The heterostructures of graphitic carbon nitride (g-C3N4) and CdS were synthesized by controlling the crystalline degree of g-C3N4 and the phase composition of CdS. A thermal polycondensation process of N precursors was adjusted to get amorphous and crystalline g-C3N4. A multistep adsorption method was used to deposit CdS nanoparticles on g-C3N4. An annealed process was used to adjust the phase composition of CdS from cubic to hexagonal. The morphology of CdS was changed to rod. Amorphous g-C3N4/CdS heterostructures revealed enhanced photocatalytic activity because the amorphous g-C3N4 has a lower crystallinity, it is easier to form a heterojunction with the CdS. Further, an annealing process resulted in the phase transfer and morphology change of CdS. The high stability and rod morphology of CdS make the heterostructures with high H-2 generation rate to 5440 mu mol h-1 g-1 which is similar to 5 times high compared with g-C3N4. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.