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

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 (FE C2+ ) 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.