CuBi nanosheets from in-situ topotactic transformation for efficient electrocatalytic CO2 reduction to formate

The electrochemical reduction of CO 2 (CO 2 RR) to formate is a promising strategy for carbon utilization and renewable energy storage. Herein, we develop a Cu 3 Bi 7 bimetallic nanosheet catalyst via an in situ topotactic transformation of BiOBr-CuBr heterojunctions. The resulting Cu 3 Bi 7 nanosheets feature abundant edge-active sites, enhanced electron transfer kinetics, and improved CO 2 adsorption, collectively boosting catalytic performance. Structural characterization confirms the coexistence of Cu and Bi phases in Cu 3 Bi 7 nanosheet, with strong electronic interactions optimizing the electronic structure, and mechanistic analysis indicates that the bimetallic synergy enhances CO 2 activation and stabilizes key intermediates, leading to superior selectivity and reaction kinetics. Electrochemical studies demonstrate that Cu 3 Bi 7 achieves a high formate Faradaic efficiency of 90 % at a current density of 120 mA cm -2 in a flow cell, maintaining exceptional stability for 90 h without performance degradation. This work provides a scalable strategy for designing efficient CuBi bimetallic catalysts and advances the development of CO 2 RR technology for practical applications.