Facile CO2 Electro-Reduction to Formate via Oxygen Bidentate Intermediate Stabilized by High-Index Planes of Bi Dendrite Catalyst

Electrochemical CO2 conversion to chemical products is a promising strategy for sustainable industrial development. However, the success of this approach requires an in-depth understanding of catalysis because it involves highly complex multistep reactions. Herein, we suggest a rational design of a hierarchical Bi dendrite catalyst for an efficient conversion of CO2 to formate. A high selectivity (similar to 89% at -0.74 V-RHE)and, more importantly, a stable performance during long-term operation (similar to 12 h) were achieved with the Bi dendrite. Density functional theory (DFT) is used to investigate three possible reaction pathways in terms of surface intermediate, and the one via *OCOH surface intermediate is calculated to be the most energetically feasible. DFT calculations further elucidate the plane-dependent catalytic activity and conclude that the high-index planes developed on the Bi dendrite are responsible for the sustainable performance of Bi dendrite. We expect that our experimental and theoretical study will provide a fundamental guideline for the CO2-to-formate conversion pathway as well as design principles for enhancing the catalytic performance.