Boosting the C–C Coupling Efficiency for Diluted CO₂ Electroreduction to Dual Carbon Products

Direct reduction of low–concentration CO2 in flue gas to multicarbon products has attracted increasing attention recently since it could reduce the high energy consumption of CO2 purification during CO2 recycling. Although various electrodes have been developed to convert diluted CO2 to different products, the changes in mechanisms due to the reduction of the CO2 concentration have rarely been studied. In this work, defective boron-modified copper electrodes were obtained for the direct conversion of diluted CO2 to dual carbon (C2) products. The Faradaic efficiency of C2 reached as high as 54.9%, even when the CO2 concentration was reduced to 25%. More importantly, the C–C coupling efficiency of *CO intermediates reached up to 79.3% under the condition of 25% CO2. This was attributed to the fact that a small amount of CO2 did not fully occupy all of the active sites at the beginning, which provided possible reaction space for the subsequent coupling and protonation reaction processes. Through in situ monitoring of different reaction intermediates under the conditions of different CO2 concentrations using in situ FT–IR, it is found that decreasing CO2 concentration did not alter the reaction pathway but influenced the conversion rate of key intermediates, which resulted in a change of product selectivity.