One-pot synthesis of g-C3N4/diatomite composite with nitrogen vacancies for enhanced photocatalytic activity

The g-C3N4/diatomite (g-C3N4/DT) composites were prepared by a one-step thermal polycondensation method using melamine and diatomite as sources. The photocatalytic properties of the g-C3N4/DT composites with different mass ratios of melamine to diatomite were investigated by degradation of RhB under visible light and simulated solar irradiation. When the amount of carbon nitride loaded onto diatomite is appropriate, the obtained S600-10-3 exhibits a degradation rate of 98.3 % toward RhB under visible light irradiation for 30 min. The reaction rate constant of S600-10-3 under visible light is 0.124 min−1, which is 2.25 times that of g-C3N4 (0.055 min−1) and 6.89 times that of P25. In addition, S600-10-3 has good photochemical stability and reusability for RhB degradation. Additionally, S600-10-3 also shows a high degradation rate of 97.3 % toward TC. Hole, superoxide radicals and singlet oxygen are responsible for the photodegradation of RhB, while the active species for TC photocatalytic degradation are holes and superoxide radicals. The mineralization rates of RhB and TC over S600-10-3 are around 95.4 and 66.8 % after 30 and 80 min visible-light irradiation, respectively. The outstanding photocatalytic efficiency of g-C3N4/DT composite (S600-10-3) is attributed to the porous lamellar/tubular structure of carbon nitride with nitrogen vacancies, the reduced recombination rate of the photogenerated electrons and holes, and the synergistic effect of diatomite and carbon nitride.