The electrochemical CO₂ reduction reaction on Cu is widely believed to occur via two consecutive and orthogonal reaction steps, that is, CO₂-to-CO and CO-to-C₂₊, on the same sites. Here we provide compelling experimental evidence that challenges these long-held assumptions. We show that the presence of CO₂ promotes the electrochemical CO reduction reaction, and there are at least two distinct types of Cu sites, with one (Cu_CO2) more active in the CO₂-to-CO conversion and the other (Cu_CO) favouring the further reduction of CO to C₂₊ products. CO adsorbed on Cu_CO is at least six times more active towards the formation of C₂₊ products than that on Cu_CO2. Isotopic labelling experiments on Cu(111) and Cu(100) surfaces indicate that Cu_CO2 and Cu_CO probably correspond to Cu(111)-like and defect sites, respectively. These insights highlight the possibility of selectivity control in the CO₂ reduction reaction.

人们普遍认为Cu上的电化学CO ₂还原反应是通过两个连续且正交的反应步骤发生的，即在同一位点上的CO ₂ -to-CO和CO-to-C _{2+ 。}在这里，我们提供了令人信服的实验证据来挑战这些长期持有的假设。_{我们发现CO 2}的存在促进了电化学CO 还原反应，并且至少有两种不同类型的Cu 位点，其中一种(Cu _CO2 ) 在CO ₂ -to-CO 转化中更活跃，另一种(Cu _CO）有利于CO进一步还原为C ₂₊产品。CO 吸附在 Cu _CO上形成 C ₂₊产物的活性至少是 Cu _CO2的六倍。Cu(111) 和 Cu(100) 表面的同位素标记实验表明 Cu _CO2和 Cu _CO可能分别对应于类 Cu(111) 和缺陷位点。_{这些见解强调了CO 2}还原反应中选择性控制的可能性。