The CNT modified white C3N4 composite photocatalyst with enhanced visible-light response photoactivity

Abstract

A novel, multi-walled carbon nanotubes (CNT) modified white C₃N₄ composite (CNT/white C₃N₄) with enhanced visible-light-response photoactivity was prepared. The white C₃N₄ and CNT combined together and formed the CNT/white C₃N₄ composite due to electrostatically-driven self-assembly with the hydrothermal method. The as-prepared white C₃N₄ and CNT/white C₃N₄ composite photocatalyst were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-vis absorption spectra, X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The photoelectrochemical i–t curves were tested using several on–off cycles of light irradiation. The photoactivity of the catalysts was evaluated by degrading methylene blue (MB) dye solution. The results showed that the photoactivity for the degradation of MB solution was in the following order: CNT/white C₃N₄ composite > C₃N₄ > the white C₃N₄. The photoactivity of the CNT/white C₃N₄ composite was 66.5% and 34.5% higher than that of the white C₃N₄ sample and that of the C₃N₄ at 1.5 h, respectively. The degradation rate of the CNT/white C₃N₄ photocatalyst was almost 8.1 times as high as that of the white C₃N₄. The results indicated that CNT played an important role, which led to the efficient separation of the photo-generated charge carriers. The reason why the photoactivity of the CNT/white C₃N₄ was much higher than that of C₃N₄ and the white C₃N₄ was discussed. A possible mechanism of CNT on the enhancement of composites' visible light performance was also proposed.