Lattice Strain and Electron Modulation in Bimetallic Bi–Sb Catalysts for Enhanced CO ₂ Electroreduction to Formate

The electrochemical reduction of CO₂ to valuable chemicals and fuels using bismuth-based catalysts offers a promising pathway toward achieving carbon neutrality. It is widely acknowledged that lattice strain significantly influences the catalytic performance of electrocatalysts in the CO₂ reduction reaction (CO₂RR). Nevertheless, research dedicated to lattice strain engineering in Bi-based catalysts, particularly through the introduction of similar elements from the same group, remains limited. In this work, we rationally designed a bimetallic Bi-Sb catalyst by incorporating Sb into the Bi lattice to induce controlled lattice strain and electronic effects. The optimized Bi₉₉Sb₁ catalyst achieved a peak formate Faradaic efficiency (FE) of 99.4% in a flow cell, maintained FEs above 94.8% over a broad potential window (-0.6 to -1.1 V vs. RHE), and exhibited the highest intrinsic activity. In situ characterizations and density functional theory calculations revealed that Sb doping introduced localized lattice strain while modulating the electronic structure of adjacent Bi sites, thereby strengthening CO₂ adsorption and activation on Bi active centers, reducing the energy barrier for forming the critical *OCHO intermediate. This work highlights the effectiveness of incorporating neighboring metals to tailor lattice strain in Bi-based electrocatalysts, providing a feasible strategy to enhance the catalytic performance of Bi-based electrocatalysts.