The photocatalytic activity of bulk g-C3N4 is rather low. Many strategies have been adopted to improve the photocatalytic performance of g-C3N4. Here, Na and O co-doped g-C3N4 was prepared by a feasible solvothermal method. The band structure was modulated mainly by introducing O into lattice of g-C3N4, resulting in simultaneously enhanced absorption and red shift. Moreover, the separation and migration of photogenerated carriers under visible light was enhanced by Na doping. In addition, well dispersion of (Na, O)-g-C3N4 in pure water was observed due to its high surface electronegativity. The photocatalytic H-2 production activity of (Na, O)-g-C3N4 was improved tremendously, especially under visible light, and the apparent quantum yield was as high as 22.3% at 420 nm. (C) 2017 Elsevier B.V. All rights reserved.