Favoring CO Intermediate Stabilization and Protonation by Crown Ether for CO2 Electromethanation in Acidic Media

Abstract The large‐scale deployment of CO 2 electroreduction is hampered by deficient carbon utilization in neutral and alkaline electrolytes due to CO 2 loss into (bi)carbonates. Switching to acidic media mitigates carbonation, but suffers from low product selectivity because of hydrogen evolution. Here we report a crown ether decoration strategy on a Cu catalyst to enhance carbon utilization and selectivity of CO 2 methanation under acidic conditions. Macrocyclic 18‐Crown‐6 is found to enrich potassium cations near the Cu electrode surface, simultaneously enhancing the interfacial electric field to stabilize the *CO intermediate and accelerate water dissociation to boost *CO protonation. Remarkably, the mixture of 18‐Crown‐6 and Cu nanoparticles affords a CH 4 Faradaic efficiency of 51.2 % and a single pass carbon efficiency of 43.0 % toward CO 2 electroreduction in electrolyte with pH=2. This study provides a facile strategy to promote CH 4 selectivity and carbon utilization by modifying Cu catalysts with supramolecules.