In this study, an S-doped g-C3N4 nanosheet was prepared as a photocatalyst for effective oxygen evolution reaction. Sulfur plays a crucial role in S-doped g-C3N4 not only in increasing the charge density but also in reducing the energy band gap of S-doped g-C3N4 via substitution of nitrogen sites. S-doped g-C3N4 can serve as an oxygen-evolved photocatalyst, when combined with Ru/SrTiO3:Rh in the presence of [Co(bpy)(3)](3+/2+) as an electron mediator, enables photocatalytic overall water splitting under visible light irradiation with hydrogen and oxygen production rates of 24.6 and 14.5 mu mol-h(-1), respectively. Moreover, the photocatalytic overall water splitting to produce H-2 and O-2 using this Z-scheme system could use for five runs to at least 94.5 h under visible light irradiation. On the other hand, S-doped g-C3N4 can reduce biofouling by bacteria such as Escherichia toll by more than 70%, by simply incubating the Sdoped g-C3N4 sample with bacterial solution under light irradiation. Our results suggest that S-doped g-C3N4 is a potentially effective, green, and promising material for a variety of photocatalytic applications. (C) 2020 Elsevier Inc. All rights reserved.