In situ transformation of a Bi-based MOF to a highly active catalyst for CO2 reduction

Abstract

Electrochemical carbon dioxide reduction reaction (ECO₂RR) is an effective means to promote carbon cycling. Recently, Bi-based metal–organic frameworks (MOFs) have attracted significant attention due to their high efficiency for formic acid generation in ECO₂RR, however, their composition and morphology transformation during electrocatalysis still lack a deep exploration. Herein, a Bi-MOF with 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (H₃TATB) ligand is used as the prototype to investigate its in situ transformation during ECO₂RR. With various characterization methods, the detailed transformation processes are revealed. Firstly, the Bi-MOF was transformed into Bi₂O₂CO₃ due to ligand substitution in KHCO₃ electrolyte, resulting in changes in both shape and composition. Secondly, during ECO₂RR, the Bi³⁺ ions can be reduced into metallic Bi⁰ nanoparticles and act as the real active component for ECO₂RR. The resultant catalyst exhibits a high selectivity of up to 94.3% towards formate generation. At an optimal potential of −1.08 V vs. RHE, the catalyst can maintain a current density of −25 mA cm⁻² and a faradaic efficiency of formate over 90% for 14.5 hours. This work not only develops an efficient electrocatalyst for ECO₂RR but also provides a new insight into the in situ reconstruction of MOF precursor into the active catalyst, which is useful for the design and synthesis of other materials.