Reconstruction of Bi2S3 in CO2 Electroreduction via Topotactic Transformation

Bismuth-based catalysts have demonstrated significant electrocatalytic activity in the electrochemical CO2 reduction reaction (CO2RR) 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 CO2RR 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 (Bi2S3), including nanowires, nanoribbons, nanospheres, nanoparticles, and commercially available bulk powders of Bi2S3, were systematically investigated for the electrocatalytic CO2RR 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 CO2RR process, all Bi2S3 morphologies initially turn into similar nanocomposites of Bi and Bi2O2CO3 sheets, which subsequently undergo a topotactic transformation into metallic Bi nanoparticles. Theoretical calculations indicate that such a topotactic transformation is conducive to the CO2RR 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 CO2RR, providing insights into the structure–activity relationship.