Active-site stabilized Bi metal–organic framework-based catalyst for highly active and selective electroreduction of CO2 to formate over a wide potential window

Abstract

Bismuth-based materials have been validated to be a kind of effective electrocatalyst for electrocatalytic CO₂ reduction (ECR) to formate (HCOO⁻). However, the established studies still encounter the problems of low current density, low selectivity, narrow potential window, and poor catalyst stability. Herein, a bismuth-terephthalate framework (Bi-BDC MOF) material was successfully synthesized. The optimized Bi-BDC-120 °C exhibited excellent activity, selectivity, and durability for formate production. At an operating potential of −1.1 V vs. RHE in 0.1 mol L⁻¹ KHCO₃ electrolyte, the ECR catalyzed by Bi-BDC-120 °C achieved a Faraday efficiency (FE) of 97.2% towards formate generation, and the total current density reached about 30 mA cm⁻². The operating potential window with FE_formate values > 95% ranged in −0.9 to −1.5 V vs. RHE. The density-functional theory (DFT) calculation demonstrated that the (001) crystalline planes of Bi-BDC are preferable for the adsorption of CO₂ and the conversion of *OCHO intermediates, thus ultimately promoting the electrocatalytic production of formate. Although the MOF structure of Bi-BDC-120 °C was insufficiently stabilized, the FE_formate could be maintained at around 90% after 36 h of ECR operation. The long-term durability for formate production was attributed to the fact that the in situ reconstructed Bi₂O₂CO₃ could retain the Bi–O active sites in the structure. These results offer an opportunity to design CO₂ reduction electrocatalysts with high activity and selectivity for potential applications.