Electrochemically controlled in situ conversion of CO₂ to defective carbon nanotubes for enhanced H₂O₂ production

Defects on carbon nanotubes (CNTs) can be used as active sites to promote the occurrence of catalytic reactions and improve the ability of catalysts. Although some progress has been made in the synthesis of defects on carbon nanotubes (CNTs), most of the defects are caused by acid etching or high-temperature pyrolysis of organics, which is detrimental to the environment, and the defects are uncontrollable. Herein, we report the eco-friendly and controllable synthesis of defective CNTs by reduction of CO₂ under cathodic polarization in Li₂CO₃-based molten salts. The defective degree of CNTs can be tuned by changing the applied electrolysis current. The results show that low current is beneficial for the synthesis of CNTs with more defect sites. The most defect-rich carbon nanotubes synthesized under 300 mA cm^-2 electrolysis (CNTs-B₂O₃-300) in a molten Li₂CO₃/B₂O₃ composite melt performed the best in the 2e^- oxygen reduction reaction (ORR) compared with CNTs-B₂O₃-400 and CNTs-B₂O₃-500 obtained under higher current density electrolysis. This work provides an alternative strategy for the design and synthesis of defect-rich carbon materials for catalysis and energy applications.