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

The high-rate electrocatalytic CO 2 reduction reaction (CO 2 RR) to afford multicarbon products (C 2 ) holds transformative potential for advancing sustainable energy systems. Ionic liquids (ILs) have emerged as dynamic modulators to promote the C 2 pathway, yet the underlying atomistic mechanisms of ILs in modulating this CO 2 RR 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 CO 2 RR pathway on Cu surfaces through electronic structure engineering. MD simulations demonstrate that ILs establish a CO 2 -enriched interfacial microenvironment that restricts bulk-phase CO 2 diffusion through the confinement effect. Electron structure analyses reveal that ILs synergistically enhance interfacial electron accumulation and directional charge transfer for adsorbed CO 2 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 CO 2 RR to C 2 H 4 and C 2 H 5 OH pathways through atom orbital hybridization. Additionally, the ILs not only enhance the CO 2 RR 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 CO 2 RR processes and offers a foundation for designing advanced IL-mediated electrocatalytic systems.