In Situ Electropolymerizing Toward EP‐CoP/Cu Tandem Catalyst for Enhanced Electrochemical CO2‐to‐Ethylene Conversion

Electrochemical CO2 reduction has garnered significant interest in the conversion of sustainable energy to valuable fuels and chemicals. Cu‐based bimetallic catalysts play a crucial role in enhancing *CO concentration on Cu sites for efficient C─C coupling reactions, particularly for C2 product generation. To enhance Cu's electronic structure and direct its selectivity toward C2 products, a novel strategy is proposed involving the in situ electropolymerization of a nano‐thickness cobalt porphyrin polymeric network (EP‐CoP) onto a copper electrode, resulting in the creation of a highly effective EP‐CoP/Cu tandem catalyst. The even distribution of EP‐CoP facilitates the initial reduction of CO2 to *CO intermediates, which then transition to Cu sites for efficient C─C coupling. DFT calculations confirm that the *CO enrichment from Co sites boosts *CO coverage on Cu sites, promoting C─C coupling for C2+ product formation. The EP‐CoP/Cu gas diffusion electrode achieves an impressive current density of 726 mA cm−2 at −0.9 V versus reversible hydrogen electrode (RHE), with a 76.8% Faraday efficiency for total C2+ conversion and 43% for ethylene, demonstrating exceptional long‐term stability in flow cells. These findings mark a significant step forward in developing a tandem catalyst system for the effective electrochemical production of ethylene. In situ electropolymerizing yields the EP‐CoP/Cu tandem catalyst, which demonstrates outstanding performance with a remarkable current density of 726 mA cm−2 at −0.9 V versus RHE, high Faradaic efficiencies of 77% for C2 and 43% for ethylene, alongside impressive long‐term durability in GDE‐based flow cells.