Increased charge transfer and light absorption as well as large specific surface area are effective ways to improve the catalytic efficiency of photocatalysts. In this paper, barbituric acid, urea and thiourea were separately freeze-dried to form a homogeneous precursor with melamine, followed by thermal polymerization at 750 degrees C, g-C3N4 was doped successfully with C, N and S. Among them, C-doped g-C3N4 revealed well photocatalytic hydrogen production which reached to 2.45 mmol g(-1) h(-1). N-doped g-C3N4 exhibited enhanced photocatalytic degradation properties for organic dye (RhB) which is completely degraded within 8 min while the performance S-doped sample is not satisfied. The introduction of C resulted in planarized sample which has a larger specific surface area and provides more active sites. N doping makes the valence band position moving in the direction of high energy. Thus, holes have stronger oxidizing ability. Accordingly, the effect of C and N ratios in g-C3N4 photocatalysis was fully discussed for more comprehensive understanding of g-C3N4. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.