Rapid and stable electrolysis of CO2-saturated bicarbonate solution to CO using a self-supported nano Ag mesh electrode

The use of alkaline gas flow cells for electrochemical CO 2 reduction reaction (CO 2 RR) has achieved industrial current density ( j > 200 mA/cm 2 ), but it still faces great challenges in operational stability due to salt precipitation. Direct electrolysis of CO 2 -saturated solution can effectively avoid the salt precipitation issue. However, the current density of the system is largely limited (usually <100 mA/cm 2 ) due to the low mass transfer of CO 2(aq) in aqueous solution and unsuitable electrode structure . Here we report a bipolar membrane (BPM) electrolyzer with a CO 2 -saturated bicarbonate solution feed, employing a self-supported nano Ag electrode instead of the widely used composite carbon electrode. At ambient temperature and pressure, we achieved a Faradaic efficiency of CO (FE CO ) up to 97.29 %, with a maximum j CO of 632.67 mA/cm 2 and stability exceeding of 350 h (FE CO > 90 %). These performance metrics surpass most of bicarbonate-fed electrolyzers and offer significant advantages compared to the electrolyzers using gaseous CO 2 feedstocks . In addition, the self-supported nano Ag electrode offers a simple preparation process compared to the composite carbon electrodes, making it advantageous for large-scale production. • The nano Ag mesh electrode, highly catalytic and long-term stable, is proposed. • The nano Ag mesh electrode shows a CO partial current density of 632.67 mA/cm 2 . • Electrolyzed CO 2 -saturated bicarbonate solution exhibits >350 h stability.