Facile synthesis of porous isotype heterojunction g-C3N4 for enhanced photocatalytic degradation of RhB under visible light

Abstract

To improve the comprehensive photocatalytic performance of g-C3N4, a facile co-polycondensation method was applied to synthesize porous isotype heterojunction g-C3N4 using urea and melamine as precursors. The microstructure of as-prepared samples was revealed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption desorption test, Fourier-transform infrared spectra, X-ray photoelectron spectroscopy, and thermogravimetry. The product yield and thermal stability of the isotype g-C3N4 was improved. Photocatalytic performance of all samples was evaluated by photodegradation of Rhodamine B under visible light. The results show that U3M1 sample (with urea-to-melamine ratio of 3:1) exhibits the highest photocatalytic efficiency, and the corresponding apparent rate constant is around 1.4 and 6.7 folds than that of U1M0 (with pure urea) and U0M1 (with pure melamine), respectively. The enhanced photocatalytic activity can be attributed to the hierarchically porous isotype heterojunction structure, which not only improves the charge separation efficiency, but also reduces the electron-hole recombination. In addition, the porous isotype heterojunction g-C3N4 displays excellent reusability after suffering 4 cyclic tests. This work provides a feasible method for preparing g-C3N4 with high photocatalytic efficiency, and promotes the application of g-C3N4 in the purification of dye wastewater.