In this work, ZnO/rGO nanocomposites (NCs) were synthesized through a low temperature sol-gel method. Zinc oxide decorated on graphene sheets could provide surface enhancement and hinder the rapid recombination rate of electron hole pairs that occur during a photocatalysis process. It has been observed that the loading of ZnO decorated on graphene sheets is important in controlling the morphologies and surface enhancement of ZnO/rGO NCs. Field Emission Scanning Electron Microscope (FESEM) micrographs reveal that spherical shape and hexagonal-based nanopyramid of ZnO can be formed at low and high loading of ZnO, respectively. NCs showed excellent performance for degradation of perfluorooctanoic acid (PFOA) and methyl orange in aqueous solution under solar irradiation. Herein, mechanisms for the formation of different shapes of ZnO nanostructures decorated on graphene and their enhancement towards surface and photoactivity were discussed in details. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.