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)显示出高碳利用效率的优势，但在抑制不期望的析氢竞争和提高C ₂₊产物选择性方面遇到巨大挑战。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操作下，铜的氧化态不能得到很好的维持。在此，我们提出了涉及I ₂加成的策略，以保护Cu的氧化态并促进酸性CO ₂ RR过程中的动态Cu ⁰ /Cu ⁺界面。通过在电解液中添加I ₂ ，即使在0.3 M的低K ^{+浓度下，也可以在0.4–0.6 A cm –2}下实现70%以上的高C ₂₊产物法拉第效率，这与报道的结果相当K ⁺浓度 (2–3 M)几乎高出十倍时的性能。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。该环路是构建动态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，并进一步促进C-C偶联过程。