Anionic Surfactant-Tuned Interfacial Water Reactivity Promoting Electrocatalytic CO₂ Reduction

The effects of the electrical double layer (EDL), which pertain to the compositions and interactions among electrolyte species, significantly impact the catalytic process. There is a pressing need to investigate the role of electrolyte components and to deepen our understanding of EDL effects. In this study, we tune the water activity within a range of anionic surfactants featuring different functional groups to adjust H2 evolution activity and CO2 reduction selectivity. We demonstrate that these anionic surfactants are active in the local reaction environment under a cathodic potential. The enhanced selectivity of CO2 to CO can be attributed to the robust interfacial hydrogen-bonding network reformed by the anionic surfactants. This network diminishes the water dissociation activity and promotes the hydrogenation step in CO2 reduction. Notably, the electrolyte incorporating anionic surfactants improves the CO2 reduction performance, registering CO Faradaic efficiencies of 89.7% (RSO3–, SDS), 97.5% (RSO4–, SLS), 98.4% (RPO42–, SMP), and 98.9% (RCOO–, SL) at −1.2 V versus RHE, thereby outperforming the blank KHCO3 electrolyte (53.1%). This research underscores the crucial influence of anionic additives in the CO2RR.