Dynamic structural evolution and active site identification of bismuth-based catalysts for electrochemical CO₂ reduction

Bismuth (Bi)-based catalysts have been gaining recognition as the most promising catalyst materials for the electrochemical CO₂ reduction reaction (eCO₂RR) to produce formate, which provides a potential way to solve the energy crisis and the global climate crisis. However, the dynamic structural evolution of catalysts is usually observed during the operando conditions, resulting in the great difficulties for the identification of intrinsic active sites and the revelation of the structure-activity relationship at the atomic scale. This significantly hinders the development of new-type Bi-catalysts with high performance and excellent stability. This review summarizes the new findings and in-depth understanding of dynamic structural evolution for Bi-based catalysts, which are revealed by advanced in/ex situ characterization techniques. Furthermore, the dynamic structural evolution of state-of-the-art Bi-based catalysts is summarized based on the classification of derived active phase structures (e.g., metallic Bi, Bi-based alloy, and high-valence Bi sites) after reconstruction. Afterward, the surface Bi defect sites and Bi-based interface structure are strongly confirmed as the intrinsic active sites for eCO₂RR; moreover, the structure-activity relationship of Bi-based catalysts is deeply discussed based on defect engineering and interface engineering modulation. Finally, the perspectives on the future challenges and opportunities in this emerging field are presented, which facilitate to design next-gap advanced electrocatalyst with high performance for eCO₂RR.