Significant enhancement of photocatalytic activity of g-C3N4/vermiculite composite by the introduction of nitrogen defects

Nitrogen-defect g-C3N4/vermiculite composites (gCVx, x = 0.1, 1, 3, 4) with high efficient photocatalytic per-formance were constructed by a wet chemical method cooperating with the calcination process, as well as using the pre-expanded vermiculite and the melamine pre-treated by hydrochloric acid solutions of 0.1, 1, 3, 4 mol/L, respectively. Micron-sized g-C3N4 sheets with nitrogen defects were synthesized and uniformly distributed in the gCVx composites. Photocatalytic performance was evaluated by degrading Rhodamine B (RhB) aqueous solution. The results indicated that photocatalytic activities of gCVx increased firstly and then dropped down gradually with the increase of HCl concentration. gCV3 achieved the maximum degradation rate of 97.90 % for RhB after photocatalysis for 20 min, whose degradation rate constant was 14.9 times than that of bulk g-C3N4. gCV3 also exhibited the highest photocatalytic activity toward degrading the tetracycline and phenol solutions. The excellent photocatalytic performance was ascribed to the enhanced amounts of active sites, increased specific surface area, improved visible light absorption ability, accelerated charge transfer and separation efficiency of photogenerated-carriers, which resulted from the synergistic effect between vermiculite and nitrogen defects in g-C3N4, as well as the mutual electrostatic repulsion between the negative-charged vermiculite and the photo-induced electron from the nitrogen-defect g-C3N4.