Effect of porous modification on the synthesis and photocatalytic activity of graphitic carbon nitride/carbon quantum dot nanocomposite
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Metal-free graphitic carbon nitride (g-C3N4) and carbon quantum dots (CQDs) have a promising attention as to their superior photocatalytic activities and physicochemical properties. In the article, g-C3N4 and CQDs were connected effectively through porous modification of g-C3N4 by directly heating melamine hydrochlorid, which benefits to the enhancement of the composites’ photocatalytic activity. The structures and morphologies of the photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption–desorption, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectrum and photoluminescence spectroscopy. Meanwhile, the porous g-C3N4 and CQDs composite (pg-C3N4/CQDs) exhibited the improved photocatalytic activity for the degradation of RhB under visible light irradiation, which may be contributed three reasons: (1) pg-C3N4 has much higher surface area (~ 20 times) and more stronger photocatalytic oxidation capacity than that of g-C3N4; (2) as the electron-sinks, CQDs can improve the photogenerated electron–hole pair’s separation; (3) CQDs can upconvert the light with wavelengths longer than 650 nm into the shorter wavelengths to increase light harvesting, while pg-C3N4 utilizes the light to degrade pollutants. In addition, the possible photocatalytic degraded mechanism was investigated in detail. This work will be useful for designing other CQDs-based photocatalysts and providing a promising approach to environmental purification.
This work was supported by Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi (Grant No. 2015128), and Qualified Personnel Foundation of Taiyuan University of Technology (QPFT) (Grant No. tyutrc-201326c) and the Shanxi Provincial Key Research and Development Plan (general) Social Development Project (Grant No. 201703D321009-5).
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