Electric-field promoted C–C coupling over Cu nanoneedles for CO2 electroreduction to C2 products

Cu-based catalysts are the most promising candidates for electrochemical CO2 reduction (CO2RR) to multi-carbon (C2) products. Optimizing the C–C coupling process, the rate-determining step for C2 product generation, is an important strategy to improve the production and selectivity of the C2 products. In this study, we determined that the local electric field can promote the C–C coupling reaction and enhance CO2 electroreduction to C2 products. First, finite-element simulations indicated that the high curvature of the Cu nanoneedles results in a large local electric field on their tips. Density functional theory (DFT) calculations proved that a large electric field can promote C–C coupling. Motivated by this prediction, we prepared a series of Cu catalysts with different curvatures. The Cu nanoneedles (NNs) exhibited the largest number of curvatures, followed by the Cu nanorods (NRs), and Cu nanoparticles (NPs). The Cu NNs contained the highest concentration of adsorbed K+, which resulted in the highest local electric field on the needles. CO adsorption sensor tests indicated that the Cu NNs exhibited the strongest CO adsorption ability, and in-situ Fourier-transform infrared spectroscopy (FTIR) showed the strongest *COCO and *CO signals for the Cu NNs. These experimental results demonstrate that high-curvature nanoneedles can induce a large local electric field, thus promoting C–C coupling. As a result, the Cu NNs show a maximum FEC2 of 44% for CO2RR at a low potential (−0.6 V vs. RHE), which is approximately 2.2 times that of the Cu NPs. This work provides an effective strategy for enhancing the production of multi-carbon products during CO2RR.