Electrochemical CO reduction can serve as a sequential step in the transformation of CO₂ into multicarbon fuels and chemicals. In this study, we provide insights on how to steer selectivity for CO reduction almost exclusively toward a single multicarbon oxygenate by carefully controlling the catalyst composition and its surrounding reaction conditions. Under alkaline reaction conditions, we demonstrate that planar CuAg electrodes can reduce CO to acetaldehyde with over 50% Faradaic efficiency and over 90% selectivity on a carbon basis at a modest electrode potential of −0.536 V vs. the reversible hydrogen electrode. The Faradaic efficiency to acetaldehyde was further enhanced to 70% by increasing the roughness factor of the CuAg electrode. Density functional theory calculations indicate that Ag ad-atoms on Cu weaken the binding energy of the reduced acetaldehyde intermediate and inhibit its further reduction to ethanol, demonstrating that the improved selectivity to acetaldehyde is due to the electronic effect from Ag incorporation. These findings will aid in the design of catalysts that are able to guide complex reaction networks and achieve high selectivity for the desired product.

电化学还原CO可作为转化CO ₂的顺序步骤进入多碳燃料和化学品。在这项研究中，我们提供了有关如何通过仔细控制催化剂组成及其周围的反应条件，如何几乎完全将二氧化碳还原选择性转向单一的多碳氧化物的见解。在碱性反应条件下，我们证明，相对于可逆氢电极，平面CuAg电极可在-0.536 V的中等电势下，以碳为基础，以超过50％的法拉第效率和超过90％的选择性将CO还原为乙醛。通过增加CuAg电极的粗糙度系数，将法拉第对乙醛的效率进一步提高到70％。密度泛函理论计算表明，Cu上的Ag原子削弱了还原的乙醛中间体的结合能并抑制了其进一步还原为乙醇，表明对乙醛的选择性提高是由于掺入银的电子效应。这些发现将有助于催化剂的设计，该催化剂能够引导复杂的反应网络并实现所需产物的高选择性。