Facile in situ synthesis of 2D porous g-C₃N₄ and g-C₃N₄/P25(N) heterojunction with enhanced quantum effect for efficient photocatalytic application

The major challenge of employing photocatalysis for environment protection is to develop high efficient, low cost, and stable semiconductor photocatalysts. In the present study, an in situ annealing strategy is employed for large scale synthesis of two-dimensional (2D) porous graphitic carbon nitride (g-C₃N₄) and efficient g-C₃N₄/P25(N) (N doped P25) heterojunction with enhanced quantum effect. The P25 not only serves as the template for g-C₃N₄ polymerization, but is also modified by the N species to enhance the visible light absorption. Compared to the normal bulk g-C₃N₄, the 2D porous g-C₃N₄ with enhanced quantum effect is found to be more efficient in improving the specific surface area and the electron-hole pair's separation, even its light absorption edge is blue-shifted. Photocatalytic degradation of Rhodamine B (RhB) and phenol indicates the 2D g-C₃N₄ and g-C₃N₄/P25(N) are very efficient and stable under the xenon lamp irradiation. It is also found that the original mass ratio of urea, which is the precursor for g-C₃N₄ synthesis and P25 modification, to P25 also plays a significant effect on the photocatalytic activity. The optimized photocatalyst (mass ratio of P25 to urea is 1:8) can decompose total RhB aqueous solution (10 mg/L, 100 ml) in 25 min. Based on systematic characterizations and discussions, a possible photocatalytic mechanism for the excellent photocatalytic performance is proposed.