Highly Efficient Electrocatalytic CO2 Reduction to C2+ Products on a Poly(ionic liquid)‐Based Cu0–CuI Tandem Catalyst

Abstract Electroreduction of CO 2 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 Cu 0 –Cu I tandem catalyst for the production of C 2+ products with both high reaction rate and high selectivity. Remarkably, a high C 2+ faradaic efficiency (FE ) 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 Cu 0 ‐PIL‐Cu I interfaces are vital for such reactivity. Specifically, Cu nanoparticles derived Cu 0 ‐PIL interfaces account for high current density and a moderate C 2+ selectivity, whereas Cu I species derived PIL‐Cu I interfaces exhibit high activity for C−C coupling with the local enriched *CO intermediate. Furthermore, the presence of the PIL layer promotes the C 2+ selectivity by lowering the barrier of C−C coupling.