Redistributing the local electron density of bismuth via introducing halogen atoms for boosting CO₂ reduction to formate

Bi-based materials have great potential for facilitating CO₂ electrochemical reduction (CO₂RR) to formate. Herein, guided by theoretical calculations, we constructed a metallic Bi electrocatalyst with Cl doped into its surface layer (Bi-Cl). The local electron density of Bi was redistributed, and the electrophilic Bi sites were also formed due to the relatively high electronegativity difference between Bi and Cl. Benefitting from this, a high formate Faradaic efficiency (94.5%) with a partial current density of ∼ −1.4 A cm⁻² and a record formate formation rate of 25.7 μmol cm⁻² h⁻¹ at −0.86 V versus reversible hydrogen electrode, along with good long-term stability for more than 180 h at −400 mA cm⁻² and 10 h at −10 A, can be achieved. Theoretical and experimental explorations verified that the enhanced capacities of inert CO₂ activation and H₂O dissociation contributed to the high CO₂RR performance in Bi-Cl.