Constructing a Localized Buffer Interlayer to Elevate High-Rate CO₂-to-C₂₊ Electrosynthesis

Catalytic surface and interface engineering for the electrosynthesis of multicarbon chemicals from CO₂ are widely investigated, while the selective regulation of mass transport for reactant CO₂ and intermediate CO remains rarely explored, which is a critical challenge limiting the C₂₊ production rate. Here, we strategically construct a buffer interlayer with soluble ionic liquid (IL) additives between the aqueous electrolyte and the catalytic surface, which not only regulates the microenvironment of CO and CO₂ at different reaction stages but also stabilizes catalytic sites. The CO residence time is extended in the buffer interlayer ascribed to the attractive interactions via dipole-dipole interactions and hydrogen bonding. CO₂ and its transport are enhanced by the buffer reactions in the aqueous interlayer within the flow-through compact cell. Meanwhile, the utilization of ILs stabilizes active sites (Cu₂O-derived Cu) by facilitating the regeneration of Cu₂O through the applied potentials. Consequently, C₂₊ products are synthesized at a high rate with a partial current density of 1.30 A/cm² for over 200 h. This concept is further scaled to a 100 cm² flow cell, exhibiting a carbon loss below 6%. Such a systematic investigation establishes a general construction strategy for the buffer interlayer and catalytic sites in electrolysis.