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

Bicarbonate electrolyzer can achieve the direct conversion of CO 2 capture solutions that bypasses energy-intensive steps of CO 2 regeneration and pressurization. However, only single-carbon chemicals (i. e., CO, formate, CH 4 ) were reported as the major products so far. Herein, bicarbonate conversion to multicarbon (C 2+ ) 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 CO 2 was first reduced to CO on the Ag layer, followed by its favorable further reduction to C 2+ 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-C 2+ conversion and suppress the hydrogen evolution reaction. Subsequently, a maximum C 2+ faradaic efficiency of 41.6±0.39 % was achieved at a considerable current density of 100 mA cm -2 .