Sulfur Doping Induces Interfacial Water Regulation on Bi-Based Catalysts for Efficient Electrochemical CO₂ Reduction...

Electrochemical CO₂ reduction (CO₂RR) to formate is one of the green routes for achieving high-value conversion of CO₂. However, the reaction performance is limited by difficult CO₂ activation and sluggish water dissociation. Herein, sulfur-doped bismuth nanorods (BiS_x NR) are synthesized via a hydrothermal method combined with electrochemical reconstruction, which significantly enhances the catalytic activity and selectivity. In an H-type cell, BiS_x NR achieves a formate Faradaic efficiency ( ${\mathrm{FE}}_{{\mathrm{HCOO}}^{-}}$ ) of 95% at -1.15 V vs. RHE. In a flow cell, a ${\mathrm{FE}}_{{\mathrm{HCOO}}^{-}}$ exceeding 90% is stably maintained for 60 h at 200 mA cm^-2. A series of in situ and ex situ electrochemical characterizations reveal that sulfur species serve as anchoring sites to enrich K⁺(H₂O)_n hydrated clusters in the electrical double layer, optimizing interfacial water activation and proton transfer while suppressing the competing hydrogen evolution reaction. Moreover, sulfur doping modulates the electronic structure of bismuth active sites, enhancing CO₂ adsorption and stabilizing the key *OCHO intermediate. This work unveils the synergistic effect of interfacial water regulation and electronic effects in boosting CO₂RR performance, providing new insights for designing high-performance electrocatalysts via interface engineering.