The in situ morphology transformation of bismuth-based catalysts for the 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 a Cu foam substrate and applied to the selective 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, and this resulted in enhanced electrocatalytic performance. By using this catalyst, the faradaic efficiency of the CO2 to HCOOH process reached 92% at −1.6 V (vs. Ag/AgCl, −1.0 V vs. RHE) with a total current density of 10 mA cm−2. Also, this electrocatalyst exhibited good stability during electrocatalysis for 20 h. Density functional theory calculations revealed that in situ-formed Bi2O2CO3 species enhanced the catalytic activity by stabilizing the *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 be the second electron transfer step, which is consistent with the Tafel slope analysis results.