Industrial activities lead to a substantial share of current anthropogenic CO₂ emissions and are some of the most challenging to abate. Direct utilization of industrial flue gases to produce fuels or value-added chemicals is challenging due to the presence of impurities and low concentrations of CO₂. Herein, we demonstrate a rational assembly of a permselective gas diffusion electrode (PGDE) for direct CO₂ conversion from quasi flue gas (i.e., 10–15% CO₂, 4% O₂, and N₂ balance at 100% relative humidity). The electrode design consists of a metal–organic framework (MOF) based mixed matrix membrane (MMM) that enables the selective permeation of CO₂ to a silver electrocatalyst. The MOF is CALF-20, notable for the ability to physisorb CO₂ in wet gas streams. Applying this approach, we convert N₂-diluted CO₂ streams to CO at a faradaic efficiency of 95% compared to 58% for the nonmodified counterpart electrode with MMM. The PGDE retained its electrochemical performance when introducing O₂ by preventing ∼84% loss of current toward parasitic oxygen reduction reaction (ORR) and reported 30 mA cm^–2 CO partial current density. Further, wetting the gas stream showed a negligible effect on the MOF and the electrochemical performance. Using our PDGE, we report nearly constant CO selectivity over 19 h in a membrane electrode assembly electrolyzer. This approach offers the potential for direct utilization of low-concentration CO₂ while avoiding the economic and environmental costs of obtaining purified CO₂ feedstocks.

中文翻译：

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用于从准烟气中直接转化 CO2 的选择性渗透 MOF 基气体扩散电极

工业活动导致当前人为 CO ₂排放量的很大一部分，并且是最具挑战性的减排活动。_{由于存在杂质和低浓度的 CO 2}，​​直接利用工业烟气生产燃料或增值化学品具有挑战性。在此，我们演示了选择性渗透气体扩散电极 (PGDE) 的合理组装，用于从准烟气中直接转化CO ₂ （即，在 100% 相对湿度下平衡10–15% CO ₂、4% O ₂和 N ₂ ） . 电极设计由基于金属有机骨架 (MOF) 的混合基质膜 (MMM) 组成，可选择性渗透 CO ₂到银电催化剂。MOF 是 CALF-20，以在湿气流中物理吸附 CO _{2的能力而著称。}应用这种方法，我们以 95% 的法拉第效率将 N ₂稀释的 CO ₂流转化为 CO ，而使用 MMM 的未修改对应电极的法拉第效率为 58%。_{PGD​​E 在引入 O 2}时通过防止寄生氧还原反应 (ORR) 损失约 84% 的电流来保持其电化学性能，并报告了 30 mA cm ^–2CO分电流密度。此外，润湿气流对 MOF 和电化学性能的影响可以忽略不计。使用我们的 PDGE，我们报告了在膜电极组件电解槽中 19 小时内几乎恒定的 CO 选择性。这种方法提供了直接利用低浓度 CO ₂的潜力，同时避免了获得纯化 CO ₂原料的经济和环境成本。