Ionic liquids for CO₂ electroreduction: Structurally tunable and functionally versatile electrocatalytic platforms

Ionic liquids (ILs), as structurally tunable and functionally diverse molecular platforms, offer unique advantages in the electrocatalytic reduction of carbon dioxide. With their wide electrochemical windows, high CO₂ solubility, and designable ion-pair structures, ILs function beyond conventional electrolytes or solvents. They can modulate the interfacial microenvironment, stabilize key intermediates, and suppress parasitic hydrogen evolution, thereby enhancing the catalytic efficiency and product selectivity. Recent advances have expanded IL applications into multifunctional electrocatalytic systems, including those coupled with light, electric fields, and pH stimuli. This review, structured around “structure–function–mechanism”, systematically summarizes the roles and regulatory strategies of ILs in CO₂ reduction reaction (CO₂RR). We compare the representative cationic frameworks, imidazolium, pyridinium, and quaternary ammonium, and analyze their effects on CO₂ activation and product distribution. The diverse roles of ILs as electrolytes, co-solvents, and catalyst modulators are discussed in detail. In situ characterization and theoretical simulations are highlighted for their insights into interfacial behavior and mechanistic understanding. Beyond electrocatalysis, the emerging integration of ILs into functional materials and hybrid systems is explored. Despite their promise, challenges such as high viscosity and limited mechanistic clarity remain. To address these issues, we propose a multidimensional optimization framework spanning molecular design, interfacial engineering, and system integration. This review aims to provide a comprehensive perspective on the strategic deployment of ILs in CO₂RR and to offer guidance for advancing efficient electrocatalytic systems toward carbon-neutral energy technologies.