Interfacial Electron Modulation with Ionic Liquids: Dual Optimization of CO₂ Confinement and Charge Transfer for Enhanced Electroreduction on Cu

The high-rate electrocatalytic CO₂ reduction reaction (CO₂RR) to afford multicarbon products (C₂) holds transformative potential for advancing sustainable energy systems. Ionic liquids (ILs) have emerged as dynamic modulators to promote the C₂ pathway, yet the underlying atomistic mechanisms of ILs in modulating this CO₂RR process remain fundamentally unclear. Here, by integrating molecular dynamics (MD) simulations, density functional theory (DFT) calculations, and experimental validations, we systematically elucidate the critical influence of 1-(3-aminopropyl)-3-methylimidazole chloride ILs in optimizing the CO₂RR pathway on Cu surfaces through electronic structure engineering. MD simulations demonstrate that ILs establish a CO₂-enriched interfacial microenvironment that restricts bulk-phase CO₂ diffusion through the confinement effect. Electron structure analyses reveal that ILs synergistically enhance interfacial electron accumulation and directional charge transfer for adsorbed CO₂ and key intermediates (*CO, *COH, *CHO, and *C), collectively stabilizing them through IL-induced strengthening of Cu-C bonding. More importantly, the introduction of ILs dramatically reduces the activation barrier of the rate-determining C-C coupling step and thermodynamically favors the CO₂RR to C₂H₄ and C₂H₅OH pathways through atom orbital hybridization. Additionally, the ILs not only enhance the CO₂RR but also suppress the hydrogen evolution reaction (HER) through proton confinement. This work provides molecular-level insights into the dynamic role of ILs in optimizing CO₂RR processes and offers a foundation for designing advanced IL-mediated electrocatalytic systems.