C–C coupling is a critical step of CO₂ fixation in constructing the carbon skeleton of value-added multicarbon products. The Wood–Ljungdahl pathway is an efficient natural process through which microbes transform CO₂ into methyl and carbonyl groups and subsequently couple them together. This asymmetric coupling mechanism remains largely unexplored in inorganic CO₂ electroreduction. Here we experimentally validate the asymmetric coupling pathway through isotope-labelled co-reduction experiments on a Cu surface where ¹³CH₃I and ¹²CO are co-fed externally as the methyl and the carbonyl source, respectively. Isotope-labelled multicarbon oxygenates were detected, which confirms an electrocatalytic asymmetric coupling on the Cu surface. We further employed tandem Cu–Ag nanoparticle systems in which *CH_x and *CO intermediates can be generated to achieve asymmetric C–C coupling for a practical CO₂ electroreduction. We found that the production of multicarbon oxygenates is correlated with the generation rate of two intermediate indicators, CH₄ and CO. By aligning their rates, the oxygenates generation rate can be maximized.

C-C偶联是CO ₂固定在构建增值多碳产品碳骨架中的关键步骤。Wood-Ljungdahl 途径是一种有效的自然过程，微生物通过该途径将 CO ₂转化为甲基和羰基，然后将它们偶联在一起。_{这种不对称的耦合机制在无机CO 2}电还原中很大程度上仍未被探索。在这里，我们通过在¹³ CH ₃ I 和¹²CO 分别作为甲基和羰基源从外部共同进料。检测到同位素标记的多碳氧化物，这证实了铜表面上的电催化不对称耦合。我们进一步采用了串联的 Cu-Ag 纳米粒子系统，其中可以生成*CH _{x和 *CO 中间体以实现不对称 C-C 耦合，从而实现实际的 CO 2}电还原。我们发现多碳含氧化合物的产生与两个中间指标 CH ₄和 CO 的生成速率相关。通过调整它们的速率，可以最大化含氧化合物的生成速率。