Ionic liquids are promising materials for many energy-related applications, including as electrolytes for batteries and capacitors, for dissolution of biomass for conversion to liquid fuels, and for capture and sequestration of carbon dioxide. Some of the many reasons for this are that they are intrinsic electrolytes; they have vanishingly small vapor pressures; and the chemical composition of the molecular anions and cations can is easily changed to make for designer solvents.
Recent studies in our group combine high-energy X-ray scattering and molecular dynamics simulations to understand the structural properties of ionic liquids. Deconstruction of the liquid structure factor reveals three fundamental lengths scales for ordering in these fragile glass-forming liquids. Additional studies of these liquids at interfaces will be discussed. In collaboration with our surface science colleagues, ultrathin films of 1-10 monolayers of ionic liquids have been prepared on Cu(100) and Au(111), and studied extensively by X-ray photoelectron spectroscopy and STM. Our most recent results include experiments on these liquids at the mica interface, studied by atomic force microscopy.