Preparation of g-C3N4/TiO2 Nanocomposites and Investigation of Their Photocatalytic Activity

Three kinds of g-C3N4/TiO2 nanocomposites with different composition were prepared by calcination of titanic acid nanotubes (TAN) and melamine at 550 degrees C. The as-synthesized g-C3N4/TiO2 nanocomposites were characterized by means of X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, fast Fourier transform infrared spectroscopy, and ultraviolet-visible light-diffuse reflectance spectra (UV-vis DRS). Furthermore, the photocatalytic activity of g-C3N4/TiO2 nanocomposites was evaluated in the degradation of methyl orange under visible light irradiation. Our findings indicate that, after the mixed precursors of TAN and melamine are calcinated at elevated temperature, TAN is transformed to a novel anatase TiO2 with visible light response while melamine is transformed to g-C3N4. Such novel TiO2 contains a large amount of single electron trapped oxygen vacancies which can form a sub-band in the forbidden band of TiO2, thereby inducing visible light response. As a result, the novel TiO2 and g-C3N4 can be both excited by the visible light. The as-synthesized g-C3N4/TiO2 nanocomposites exhibit good photocatalytic activity for the degradation of methyl orange. Besides, the introduction of C3N4 causes a decrease in the size of TiO2 nanoparticles as well as remarkable red-shift of UV-vis DRS spectra of TiO2. Moreover, the g-C3N4/TiO2-2 nanocomposite obtained using initial molar ratio of melamine to TAN of 1:2 exhibits the best photocatalytic activity among the three kinds of as-prepared nanocomposite, showing good long-term stability.