Liquid-phase exfoliated ultrathin Bi nanosheets: Uncovering the origins of enhanced electrocatalytic CO₂ reduction on two-dimensional metal nanostructure

Electrochemical CO₂ reduction has been considered as a promising route for renewable energy storage and carbon-neutral energy cycle. However, the selectivity and stability of electrocatalysts for CO₂ reduction need to be improved. Two-dimensional (2D) layered electrocatalysts with high conductivity and abundant active sites have been considered as good candidates for CO₂ reduction. Herein, we propose a liquid-exfoliation strategy to prepare ultrathin 2D bismuth (Bi) nanosheets towards efficient electrocatalytic CO₂ conversion. Compared with bulk Bi, the increased edge sites on ultrathin Bi nanosheets played a vital role in CO₂ adsorption and reaction kinetics, significantly facilitating CO₂-to-formate (HCOOH/HCOO^-) conversion. Through density functional theory (DFT) calculation, we found that the *OCOH formation step tended to occur on edge sites rather than on facet sites, as confirmed by the lower Gibbs free energies. Benefited from the high conductivity and rich edge sites, Bi nanosheets exhibited a Faradaic efficiency of 86.0% for formate production and a high current density of 16.5 mA cm⁻² at − 1.1 V (vs. RHE), much superior to bulk Bi. Moreover, the Bi nanosheets could maintain well-preserved catalytic activity after long-term testing for over consecutive 10 h. We hope this study may provide new insights for the fabrication of novel 2D nanostructured metals for highly-efficient and long-life electrocatalytic CO₂ conversion.