*3.4. Synthesis of g-C3N4/TiO2 Composites*

g-C3N4/TiO2 composites were prepared by a hydrothermal method. Firstly, TiOSO4 suspensions were obtained by sonication for 35 min in D.I. water. After dispersing, CNS was added into the solution and was sonicated continuously for 30 min. The solution was transferred to a Teflon-lined autoclave which was then further heated at 180 ◦C for 4 h. The obtained solution was centrifuged, washed with D.I. water, and dried at 65 ◦C for 24 h. According to the above method, different weight ratios of g-C3N4 to TiO2 at 0.5%, 1%, 4%, 10%, and 15% were synthesized and labeled as 0.5CNS/TiO2, 1CNS/TiO2, 4CNS/TiO2, 10CNS/TiO2, and 15CNS/TiO2, respectively. TiO2 was also prepared by the same procedure without adding g-C3N4.
