Upscaling studies for efficiently electric-driven CO2 reduction to CO in ionic liquid-based electrolytes

Electric-driven CO 2 reduction to high value-added chemicals is a potential way to solve the carbon emissions. However, the current studies on CO 2 electroreduction (CO 2 ER) are mainly focused on design and preparation of novel electrocatalysts and electrolytes. The large-scale of CO 2 ER is puzzled in the serious hydrogen evolution reaction (HER) in aqueous electrolytes and inferior reaction stability in an enlarged CO 2 electrolyzer. Ionic liquids (ILs) as electrolytes have opened great opportunities for CO 2 ER due to their unique advantages. Herein, a large-scale CO 2 ER device containing an upscaling modified H-type flow cell using IL-based electrolytes (UHFC-IL) with the largest electrode active area of 495 cm 2 was established for CO 2 ER studies. The influences of key operating parameters, such as compositions of IL-based electrolytes, electrolytes velocity, CO 2 gas flow rate and cell voltage on CO 2 ER performance were systematically investigated. A high CO 2 ER performance under the optimum operating conditions achieves 83.9% Faraday Efficiency (FE) for CO with a reaction current of 6.32 A, suppressing HER to only 2% FE. After 10 hr continuous operation, the CO selectivity in IL-based electrolytes is 51.3% higher than that in 0.1 M KHCO 3 aqueous electrolytes, which maintains excellent stability with a high CO generation rate of 1.7 L hr -1 . In addition, the mechanism of CO 2 ER to CO boosted by IL-based electrolytes in UHFC-IL was proposed. This study provides experimental parameters and guidance for future research on the amplification process of CO 2 ER.