Bicarbonate Electroreduction to Multicarbon Products Enabled by Cu/Ag Bilayer Electrodes and Tailored Microenviroments

Abstract Bicarbonate electrolyzer can achieve the direct conversion of CO2 capture solutions that bypasses energy‐intensive steps of CO2 regeneration and pressurization. However, only single‐carbon chemicals (i. e., CO, formate, CH4) were reported as the major products so far. Herein, bicarbonate conversion to multicarbon (C2+) products (i. e., acetate, ethylene, ethanol, propanol) was achieved on rationally designed Cu/Ag bilayer electrodes with bilayer cation‐ and anion‐conducting ionomers. The in‐situ generated CO2 was first reduced to CO on the Ag layer, followed by its favorable further reduction to C2+ products on the Cu layer, benefiting from the locally high concentration of CO. Through optimizing the bilayer configurations, metal compositions, ionomer types, and local hydrophobicity, a microenvironment was created (high local pH, low water content, etc.) to enhance bicarbonate‐to‐C2+ conversion and suppress the hydrogen evolution reaction. Subsequently, a maximum C2+ faradaic efficiency of 41.6±0.39 % was achieved at a considerable current density of 100 mA cm−2.