Biomass-derived Fe3C@CNT catalyst for catalytic ozonation through confinement-enhanced electron transfer and ozone activation

One-step pyrolysis enabled Fe/N co-doping to form CNT-confined Fe 3 C structures; • Fe 3 C-derived Lewis acidic sites served as the primary centers for activating O 3 ; • Fe 2+ /Fe 3+ redox cycling promoted ozone activation and ROS generation; • Confinement enhanced O 3 enrichment, •OH yields, and ion tolerance during FeN-BC/O 3 ; • •OH was confirmed as the key oxidizing species for IBP removal; Active metal leaching, inefficient ozone activation, and limited interfacial mass/electron transfer are key factors restricting the performance of conventional catalytic ozonation catalysts. To address these issues, a biomass-derived Fe/N co-doped carbon nanotubes with a nano-confinement structure (FeN-BC) was synthesized via one-pot pyrolysis of rapeseed straw, FeCl 3 •6H 2 O, and melamine at 700 °C under N 2 followed by acid washing and purification. SEM, TEM, and XRD results revealed that Fe and N co-doping promoted in-situ growth of carbon nanotubes with stable encapsulation of Fe 3 C nanoparticles by graphitic layers. In the catalytic ozonation of ibuprofen (IBP), FeN-BC achieved 91.5% removal within 60 min, outperforming sole ozonation and control catalysts (BC, Fe-BC, N-BC). On account of the synergistic function of Fe and N, the Fe 3 C active center exhibited excellent stability, with iron leaching remaining below 0.1 mg L −1 , whereas Fe-BC released 0.51 mg L −1 iron. In addition, FeN-BC retained good catalytic activity after five consecutive cycles. Furthermore, FeN-BC maintained excellent catalytic stability across pH 3–9 and with various inorganic anions (Cl − , SO 4 2− , NO 3 − , H 2 PO 4 − ). •OH was identified as the dominant reactive species, contributing 86.86% to IBP degradation. Electrochemical and DFT results demonstrated that the nano-confinement effect enhanced interfacial electron transfer, with Fe 3 C Lewis sites serving as the primary active center. IBP degradation followed three pathways, yielding 18 intermediates and accompanied by progressive detoxification. This work advances the understanding of nano-confinement enhanced ozone activation and promotes the development of sustainable biomass-derived catalysts for water purification. Download: Download high-res image (147KB) Download: Download full-size image