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.