High-efficient carbon dioxide-to-formate conversion on Bi5O7NO3 by tuning the exposure of crystal plane during reconstruction in electrolysis

Abstract

The electrochemical conversion of carbon dioxide into formic acid offers an effective approach for utilizing carbon dioxide resources. Bismuth (Bi)-based catalysts have garnered significant attention in this field. However, designing high-performance Bi-based catalysts is challenging due to difficulties in accurately adjusting the reconstruction of such catalysts during electrolysis. In this study, we reported that nitrate ions positively influence the reconstruction of Bi5O7NO3 (BON), thereby outperforming Bi2O3 during ECO2RR. BON attained a Faraday efficiency of formate (FEHCOOH) and partial current density of 95.3 % and 25.1 mA/cm2 at −0.9 V vs RHE, respectively, surpassing the performance of Bi2O3 (90.2 % and 15.4 mA/cm2). The layered structure of BON mitigates Bi agglomeration during electrolysis, thus providing a large number of active sites. The presence of nitrate ions promotes exposure to abundant Bi(110) and Bi(015), whereas only the Bi(012) plane forms in Bi2O3 during electrolysis. In-situ ATR FTIR results indicate that both BON and Bi2O3 follow the same pathway for formate formation. Nevertheless, the high-index planes (015) cause the Bi derived from BON to remain in an electron defect state, which increases the adsorption of *CO2. In addition, Bi(110) plane has effectively lower the energy barriers for *OCHO production than Bi(012) plane. The Bi(015) and Bi(110) planes enhance the adsorption of *CO2 intermediates and reduce the energy barrier for *OCHO formation, respectively, which contributes to the improved ECO2RR activity of BON.