Tuning Local CO ₂ Concentration via Controllable Wettability to Explore Multicarbon Product Selectivity in CO ₂ Electroreduction

The electrochemical conversion of CO₂ to multicarbon products is an enticing strategy for storing renewable electricity and producing valuable chemicals. However, the distinguished contributions from surface CO₂ concentration and local pH to the selective formation of multicarbon products are still ambiguous. Herein, by regulating the interfacial CO₂ transfer through tuning the surface wettability of the electrode, in situ fluorescence electrochemical spectroscopy combined with in situ Raman spectroscopy is employed to decouple the contributions from surface CO₂ concentration and local pH. In situ spectral results demonstrate that the superhydrophobic electrode surface maintains a high surface CO₂ concentration. However, the relatively sufficient buffer reaction driven by rapid CO₂ transfer retards the increase in local pH, which is unfavorable for promoting the formation of multicarbon products. Nonetheless, the superhydrophobic electrode achieves a multicarbon product selectivity of 66.5%, which is 1.93 times higher than that of the conventional Cu electrode. On the basis of these results, we further discuss the kinetic correlations between the microenvironment and multicarbon product selectivity. Operando Raman results showed that although the local pH of the superhydrophobic electrode is lower than that of the bare Cu electrode, more prominent peaks corresponding to Cu-CO and *CO_2^- are identified. This observation reveals that the high surface CO₂ concentration sustained by the superhydrophobic electrode enables rapid CO₂ activation and *CO formation, which then determines the formation of multicarbon products.