In‐Situ Observation of Post‐CO Intermediates to Decode C–C Coupling Pathways in CO2 Electroreduction

Electrocatalytic carbon dioxide (CO2) reduction reaction (CO2RR) has emerged as a promising strategy for sustainable energy conversion and carbon utilization. Despite intensive research efforts, the understanding of intermediates and pathways from CO2RR to multicarbon (C2+) chemicals remains incomplete. The challenge is to gain insight into the activation of adsorbed CO and the subsequent pathways. Here, we design a specially tailored Cu nanowire array facing a hydrophobic interface as an electrode to highly enhance Raman signals in the in‐situ environment, allowing sensitive observation of the sequential change of various elusive intermediates during CO2RR, such as CO, CH2, CO coexisting with CH2, CH2CO, and CH3. Density functional theory calculations reveal that the C–C coupling during CO2RR originates from an asymmetric coupling between CH2 and CO to form CH2CO, identified as the rate‐determining step in the formation of C2+ products formation. These results deepen the understanding of the C–C coupling processes, which is crucial for advancing catalyst development in electrochemical CO2 upgrading.