Tailoring Oxygen Vacancies of BiOBr Nanosheets via Rapid Electron Beam Irradiation for Efficient Electrocatalytic CO ₂ Reduction to Formate

High-valence bismuth species (e.g., BiOBr) have attracted significant attention as electrocatalysts for CO2 reduction to formate due to their superior structural stability and product selectivity. However, exploring a synthesis strategy that is rapid, energy-efficient, and operationally simple remains a key challenge. Herein, we reported, for the first time, a rapid and scalable electron beam irradiation strategy to synthesize BiOBr nanosheets within only 10 min. By precisely tuning the irradiation dose, the structural features and catalytic performance of BiOBr nanosheets achieving control over oxygen vacancies (Ov) concentrations could be effectively modulated. At an optimal dose of 300 kGy, the catalyst achieves a Faradaic efficiency (FE) of 95.0% ± 0.48% for formate production in the flow cell. To further reduce the cost associated with product separation, a solid-electrolyte cell was adopted to achieve continuous production of 0.08 M pure HCOOH with a FE of 88.4%. Systematic in situ electrochemical analysis further indicated that electron beam-induced defects, particularly Ov, play a critical role in CO2 activation and *OCHO intermediate formation, correlating strongly with enhanced catalytic performance. This study not only highlights the potential of electron beam irradiation for the synthesis and engineering high-performance Bi-based catalysts but also offers a promising strategy for scalable nanomaterial synthesis and efficient CO2-to-formate conversion.