The availability of inexpensive industrial CO gas streams motivates efficient electrocatalytic upgrading of CO to higher-value feedstocks such as ethylene. However, the electrosynthesis of ethylene by the CO reduction reaction (CORR) has suffered from low selectivity and energy efficiency. Here we find that the recent strategy of increasing performance through use of highly alkaline electrolyte—which is very effective in CO₂RR—fails in CORR and drives the reaction to acetate. We then observe that ethylene selectivity increases when we constrain (decrease) CO availability. Using density functional theory, we show how CO coverage on copper influences the reaction pathways of ethylene versus oxygenate: lower CO coverage stabilizes the ethylene-relevant intermediates whereas higher CO coverage favours oxygenate formation. We then control local CO availability experimentally by tuning the CO concentration and reaction rate; we achieve ethylene Faradaic efficiencies of 72% and a partial current density of >800 mA cm⁻². The overall system provides a half-cell energy efficiency of 44% for ethylene production.

廉价的工业CO气流的可用性促使CO高效地电催化转化为高价值的原料，例如乙烯。但是，通过CO还原反应（CORR）进行的乙烯的电合成的选择性和能量效率低。在这里，我们发现通过使用高度碱性的电解质（在CO _2中非常有效）来提高性能的最新策略RR-CORR失效，并将反应驱动为乙酸盐。然后我们观察到，当我们限制（减少）CO的可用性时，乙烯的选择性会增加。使用密度泛函理论，我们展示了铜上的CO覆盖率如何影响乙烯与含氧化合物的反应途径：较低的CO覆盖率可稳定与乙烯相关的中间体，而较高的CO覆盖率则有利于含氧化合物的形成。然后，我们通过调整一氧化碳浓度和反应速率，通过实验控制局部一氧化碳的利用率。我们实现了72％的乙烯法拉第效率和> 800 mA cm ^-2的分电流密度。整个系统为乙烯生产提供了44％的半电池能效。