Acidic CO₂ electroreduction reaction (CO₂RR) shows advantages in high carbon utilization efficiency yet encounters great challenges in suppressing undesired hydrogen evolution competition and increasing C₂₊ product selectivity. Although it is known that Cu⁰/Cu⁺ interfaces are conducive to C–C coupling processes, the oxidation state of copper cannot be well maintained under the strong reductive condition and large current electrolysis operation. Herein, we propose an I₂ addition involved strategy to protect the oxidation state of Cu and promote dynamic Cu⁰/Cu⁺ interfaces during acidic CO₂RR. With the addition of I₂ in the electrolyte, a high C₂₊ product Faraday efficiency of above 70% can be achieved at 0.4–0.6 A cm^–2 even under a low K⁺ concentration of 0.3 M, which is comparable to those reported performances with almost ten times higher K⁺ concentrations (2–3 M). This low K⁺ concentration in electrolytes significantly avoids salt crystallization in the CO₂ transport channel to enhance the electrolyzer’s stability. As proved by the surface Pourbaix diagram and experimental results, adding excessive I₂ into the electrolyte boosts the generation of CuI; also, CuI and metallic Cu coexist under electrochemical reduction conditions, demonstrating that a redox loop of Cu → CuI → Cu exists. The loop holds the key to constructing the dynamic Cu⁰/Cu⁺ interface, which is tightly bound to the adsorption of the *CO reaction intermediate and further promotes the C–C coupling process.

中文翻译：

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动态 Cu0/Cu+ 界面促进酸性 CO2 电还原


酸性CO ₂ 电还原反应（CO ₂ RR）显示出碳利用率高的优势，但在抑制不希望的析氢竞争和增加C ₂₊ 产物方面遇到了巨大挑战选择性。尽管已知Cu ⁰ /Cu ⁺ 界面有利于C-C耦合过程，但在强还原条件和大电流电解下，铜的氧化态不能得到很好的维持手术。在此，我们提出了一种 I ₂ 加成策略，以保护 Cu 的氧化态并促进酸性 CO ₂ /Cu ⁺ 界面 RR。通过在电解液中添加 I ₂ ，即使在 0.4–0.6 A cm ^–2 条件下，也能实现 70% 以上的高 C ₂₊ 产物法拉第效率在 0.3 M 的低 K ⁺ 浓度下，这与报道的 K ⁺ 浓度 (2-3 M) 几乎十倍的性能相当。电解质中的低 K ⁺ 浓度显着避免了 CO ₂ 传输通道中的盐结晶，从而增强了电解槽的稳定性。表面普贝图和实验结果证明，电解液中添加过量的I ₂ 会促进CuI的生成；此外，CuI 和金属 Cu 在电化学还原条件下共存，证明存在 Cu → CuI → Cu 的氧化还原回路。该环是构建动态Cu ⁰ /Cu ⁺ 界面的关键，该界面与*CO反应中间体的吸附紧密结合，进一步促进C-C偶联过程。