One step and fast preparation of VOx/g-C3N4 photocatalyst via microwave heating for effective degradation of RhB under visible light

Abstract This work reports a microwave heating method for synthesis of a VOx/g-C3N4 complex for applications in photocatalytic degradation of rhodamine B (RhB) under visible light illumination. The facile strategy allows the fabrication of the VOx/g-C3N4 composite in 40 min with NH4VO3 and melamine as precursors. A thorough investigation was performed to investigate the structure, morphology, photoabsorption performance and charge separation capability of the VOx/g-C3N4 composite. XRD, FT-IR, XPS and TEM experiments proved that VOx nanoparticles which have the mixed valence state of V5+ and V4+ were dispersed in the g-C3N4. DRS experiment demonstrated that these introduced VOx nanoparticles improved the light absorption property for visible light. N2-adsorption analysis showed that the surface area of VOx/g-C3N4 sample was enhanced with increasing VOx content. Although the improved photoabsorpion performance and surface area are beneficial to the photocatalytic RhB degradation, the mostly important reason of the enhanced photoactivity was ascribed to the formed heterojunction structure of g-C3N4 and VOx, which triggers electrons migration via a type-II mechanism and elevates the charge separation. This improved charge separation was confirmed by the PL, EIS, and PC experiments, while the type-II mechanism was verified by reactive species trapping experiment and photocatalytic H2 evolution test. Due to the improved efficiency in separating charge carriers, the VOx/g-C3N4 worked very well in RhB degradation via photocatalysis. The best VOx/g-C3N4 sample displayed a RhB degradation velocity of 0.079 min−1 under visible light, which is 3.6 folds faster than that of neat g-C3N4.