Significant Improvement of Photocatalytic Activity of TiO2/g–C3N4 Composite Synthesized by the Aiding of Hydrothermal Method

Abstract

g–C3N4 nanosheets were first synthesized by calcining the mixture of hydrochloric acid-pretreated melamine and ammonium chloride. Then, by the aiding of solvothermal method and hydrofluoric acid as morphology modifier, 001-TiO2/g–C3N4 (TCN-X, [Formula: see text], 3, 2, 1) nanocomposites were synthesized using g–C3N4 nanosheets and tetrabutyl titanate, with the mass ratio of g–C3N4 to TiO2 was 5:1, 3:1, 2:1 and 1:1, respectively. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption method, ultraviolet–visible diffuse reflectance spectrum, photoluminescence spectrum, etc. Their photocatalytic properties were evaluated under visible light irradiation with rhodamine B (RhB) as the target pollutant. The results reveal that the TCN-3 composites had a large specific surface area of 67.38[Formula: see text]m2/g and consisted of g–C3N4 nanosheets and anatase TiO2 crystals about 10–20[Formula: see text]nm in size. The (001) crystal planes of TiO2 can be easily observed in TCN-X composites. All TiO2/g–C3N4 composites exhibited excellent photocatalytic activity compared with the pure g–C3N4 did. The photocatalytic property of TCN-X samples varied with the mass ratio of g–C3N4to TiO2, and TCN-3 presented the optimum photocatalytic performance. In total, 50[Formula: see text]mg of TCN-3 completely degraded 50[Formula: see text]mL and 100[Formula: see text]mL of RhB solution (10[Formula: see text]mg/L) in 15[Formula: see text]min and 40[Formula: see text]min, respectively. The reaction rate constant of TCN-3 was 6.7 times as large as that of pure g–C3N4. TCN-3 also presented outstanding activity for the photocatalytic degradation of the colorless tetracycline solution. The significant improvement in photocatalytic activity of TCN-3 was attributed to the evenly distribution of TiO2 on g–C3N4, the enhanced specific surface area and the construction of 001-TiO2/g–C3N4 heterojunction between the g–C3N4 nanosheets and the (001) crystal planes of anatase TiO2, which greatly reduced the recombination rate of the photo-generated electron and hole.