Abstract Electroreduction of CO2 on a polymer‐modified Cu‐based catalyst has shown high multi‐electron reduction (>2?e?) selectivity, however, most of the corresponding current densities are still too small to support industrial applications. In this work, we designed a poly(ionic liquid) (PIL)‐based Cu0–CuI tandem catalyst for the production of C2+ products with both high reaction rate and high selectivity. Remarkably, a high C2+ faradaic efficiency (FEC2+ ) of 76.1?% with a high partial current density of 304.2?mA?cm?2 is obtained. Mechanistic studies reveal the numbers and highly dispersed Cu0‐PIL‐CuI interfaces are vital for such reactivity. Specifically, Cu nanoparticles derived Cu0‐PIL interfaces account for high current density and a moderate C2+ selectivity, whereas CuI species derived PIL‐CuI interfaces exhibit high activity for C?C coupling with the local enriched *CO intermediate. Furthermore, the presence of the PIL layer promotes the C2+ selectivity by lowering the barrier of C?C coupling.
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