Second-scale synthesis of oxygen-doped carbon nanotubes for oxygen reduction to hydrogen peroxide and valorization

Heteroatom-modified carbon materials serve as efficient electrocatalysts for the two-electron oxygen reduction reaction (2e^- ORR) to produce hydrogen peroxide (H₂O₂). However, the protracted material preparation cycle and the unclear microenvironment of the electrode interface pose limitations on further development. This work presents a flame-assisted strategy that rapidly synthesizes oxygen-doped carbon nanotubes (O-CNTs) in ∼40 s and delivers a catalyst with an H₂O₂ yield rate of up to 0.42 mmol cm^-2 h^-1 under alkaline conditions in an H-cell and over 90% Faradaic efficiency across a wide potential range. Microenvironment analysis at the electrode interface reveals that O-CNTs enhance water dissociation capacity and proton transport kinetics, supplying sufficient active hydrogen for efficient H₂O₂ production. Moreover, we discover that as the overpotential increases, the generated carbon defects accumulate and activate water. The oxygen from the water can undergo nucleophilic attack on carbon defects to achieve oxygen exchange. To better align with the practical application prospects, we further assemble an electrochemical flow reactor and achieve a cumulative H₂O₂ concentration of ∼1.5 wt%. Finally, we harness the oxidizing properties of H₂O₂ to explore its potential in synthesizing inorganic peroxides (Na₂CO₃∙1.5H₂O₂) and in the selective oxidation of organic (5-hydroxymethylfurfural).