In-situ morphology transformation of bismuth-based catalysts for effective electroreduction of carbon dioxide

Bismuth (Bi)-based catalysts have been widely used for the electroreduction of carbon dioxide (CO2). In this work, a Bi-based catalyst was electrodeposited on Cu foam substrate and applied for the selectively electrochemical reduction of CO2 to formic acid (HCOOH). An in-situ morphological transformation phenomenon accompanied by the formation of petal-shaped bismuth subcarbonate (Bi2O2CO3) nanosheets was observed to enhance the electrocatalytic performance. By using this catalyst, the faradaic efficiency of CO2 to HCOOH reached 92% at 1.6 V (vs Ag/AgCl) with a current density of 10 mA cm-2. Also, this electrocatalyst exhibited good stability during the electrocatalysis operation for 20 h. Density functional theory (DFT) calculations revealed that in-situ formed Bi2O2CO3 species can enhance the catalytic activity by stabilizing *OOCH intermediate through the stronger orbital hybridization of Bi 6p of Bi2O2CO3 with O 2p of *OOCH. As such, it can be considered that the rate-limiting step in the CO2 electroreduction process should rely on the second-step electron transfer, which is consistent with the Tafel slope analysis result.