Stabilizing Bi active species via constructing a Bi-O-Ce interface for enhanced CO₂ electroreduction to formate

The electrocatalytic reduction of CO₂ to formate is a key route for carbon resource recycling. Bismuth-based catalysts are widely studied for their high formate selectivity. However, at high current densities, rapid in situ over-reduction of Bi³⁺ often induces agglomeration of active species (Bi⁰), compromising structural stability, reducing active sites, and degrading catalytic performance. In this study, a CeO₂@BOC catalyst featuring a Bi-O-Ce composite interface was designed by incorporating CeO₂ into Bi₂O₂CO₃ (BOC). This catalyst achieves a formate faradaic efficiency (FE_formate) of 95.7% at -0.9 V vs. RHE in an H-cell. Moreover, in a flow cell, it maintains a current density of 225 mA cm^-2 over 120 hours at the same potential, with FE_formate consistently above 90%. Characterization results demonstrate that the high catalytic performance of the catalyst originates from the stabilization of active species by the Bi-O-Ce interface. This strategy of tuning the reduction behavior of bismuth species and inhibiting the aggregation of active species offers new insights for developing efficient and stable CO₂ electroreduction to formate processes.