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

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 .