In situ structural evolution of BiOCOOH nanowires and their performance towards electrocatalytic CO₂ reduction

Bismuth-based materials have attracted broad research interest as catalysts for electrocatalytic CO₂ reduction (ECR) to formate in recent years. Most studies have been focused on exploring materials with high activity, selectivity, and durability, while little attention has been paid to the catalysts structure stability especially under working conditions of CO₂ electrolysis. Here, starting from the precursor of bismuth oxide formate nanowires (BiOCOOH NWs), it was found that BiOCOOH NWs were easy to electrochemically evolve into two-dimensional sheet structure in CO₂-saturated KHCO₃ solution and would further reconstitute into larger ultrathin bismuth nanosheets covered with amorphous oxide thin layer (Bi/BiO_x NSs). However, in Ar-saturated HCOONa solution, the one-dimensional structure could be maintained and reconstructed into rough porous bismuth nanowires (Bi NWs). Bi NWs showed less stability during ECR, which also generated surface amorphous oxide layer and further fragmentated into nanoparticles or nanosheets. Bi/BiO_x NSs showed better activity, selectivity, and stability than Bi NWs, thanks to the high exposing active sites, enhancing CO₂ adsorption and charge transfer. The demonstrated electrolyte dependence of structure evolution for bismuth-based catalysts and their performance for CO₂ electroreduction could provide guidance for the design and synthesis of efficient catalysts.