Highly Efficient Electrocatalytic CO₂ Reduction to C₂₊ Products on a Poly(ionic liquid)-Based Cu⁰ -Cu^I Tandem...

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 -Cu^I tandem catalyst for the production of C₂₊ products with both high reaction rate and high selectivity. Remarkably, a high C₂₊ 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 Cu⁰ -PIL-Cu^I interfaces are vital for such reactivity. Specifically, Cu nanoparticles derived Cu⁰ -PIL interfaces account for high current density and a moderate C₂₊ 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 C₂₊ selectivity by lowering the barrier of C-C coupling.