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

Abstract

Electric-driven CO2 reduction to high value-added chemicals is a potential way to solve the carbon emissions. However, the current studies on CO2 electroreduction (CO2ER) are mainly focused on design and preparation of novel electrocatalysts and electrolytes. The large-scale of CO2ER is puzzled in the serious hydrogen evolution reaction (HER) in aqueous electrolytes and inferior reaction stability in an enlarged CO2 electrolyzer. Ionic liquids (ILs) as electrolytes have opened great opportunities for CO2ER due to their unique advantages. Herein, a large-scale CO2ER device containing an upscaling modified H-type flow cell using IL-based electrolytes (UHFC-IL) with the largest electrode active area of 495 cm2 was established for CO2ER studies. The influences of key operating parameters, such as compositions of IL-based electrolytes, electrolytes velocity, CO2 gas flow rate and cell voltage on CO2ER performance were systematically investigated. A high CO2ER 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 KHCO3 aqueous electrolytes, which maintains excellent stability with a high CO generation rate of 1.7 L hr-1. In addition, the mechanism of CO2ER 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 CO2ER.