Photocatalytic technology for hydrogen evolution from water splitting and pollutant degradation is one of the most sustainable methods. Here, the graphene/g-C3N4-Co composite materials have been prepared by one-pot calcination method. The results show that g-C3N4 grow on the surface of graphene and form a sandwich structure, meanwhile, the introduction of Co increases the active sites, which promotes the photocatalytic performance. The influences of graphene and Co content on photocatalytic activity were also studied by UV-visible spectrophotometry (DRS), photoluminescence spectroscopy (PL), photocurrent, degradation MB, and hydrogen production. The apparent reaction rate constant k of graphene/g-C3N4-Co (3%) is 0.946 h(-1), which is 4.90 and 2.18 times faster than g-C3N4 and graphene/g-C3N4, respectively. And the hydrogen production rate of graphene/g-C3N4-Co (3%) (892.3 mu mol h(-1) g(-1) is 3.53 and 1.61 times higher than g-C3N4 and graphene/g-C3N4, respectively. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.