Anionic Surfactant-Tuned\nInterfacial Water Reactivity\nPromoting Electrocatalytic CO<sub>2</sub> Reduction

The effects of the electrical double layer (EDL), which\npertain\nto the compositions and interactions among electrolyte species, significantly\nimpact the catalytic process. There is a pressing need to investigate\nthe role of electrolyte components and to deepen our understanding\nof EDL effects. In this study, we tune the water activity within a\nrange of anionic surfactants featuring different functional groups\nto adjust H<sub>2</sub> evolution activity and CO<sub>2</sub> reduction\nselectivity. We demonstrate that these anionic surfactants are active\nin the local reaction environment under a cathodic potential. The\nenhanced selectivity of CO<sub>2</sub> to CO can be attributed to\nthe robust interfacial hydrogen-bonding network reformed by the anionic\nsurfactants. This network diminishes the water dissociation activity\nand promotes the hydrogenation step in CO<sub>2</sub> reduction. Notably,\nthe electrolyte incorporating anionic surfactants improves the CO<sub>2</sub> reduction performance, registering CO Faradaic efficiencies\nof 89.7% (RSO<sub>3</sub><sup>–</sup>, SDS), 97.5% (RSO<sub>4</sub><sup>–</sup>, SLS), 98.4% (RPO<sub>4</sub><sup>2–</sup>, SMP), and 98.9% (RCOO<sup>–</sup>, SL) at −1.2 V\nversus RHE, thereby outperforming the blank KHCO<sub>3</sub> electrolyte\n(53.1%). This research underscores the crucial influence of anionic\nadditives in the CO<sub>2</sub>RR.