Using the structural information thus obtained, they will perform quantum chemistry calculations to analyze vibrational spectra of ILs and investigate charge transfer of ions near the surface. The UK groups will investigate the same systems using vibrational, X-ray and inelastic neutron scattering spectroscopy to obtain a comprehensive understanding of molecular interactions and structures at the interface. Through a detailed comparison of computational and experimental results, molecular conformations of ions (and cosolvent molecules) in the real system will be identified and a structural interpretation of the measured spectra will be made. This will shed important light on how interactions of ions and heterogeneous environments are manifested in vibrational and X-ray spectra. It will also provide molecular-level insight into how structural changes of ILs induced by nano-scale environments influence their chemical reactivity.Through extended research visits to the foreign collaborators' labs, the proposed collaboration will provide excellent training and growth opportunities for junior scientists involved in the project. In particular, active collaboration with people with totally different expertise (i.e., theory vs experiments) in different research and cultural environments will be an invaluable experience that would both deepen and broaden not only technical skills and scientific knowledge of junior researchers but also their perspectives on science and its globalization. Key results of the research will be incorporated into web-based chemistry educational software, ChemCollective, developed at Carnegie Mellon University. This will help to disseminate the outcome of the research in the energy context to a broader audience, including undergraduate and high school students. This will also help to increase their awareness of energy and sustainability.