Dynamic (Sub)surface‐Oxygen Enables Highly Efficient Carbonyl‐Coupling for Electrochemical Carbon Dioxide Reduction
You‐Chiuan Chu, Kuan‐Hsu Chen, Ching‐Wei Tung, Hsiao‐Chien Chen, Hsiao‐Chien Chen, Jiali Wang, Tsung‐Rong Kuo, Tsung‐Rong Kuo, Chia‐Shuo Hsu, Kuo‐Hsin Lin, Li Duan Tsai, Hao Ming Chen, Hao Ming Chen
Abstract
Abstract Nowadays, high‐valent Cu species (i.e., Cu δ + ) are clarified to enhance multi‐carbon production in electrochemical CO 2 reduction reaction (CO 2 RR). Nonetheless, the inconsistent average Cu valence states are reported to significantly govern the product profile of CO 2 RR, 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 CO 2 RR 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 CO 2 RR. 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 Cu 2 O@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.