The conversion of carbon dioxide to value-added products using renewable electricity would potentially help to address current climate concerns. The electrochemical reduction of carbon dioxide to propylene, a critical feedstock, requires multiple C–C coupling steps with the transfer of 18 electrons per propylene molecule, and hence is kinetically sluggish. Here we present the electrosynthesis of propylene from carbon dioxide on copper nanocrystals with a peak geometric current density of −5.5 mA cm⁻². The metallic copper nanocrystals formed from CuCl precursor present preponderant Cu(100) and Cu(111) facets, likely to favour the adsorption of key *C₁ and *C₂ intermediates. Strikingly, the production rate of propylene drops substantially when carbon monoxide is used as the reactant. From the electrochemical reduction of isotope-labelled carbon dioxide mixed with carbon monoxide, we infer that the key step for propylene formation is probably the coupling between adsorbed/molecular carbon dioxide or carboxyl with the *C₂ intermediates that are involved in the ethylene pathway.

使用可再生电力将二氧化碳转化为增值产品可能有助于解决当前的气候问题。将二氧化碳电化学还原为丙烯（一种关键原料）需要多个 C-C 偶联步骤，每个丙烯分子转移 18 个电子，因此在动力学上是缓慢的。在这里，我们展示了在铜纳米晶体上从二氧化碳电合成丙烯，峰值几何电流密度为 -5.5 mA cm ^-2。_{由 CuCl 前体形成的金属铜纳米晶体呈现出占优势的 Cu(100) 和 Cu(111) 面，可能有利于关键的 *C 1}和 *C ₂的吸附中间体。引人注目的是，当使用一氧化碳作为反应物时，丙烯的生产率大幅下降。从同位素标记的二氧化碳与一氧化碳混合的电化学还原，我们推断丙烯形成的关键步骤可能是吸附/分子二氧化碳或羧基与参与乙烯途径的*C 2 中间体之间的偶联_。