Ordered Bi ₂ S ₃ Framework Enabled Site‐Selective Bismuth Restructuring Toward Efficient CO ₂ Electroreduction to Formic Acid

Abstract The precise reconstruction of interfacial active sites remains challenging in disordered systems due to uncontrollable metallic phase growth and mass transport limitations. Here, an ordered three‐dimensional bismuth sulfide (Bi 2 S 3 ) nanorod scaffold is developed to enable spatially confined epitaxial growth of metallic Bismuth (Bi) at predetermined heterointerfaces. By synergizing nanoconfinement with controlled reduction, the directional epitaxial growth of highly active metallic Bi phases along Bi 2 S 3 nanorod interfaces is realized, simultaneously establishing order Bi/Bi 2 S 3 ( o ‐Bi/Bi 2 S 3 ) heterointerface arrays and sulfur vacancy‐enriched catalytic motifs. The optimized o ‐Bi/Bi 2 S 3 catalyst delivers exceptional CO 2 ‐to‐HCOOH conversion performance in 0.1 m KHCO 3 electrolyte, achieving a high Faradaic efficiency of 94.6% at −1.06 V versus RHE with a corresponding partial current density of 13.7 mA cm −2 , alongside 18 h operational stability. In situ attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) and density functional theory (DFT) demonstrate that the precisely grown Bi at the heterointerfaces reduces the energy barrier for * OCHO intermediate formation and effectively suppresses * H species generation. This work establishes a paradigm for topologically guided phase transformation of metallic elements at designer sites while mechanistically elucidating the structure‐performance interplay between ordered nanoarchitectures and heterointerface engineering in boosting CO 2 electroreduction kinetics.