Nowadays, high-valent Cu species (i.e., Cu^δ+) are clarified to enhance multi-carbon production in electrochemical CO₂ reduction reaction (CO₂RR). Nonetheless, the inconsistent average Cu valence states are reported to significantly govern the product profile of CO₂RR, which may lead to misunderstanding of the enhanced mechanism for multi-carbon production and results in ambiguous roles of high-valent Cu species. Dynamic Cu^δ+ during CO₂RR leads to erratic valence states and challenges of high-valent species determination. Herein, an alternative descriptor of (sub)surface oxygen, the (sub)surface-oxygenated degree (κ), is proposed to quantify the active high-valent Cu species on the (sub)surface, which regulates the multi-carbon production of CO₂RR. The κ validates a strong correlation to the carbonyl (*CO) coupling efficiency and is the critical factor for the multi-carbon enhancement, in which an optimized Cu₂O@Pd_2.31 achieves the multi-carbon partial current density of ≈330 mA cm⁻² with a faradaic efficiency of 83.5%. This work shows a promising way to unveil the role of high-valent species and further achieve carbon neutralization.

中文翻译：

---

动态（亚）表面氧可实现高效羰基偶联，从而实现电化学二氧化碳还原

如今，高价Cu物种（即Cuδ ^{+）被澄清以增强电化学CO} ₂还原反应（CO ₂ RR）中的多碳生产。尽管如此，据报道，不一致的平均Cu价态显着控制CO ₂ RR的产物谱，这可能导致对多碳生产的增强机制的误解，并导致高价Cu物种的作用不明确。CO ₂ RR 过程中的动态 Cu ^{δ +}导致不稳定的价态和高价物种测定的挑战。在此，提出了（亚）表面氧的替代描述符，即（亚）表面氧化度（κ）来量化（亚）表面上的活性高价铜物种，其调节了多碳的产生CO ₂ RR。 κ验证了与羰基(*CO)耦合效率的强相关性，并且是多碳增强的关键因素，其中优化的Cu ₂ O@Pd _2.31实现了约330 mA cm的多碳部分电流密度⁻²，法拉第效率为 83.5%。这项工作展示了一种揭示高价物质的作用并进一步实现碳中和的有前途的方法。