Dynamic Cu<sup>0</sup>/Cu<sup>+</sup> Interface Promotes Acidic CO<sub>2</sub> Electroreduction
Yunling Jiang, Haobo Li, Chaojie Chen, Yao Zheng, Shi‐Zhang Qiao
Abstract
Acidic CO 2 electroreduction reaction (CO 2 RR) shows advantages in high carbon utilization efficiency yet encounters great challenges in suppressing undesired hydrogen evolution competition and increasing C 2+ product selectivity. Although it is known that Cu 0 /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 I 2 addition involved strategy to protect the oxidation state of Cu and promote dynamic Cu 0 /Cu + interfaces during acidic CO 2 RR. With the addition of I 2 in the electrolyte, a high C 2+ 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 CO 2 transport channel to enhance the electrolyzer’s stability. As proved by the surface Pourbaix diagram and experimental results, adding excessive I 2 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 Cu 0 /Cu + interface, which is tightly bound to the adsorption of the *CO reaction intermediate and further promotes the C–C coupling process.