BACKGROUND Environmental pollution and energy crisis are nowadays considered among the most important problems facing humanity. Several strategies have been proposed to solve them, being photocatalysis a very promising one because of its ease of application and low cost. In the search for active photocatalysts, those based on graphite-like carbon nitride (g-C3N4) are becoming good alternatives for various reactions. In this work, the properties of g-C3N4/MoS2/MnOOH composite material and its photocatalytic behavior for the production of hydrogen (H-2) under UV radiation were investigated. RESULTS The composite material was synthesized by applying a combination of thermal condensation and hydrothermal methods. According to the results of X-ray diffraction (XRD), ultraviolet diffuse reflectance spectroscopy (UV-DRS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), good dispersion of the phases and the formation of a heterojunction were observed. The band gap value of the composite material, calculated by the Kubelka-Munk equation using the values obtained from UV-DRS analysis, was lower than those of the individual components, while it also had a much longer electron-hole recombination time, according to photoluminescence analysis. As a consequence of a synergistic effect, the activity of the proposed composite photocatalyst was superior in the reaction of water splitting, with a kinetic constant of 466 mu mol h(-1) and a production rate of 1750 mu mol H-2 gcat-1 h(-1) (50 and 21% higher than those obtained with MoS2 and g-C3N4, respectively). CONCLUSION Because of its high activity and stability, g-C3N4/MoS2/MnOOH composite photocatalyst is an excellent alternative for H-2 production by the water splitting reaction. (c) 2019 Society of Chemical Industry