Engineering Ultrathin Bismuth Nanosheets With Active Facet for Highly Efficient CO₂ Electroreduction to Formate

Bismuth-based electrocatalysts have shown great promise for the electrochemical reduction of CO₂ to formate. However, taming the active crystal facets to realize high selectivity and long-term stability remains a fundamental challenge. Herein, we describe a facile one-step electrodeposition strategy that enables the bismuth nanosheets to dominantly expose the (110) facet via deposition potential modulation. Particularly, the bismuth catalyst structure undergoes in operando reconstruction, in which the highly active (110) facet appears and is well maintained during the electrolysis owing to the reduction from Bi³⁺ to metallic Bi⁰. Therefore, the bismuth catalyst with ultrathin nanosheets exhibits high catalytic activity and long-term durability, achieving over 90% Faradaic efficiency for formate over a wide potential range from -0.7 to -1.3 V_RHE. When assembled in a Zn-CO₂ battery, the bismuth-based cathode catalyst also demonstrates stable cycling, further confirming the robust durability of the (110)-facet-stabilized catalyst under operating conditions. Mechanistic studies reveal that the (110) facet facilitates the CO₂ activation process and stabilizes the critical *OCHO intermediate, thereby promoting the reaction pathway selectively toward formate formation while suppressing the competitive hydrogen evolution reaction. This work establishes a facet-engineering strategy via a facial electrochemical synthesis as the accessible route for designing high-performance CO₂ reduction reaction catalysts.