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Indexed by:期刊论文

Date of Publication:2018-01-01

Journal:CHEMOSPHERE

Included Journals:SCIE、EI、PubMed

Volume:190

Page Number:135-143

ISSN No.:0045-6535

Key Words:Metal-free; Fluorine-doped carbon nanotubes; Catalytic ozonation; Superoxide radicals; Singlet oxygen

Abstract:Metal-free carbon materials have been presented to be potential alternatives to metal-based catalysts for heterogeneous catalytic ozonation, yet the catalytic performance still needs to be enhanced. Doping carbon with non-metallic heteroatoms (e.g., N, B, and F) could alter the electronic structure and electrochemical properties of original carbon materials, has been considered to be an effective method for improving the catalytic activity of carbon materials. Herein, fluorine-doped carbon nanotubes (F-CNTs) were synthesized via a facile method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The as-synthesized F-CNTs exhibited notably enhanced catalytic activity towards catalytic ozonation for the degradation of organic pollutants. The oxalic acid removal efficiency of optimized F-CNTs was approximately two times as much as that of pristine CNTs, and even exceeded those of four conventional metal-based catalysts (ZnO, Al2O3, Fe2O3, and MnO2). The XPS and Raman studies confirmed that the covalent C-F bonds were formed at the sp(3) C sites instead of sp(2) C sites on CNTs, not only resulting in high positive charge density of C atoms adjacent to F atoms, but remaining the delocalized pi-system with intact carbon structure of F-CNTs, which then favored the conversion of ozone molecules (O-3) into reactive oxygen species (ROS) and contributed to the high oxalic acid removal efficiency. Furthermore, electron spin resonance (ESR) studies revealed that superoxide radicals (O-2 center dot(-)) and singlet oxygen (O-1(2)) might be the dominant ROS that responsible for the degradation of oxalic acid in these catalytic systems. (C) 2017 Elsevier Ltd. All rights reserved.