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

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