A novel microwave-assisted impregnation method with water as the dispersion medium to synthesize modified g-C3N4/TiO2 heterojunction photocatalysts

A microwave-assisted impregnation method with water as the dispersion medium was developed to prepare KCNN (K doped g-C3N4 nanosheets)-TiO2 heterojunction composite material (KCNNT). With this novel method, KCNN and TiO2 can be evenly dispersed during synthesis to make large number of effective heterojunctions, thus offering high photocatalytic efficiency. Moreover, the use of water, instead of chemical reagents, as the dispersant makes this method both cost- and environmental-friendly. The photocatalytic degradation efficiency of RhB by KCNNTM synthesized by the microwave-assisted impregnation method was 1.23 times higher than that of KCNNTH synthesized by the thermal radiation assisted impregnation method. In addition, the photocatalytic degradation efficiency of RhB by the KCNNT0.5M (formed with the KCNN and TiO2 at ratio of 1:0.5) was 2.4 times higher than that of the CNT0.5M (formed with pure g-C3N4 and TiO2 at ratio of 1:0.5), indicating the importance of modification of g-C3N4 before the formation of composite materials. KCNN formed Z-type heterojunction with TiO2, which improved the separation efficiency of electron-hole and greatly improved the photocatalytic efficiency. The photocatalytic degradation efficiency of RhB by the KCNNT0.5M was 4.1 times higher than that of pure g-C3N4 under visible light.