Tandem catalysts have demonstrated considerable potential for the electrocatalytic reduction of CO2 (CO2RR) to multicarbon (C2+) products by spatially decoupling CO generation and C–C coupling. However, achieving high selectivity toward a specific C2+ product remains challenging, primarily due to shared intermediates and insufficient understanding of the role of *CO coverage in steering product distribution. In this study, we design a molecular-bridged tandem catalyst with atomically precise Cu and Co sites, wherein the molecular bridge length fixes the intersite distance while the terminal ligands finely modulate the electronic structure of the Co center. This tailored architecture allows precise control over local *CO coverage and spillover, enabling systematic investigation of its influence on C–C coupling pathways. Fine-tuning *CO coverage enabled product distribution switching with the ratio of ethanol/ethylene changing from 3.2 to 0.6, reaching 68.4% ethanol and 63.1% ethylene among C2+ products. In situ spectroscopic analysis and density functional theory (DFT) calculations indicate that moderate *CO coverage weakens the carbon affinity on Cu, promoting carbon hydrogenation of *CHCO toward ethanol. In contrast, higher *CO coverage favors oxygen hydrogenation, leading to ethylene formation. The optimized catalyst, with 4-mercaptobenzonitrile bridged (Cu-L2-TPPCo), achieves a Faradaic efficiency of 53.2% for ethanol at −1.0 V vs RHE.
Wang et al. (Tue,) studied this question.