(349d) Exploring How Interfacial Ion Assembly Accelerates Electrochemical CO2 Reduction

Electrochemical reduction of CO₂ to CO and other valuable products provides opportunities to realize sustainable production of fuels and chemicals. While demonstrated in lab-scale systems, a critical roadblock slowing development of industrial processes is poor understanding of how molecular assembly at electrode-electrolyte interfaces contributes to catalytic activity. Ionic liquids emerged as promising CO₂ reduction electrolytes, since low overpotentials and enhanced product selectivity has been observed for several classes of ionic liquids. However, mechanisms of ionic liquid-mediated catalysis are subject to ongoing discussion. Here, we present our research on tuning the collective assembly of ionic liquids at interfaces to understand ionic liquid-mediated CO₂ reduction at silver surfaces. By tuning ion structures, concentrations, and solvent environments, we reveal that CO₂ reduction to CO in ionic liquids can be accelerated by threefold over prior reports and find unexpected scaling relationships between structure, concentration, and reactivity. Further, we use in situ analysis of electric double layer formation at interfaces, including surface enhanced Raman spectroscopy and surface forces measurements, to yield mechanistic insights into how interfacial ion assembly can accelerate electron transfer to charged intermediates. Notably, our findings point to collective ion assembly as a key factor underpinning structure-reactivity relationships for CO₂ electrochemical reduction. To highlight the impact of this concept, we will discuss how our findings help resolve mechanistic puzzles in ionic liquids electrocatalysis and suggest new strategies for controlling ion and electron flow at interfaces to enhance the conversion of atmospheric CO₂ to CO and other fuel precursors.