Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024, China.
Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024, China.
Chemosphere. 2018 Jan;190:135-143. doi: 10.1016/j.chemosphere.2017.09.119. Epub 2017 Sep 27.
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, AlO, FeO, and MnO). The XPS and Raman studies confirmed that the covalent CF bonds were formed at the sp C sites instead of sp C sites on CNTs, not only resulting in high positive charge density of C atoms adjacent to F atoms, but remaining the delocalized π-system with intact carbon structure of F-CNTs, which then favored the conversion of ozone molecules (O) 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) and singlet oxygen (O) might be the dominant ROS that responsible for the degradation of oxalic acid in these catalytic systems.
金属碳材料已被证明是多相催化臭氧化中金属基催化剂的潜在替代品，但催化性能仍需提高。在碳中掺杂非金属杂原子（如 N、B 和 F）可以改变原始碳材料的电子结构和电化学性质，被认为是提高碳材料催化活性的有效方法。本文通过一种简便的方法合成了氟掺杂碳纳米管（F-CNTs），并通过 X 射线衍射（XRD）、X 射线光电子能谱（XPS）和拉曼光谱对其进行了表征。所合成的 F-CNTs 对催化臭氧化降解有机污染物表现出显著增强的催化活性。优化后的 F-CNTs 的草酸去除效率约为原始 CNTs 的两倍，甚至超过了四种传统金属基催化剂（ZnO、AlO、FeO 和 MnO）。XPS 和拉曼研究证实，CF 键是在 sp C 位而不是 CNTs 的 sp C 位形成的，这不仅导致相邻 F 原子的 C 原子的正电荷密度很高，而且还保持了 F-CNTs 的完整碳结构的离域π体系，从而有利于臭氧分子（O）转化为活性氧物种（ROS），并有助于提高草酸的去除效率。此外，电子顺磁共振（ESR）研究表明，超氧自由基（O）和单线态氧（O）可能是这些催化体系中负责降解草酸的主要 ROS。
