Graphitic carbon nitride synthesized at different temperatures for enhanced visible-light photodegradation of 2-naphthol

Abstract Graphitic carbon nitride (g-C 3 N 4 ) was synthesized by one-step calcination at different temperatures for enhanced photodegradation of 2-naphthol under visible light (λ ≥ 420 nm). The g-C 3 N 4 photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet–visible diffuse reflectance spectra (UV–vis DRS). The morphology, band structure and optical property of g-C 3 N 4 could be controlled by the calcination temperature. The formation of genuine g-C 3 N 4 actually began when the temperature was higher than 500 °C. Moreover, compared to the primary stage (450 °C) and the intermediate stage (500 °C and 550 °C), the g-C 3 N 4 synthesized at the advanced stage (600 °C and 650 °C) had not only the strongest absorption of visible light but also the narrowest band gap, enabling controllable adjustment of the band structure of catalysts. Furthermore, the photodegradation efficiency of 2-naphthol was improved as the calcination temperature of g-C 3 N 4 rising up. Meanwhile, g-C 3 N 4 synthesized at 600 °C performed the best with a rate constant of 1.949 h −1 for the first-order kinetic model, which was 2.67 times that of the catalyst synthesized at 450 °C. Finally, the possible photodegradation pathway of 2-naphthol by g-C 3 N 4 was proposed.