Preparation and photocatalytic properties of ZnO nanorods/g-C3N4 composite

ZnO nanorods/g-C3N4 photocatalytic composite was prepared, and its structural and optical properties have been studied. Bulk graphite phase carbon nitride (g-C3N4) was first prepared by a one-step thermal polymerization method, and ZnO nanorods were grown from the ZnO seed particles on the surface of g-C3N4 by a hydrothermal method. The effects of hydrothermal reaction time on the morphology and photocatalytic properties of ZnO nanorods/g-C3N4 composite were investigated. The hydrothermal reaction included two stages. The initial stage was dominated by the rapid deposition of Zn2+ precursor in hydrothermal solution on ZnO seed particles to form ZnO seed layer, and the second stage was the hydrothermal growth of ZnO nanorods from the ZnO seed layer. In the second stage, two processes occurred simultaneously, namely, the dissolution of seed layer and the growth of ZnO nanorods. Hence, the composite prepared with different hydrothermal time shows different photocatalytic degradation mechanism to methyl orange (MO) solution. The photocatalytic performance of the composite sample with the grown time of 2 h is mainly attributed to separation efficiency of photogenerated carriers. For the composite sample with the grown time of 3 h, due to the partial dissolution of seed layer, its photocatalytic performance is mainly attributed to the surface reaction of ZnO nanorods. For the composite samples with the hydrothermal grown time of 4 and 5 h, the dense ZnO nanorods on the surface of g-C3N4 improve the separation efficiency of the photogenerated carriers, and their photocatalytic performance is attributed to both carrier lifetime and surface reaction. As a result of synergy, the sample with the hydrothermal grown time of 3 h shows the best photocatalytic performance in all composite sample.