Electrolyzers are now capable of reducing carbon dioxide (CO₂) into products at high reaction rates but are often characterized by low energy efficiencies and low CO₂ utilization efficiencies. We report here an electrolyzer that reduces 3.0 M KHCO₃(aq) into CO(g) at a high rate (partial current density for CO of 220 mA cm^–2) and a CO₂ utilization efficiency of 40%, at a voltage of merely 2.3 V. These results were made possible by using: (i) a reactive carbon solution enriched in KHCO₃ as the feedstock instead of gaseous CO₂; (ii) a cation exchange membrane instead of an anion exchange membrane, which is common to the field; and (iii) the hydrogen oxidation reaction (HOR) at the anode instead of the oxygen evolution reaction (OER). The voltage reported here is the lowest reported for any CO₂ to CO electrolyzer that operates at high current densities (i.e., a partial current density for CO greater than 200 mA cm^–2) with a CO₂ utilization efficiency of greater than 20%. This study highlights how the choice of feedstock, membrane, and anode chemistries affects the rate and efficiency at which CO₂ is converted into products.

中文翻译：

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在低电压和高碳效率下将活性碳溶液转化为 CO

电解槽现在能够以高反应速率将二氧化碳 (CO ₂ ) 还原成产物，但通常以低能量效率和低 CO ₂利用率为特征。我们在此报告了一种电解槽，该电解槽以高速率将 3.0 M KHCO ₃ (aq) 还原为 CO(g)（CO 的部分电流密度为 220 mA cm ^–2），CO ₂利用率为 40%，电压为仅 2.3 V。这些结果是通过使用以下方法实现的：(i) 富含 KHCO ₃的活性碳溶液代替气态 CO _{2作为原料}; (ii) 阳离子交换膜代替本领域常用的阴离子交换膜；(iii) 阳极的氢氧化反应 (HOR) 代替析氧反应 (OER)。这里报告的电压是任何在高电流密度（即，CO 的部分电流密度大于 200 mA cm ^-2）下运行且 CO ₂利用率大于 20%的 CO ₂制 CO 电解槽中报告的最低电压。_{本研究强调了原料、膜和阳极化学成分的选择如何影响 CO 2}转化为产品的速率和效率。