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.