One-pot synthesis of surfactant-intercalated tin(IV) disulfide nanosheets heterojuncted with bismuth(III) sulfide needles for efficient conversion carbon dioxide into formate.

Electrocatalytic conversion of carbon dioxide (CO2) to formate is an effective strategy for converting CO2 into valuable chemicals. However, synthesizing active catalysts with well-defined heterojunctions and large exposed surfaces remains challenging. Here, we present a one-pot synthesis method for a hybrid sulfide catalyst featuring surfactant-intercalated tin(IV) disulfide (SnS2) nanosheets heterojuncted with bismuth(III) sulfide (Bi2S3) needles. The surfactant hexadecyltrimethylammonium bromide (CTAB) plays a vital role in transforming the morphology of the components and the formation of their heterojunction. The resulting catalyst exhibits outstanding performance in reducing CO2 to formate, demonstrating the high formate Faradaic efficiency (FE) of over 90 % across a wide potential range from -0.8 to -1.3 V (vs. reversible hydrogen electrode (RHE)) and achieving a maximum FEformate of 97.2 % at -1.1 V (vs. RHE). In contrast, the partial current density of formate reaches about 350 mA cm-2 at -1.35 V (vs. RHE) in the flow cell. Furthermore, the catalyst demonstrated exceptional stability, with a high selectivity towards formate production maintained at a current density of 156 mA cm-2. Theoretical calculations and in situ Raman indicate that the SnS2/Bi2S3 heterojunction active sites optimize the free energy for the *H and *OCHO intermediates, thereby facilitating the formation and desorption steps of *HCOOH, ultimately leading to formate yield efficiently. Our investigation offers a strategic method and valuable insights for designing catalytic materials with rich interfaces for efficient CO2 reduction reactions.