(114f) Mechanistic Role of Ionic Liquids and Alkali Metal Cations in Reactive Carbon Capture

Electrochemical carbon dioxide reduction (CO₂RR) technologies convert greenhouse gases to value added chemicals, potentially helping to decarbonize our energy infrastructure. Simultaneous capture and electro-reduction of CO₂, using room temperature ionic liquids (RTILs) as absorbents and electrolytes, has emerged as emerged as a potential way to reduce the high overpotential requirements of CO₂ activation. Ionic liquids (ILs) species, such as 1-Ethyl-3-methylimidazolium [EMIM]⁺ cation, can form a complex with CO₂ that reduces at the electrocatalytic interface, potentially lowering the CO₂ reduction overpotential. To investigate the mechanistic role of the IL in CO₂ reduction, we develop a multiscale density functional theory and classical molecular dynamics (DFT-MD) modelling framework to look at reaction paths at the electrified interface. This framework uses an analytical grand canonical DFT (a-GCDFT) approach coupled with a coupled electrolyte-polarizable electrode dynamic charge classical MD approach (QDyn) to evaluate reduction energetics. DFT calculations and MD simulations detail the relative populations of IL, solvent, and alkali cations, suggesting more cathodic potentials will increase the ability of smaller alkali cations to outcompete the IL species at the surface. Reduction paths to CO on Ag and Au electrodes show the favorability of paths involving CO₂-[EMIM] dissociation and direct reduction of the bound CO₂ depend on the interfacial electrochemical double-layer properties, making the rates of reduction highly dependent on potential and electrolyte competition. Coordination with the IL cation can be used to both accelerate reduction and open up new reduction paths, with paths involving reduction of the bound CO₂ and [EMIM] ring opening possible for specific combinations of IL and catalyst properties. Collectively, this work illustrates the potential to use the combined DFT-MD approach to guide electrode and electrolyte design for reactive carbon capture, with DFT clarifying catalyst-intermediate binding and MD integrating electrolyte-surface species interactions.