In this work, the nitrogen-doped carbon nanotubes with encapsulated Fe 3 C nanoparticles (Fe 3 C@NCNTs) were prepared through a simple process by pyrolyzing the precursor of ferric trichloride hexahydrate and melamine composite. It was studied systematically that multiple Fe 3 C@NCNTs synthesized under 600–1000 °C activated persulfate (PS) for the degradation of sulfamethoxazole (SMX), a widely used antibiotic of sulfonamides. Raman spectrum , X-Ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS) were used to characterize the transformation of catalyst with the increase of annulling temperature. The Fe 3 C@NCNTs synthesized under 800, 900 and 1000 °C showed similar degradation ability to SMX with degradation rates of 0.650–0.893 min −1 . During catalytic process, the specific structure of Fe 3 C encapsulated NCNTs could both benefit the electron transfer and prevent the Fe 3 C dissolving in the solution. The results of quenching experiments coupling with electron paramagnetic resonance (EPR) spectra suggested the OH, SO 4 − and 1 O 2 contributed to the degradation of SMX and the singlet oxygen took effect for longer time. The degradation intermediates were mainly derived from the reactions of hydroxylation, oxidation , aniline ring opening, deamination, desulfonation, as well as bond cleavage. In terms of the density functional theory (DFT) calculations, the graphitic N exhibited the highest ΔE ads (−0.437 eV) for the PS molecule, and it was followed by the pyrrolic N (−0.304 eV), pristine graphene (−0.146 eV) and pyridine N (−0.072 eV), which means that the graphitic N is more favorable for the binding affinity with PS, forming the reactive complexes on the surface of the NCNTs catalysts to promote the nonradical oxidation.
Graphical All-round activity : Hybrids of Fe/Fe 3 C embedded in N-doped carbon nanotubes (Fe/Fe 3 C@NCNTs) are prepared by pyrolyzing mixtures of Fe 3 O 4 nanoparticles and dicyandiamide. Fe/Fe 3 C@NCNTs show a highly multifunctional catalytic activity for the oxygen evolution, oxygen reduction, and CO 2 reduction reactions. Hybrids of Fe/Fe 3 C embedded in N-doped carbon nanotubes (Fe/Fe 3 C@NCNTs) are prepared by pyrolyzing mixtures of Fe 3 O 4 nanoparticles and dicyandiamide. The systematic electrochemical study of Fe/Fe 3 C@NCNTs shows a decent catalytic activity toward the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). The sample of Fe/Fe 3 C@NCNTs at 750 °C exhibits a remarkably high activity with an onset potential of 1.47 V for the OER, and an onset potential of 0.96 V and half-wave potential 0.88 V for the ORR, which inspired us to set up a rechargeable Zn-air battery with such Fe/Fe 3 C@NCNT nanohybrids as the cathode materials, showing a maximum power density of 198 mW cm −2 and long-term stability after 500 cycles. We also demonstrate that Fe/Fe 3 C@NCNTs present favorable electrocatalytic activity towards the CO 2 reduction reaction (CO 2 RR) with a low onset potential and good selectivity. The major products are a mixture of H 2 and CO gases that can be used for methanol production in the Fischer−Tropsch process.
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