Electrolyte alkaline cations can significantly modulate the reaction selectivity of electrochemical CO₂ reduction (eCO₂R), enhancing the yield of the valuable multicarbon (C₂₊) chemical feedstocks. However, the mechanism underlying this cation effect on the C–C coupling remains unclear. Herein, by performing constant-potential AIMD simulations, we studied the dynamic behavior of interfacial K⁺ ions over Cu surfaces during C–C coupling and the origin of the cation effect. We showed that the specific adsorption of K⁺ readily occurs at the surface sites adjacent to the *CO intermediates on the Cu surfaces. Furthermore, this specific adsorption of K⁺ during *CO–*CO coupling is more important than quasi-specific adsorption for enhancing coupling kinetics, reducing the coupling barriers by approximately 0.20 eV. Electronic structure analysis revealed that charge redistribution occurs between the specifically adsorbed K⁺, *CO, and Cu sites, and this can account for the reduced barriers. In addition, we identified excellent *CO–*CO coupling selectivity on Cu(100) with K⁺ ions. Experimental results show that suppressing surface K⁺-specific adsorption using the surfactant cetyltrimethylammonium bromide (CTAB) significantly decreases the Faradaic efficiency for C₂ products from 41.1% to 4.3%, consistent with our computational findings. This study provides crucial insights for improving the selectivity toward C₂₊ products by rationally tuning interfacial cation adsorption during eCO₂R. Specifically, C–C coupling can be enhanced by promoting K⁺-specific adsorption, for example, by confining K⁺ within a coated layer or using pulsed negative potentials.

中文翻译：

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碱性阳离子的特异性吸附增强了 CO2 电还原中的 CO-CO 偶联


电解质碱性阳离子可以显着调节电化学 CO₂ 还原 （eCO₂R） 的反应选择性，从而提高有价值的多碳 （C₂₊） 化学原料的产量。然而，这种阳离子效应对 C-C 偶联的潜在机制仍不清楚。在此，通过进行恒定电位 AIMD 模拟，我们研究了 C-C 耦合过程中界面 K⁺ 离子在 Cu 表面上的动态行为以及阳离子效应的起源。我们表明，K⁺ 的特异性吸附很容易发生在 Cu 表面上与 *CO 中间体相邻的表面位点。此外，在 *CO–*CO 耦合过程中 K⁺ 的这种特异性吸附对于增强耦合动力学来说比准特异性吸附更重要，将耦合势垒减少约 0.20 eV。电子结构分析表明，电荷重新分布在特异性吸附的 K⁺、*CO 和 Cu 位点之间，这可以解释势垒减少的原因。此外，我们还确定了对 Cu（100） 与 K⁺ 离子的出色 *CO–*CO 偶联选择性。实验结果表明，使用表面活性剂十六烷基三甲基溴化铵 （CTAB） 抑制表面 K⁺ 特异性吸附可将 C₂ 产物的法拉第效率从 41.1% 降低到 4.3%，这与我们的计算结果一致。本研究通过合理调节 eCO₂R 过程中的界面阳离子吸附，为提高对 C₂₊ 产物的选择性提供了重要见解。 具体来说，可以通过促进 K⁺ 特异性吸附来增强 C-C 耦合，例如，通过将 K⁺ 限制在涂层内或使用脉冲负电位。