Enhancement of hydrogen peroxide production by electrochemical reduction of oxygen on carbon nanotubes modified with fluorine

It is vital to synthesis hydrogen peroxide via electrochemical reduction of oxygen since it is a green process to produce oxidant with wide applications including water/wastewater treatment. In this work, fluorine (F) was employed to modify carbon nanotube (CNT), and the obtained F doped CNT (F-CNT) catalyst was used to fabricate gas diffusion electrode (GDE). It was found that F doping could improve oxygen reduction activity and H₂O₂ selectivity, and then enhanced the H₂O₂ production. After modification, F-CNT prepared with 0.6 M HF (CNT-F-0.6) had much higher H₂O₂ production (47.6 mg L⁻¹) and current efficiency (89.5%) than that of CNT (29.6 mg L⁻¹, 70.1%) at bias voltage of −1.3 V (vs SCE) and pH 7. Moreover, the high catalytic activity of CNT-F-0.6 could maintain in 5 consecutive reaction cycles. The material characterization and electrochemical test indicated that F doping had no significant effects on the surface area of CNT, but improved the defect degree of CNT. The enhanced H₂O₂ production performance could be ascribed to the formation of CF₂ and CF₃ on the surface of F-doped CNT, which rendered the potential for practical application of novel carbon catalyst for GDE.