Isolated ultrasmall Bi nanosheets for efficient CO₂-to-formate electroreduction

Electrochemical reduction of CO₂ to valuable formate as liquid fuel is a promising way to alleviate the greenhouse effect. The edge active sites in bismuth (Bi) nanosheets play a critical role in the electrochemical reduction of CO₂ into formate, which enable the operation of CO₂ reduction with high cathodic energy efficiency, especially under large current densities of ≥ 200 mA/cm². However, the undesirable reconstruction of small Bi nanosheets into large nanosheets leads to the decreasing of edge active sites during electrocatalysis. Here we report stable isolated ultrasmall bismuth nanosheets-synthesized by in-situ electrochemical transformation of ligands covered bismuth vanadate-on silver nanowires as an efficient electrocatalyst for CO₂-to-formate reduction. The cooperative electrocatalyst achieves a formate current density of 186 mA/cm² and a cathodic energy efficiency of 75% for formate, which is the only best compared to the literature results. Operando Raman and morphologic measurements demonstrate that the excellent energy utilization of the electrocatalyst is originated from the rich edge active sites with Bi-O species of the ultrasmall Bi nanosheets.