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Synthesis of a well-dispersed CaFe₂O₄/g-C₃N₄/CNT composite towards the degradation of toxic water pollutants under visible light

Liu, Fei, Dong, Shaocan, Zhang, Zhaoxiang, Li, Xiaqing, Dai, Xiaodong, Xin, Yanping, Wang, Xuewu, Liu, Kun, Yuan, Zhenhe, Zheng, Zheng
RSC advances 2019 v.9 no.44 pp. 25750-25761
X-ray photoelectron spectroscopy, carbon nanotubes, carbon nitride, chromium, graphene, hydrogen production, irradiation, oxidation, photocatalysis, photocatalysts, photoluminescence, photosensitizing agents, pollutants, reflectance spectroscopy, scanning electron microscopy, semiconductors, tetracycline, toxicity, transmission electron microscopy
Herein, we fabricated a ternary photocatalyst composed of CaFe₂O₄, multiwalled carbon nanotubes (CNTs) and graphitic carbon nitride (g-C₃N₄) via a simple hydrothermal route. CaFe₂O₄ acted as a photosensitizer medium and the CNT acted as a co-catalyst, which remarkably enhanced the photocatalytic performances of g-C₃N₄ towards the degradation of hexavalent chromium (Cr(vi)) and the antibiotic tetracycline (TC) under visible light irradiation. To investigate the morphological and topological features of the photocatalyst, field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) analyses were performed. The surface properties and oxidation state of the CaFe₂O₄/g-C₃N₄/CNT composite were determined by X-ray photoelectron spectroscopy (XPS). The recombination rate of the charge carriers and the band gap values of the as-synthesized catalysts were analyzed by photoluminescence spectroscopy (PL) and diffused reflectance spectroscopy (UV/Vis DRS) studies, respectively. Besides the degradation reactions, the high hydrogen production rate of 1050 μmol h⁻¹ under visible light using the CaFe₂O₄/g-C₃N₄/CNT composite loaded with 5 wt% CNT was observed. The superior photocatalytic performances of the CaFe₂O₄/g-C₃N₄/CNT composite can be ascribed to the effective heterojunction formed between g-C₃N₄ and the CaFe₂O₄ matrix, in which the CNT act as a conducting bridge in the system, promoting the production of photoinduced charge carriers in the semiconductor system. Finally, the plausible photocatalytic mechanism towards the degradation of pollutants and hydrogen production was discussed carefully.