Reconstruction of Bi₂S₃ in CO₂ Electroreduction via Topotactic Transformation

Bismuth-based catalysts have demonstrated significant electrocatalytic activity in the electrochemical CO 2 reduction reaction (CO 2 RR) to produce formate/formic acid, while the morphology of these catalysts is considered to be crucial for their electrocatalytic performance. However, the potential topological transformation of Bi-based catalysts during CO 2 RR catalysis has been largely overlooked, which could lead to an underlying lack of understanding of the structure–activity relationship. In this study, various morphologies of bismuth sulfide (Bi 2 S 3 ), including nanowires, nanoribbons, nanospheres, nanoparticles, and commercially available bulk powders of Bi 2 S 3, were systematically investigated for the electrocatalytic CO 2 RR in a 1 M KOH electrolyte. Surprisingly, all of these morphologies exhibit excellent electrocatalytic activities for formate synthesis, with high Faradaic efficiencies exceeding 90%. Meanwhile, no significant distinction could be observed regarding their catalytic performance during long-term operation. During the CO 2 RR process, all Bi 2 S 3 morphologies initially turn into similar nanocomposites of Bi and Bi 2 O 2 CO 3 sheets, which subsequently undergo a topotactic transformation into metallic Bi nanoparticles. Theoretical calculations indicate that such a topotactic transformation is conducive to the CO 2 RR due to the superior activity and selectivity of metallic Bi nanoparticles. These findings shed light on the impact of the topotactic transformation of bismuth-based catalysts on the CO 2 RR, providing insights into the structure–activity relationship.