A novel method has been developed to synthesize graphene-ZnO composite as a highly efficient catalyst by reduction of graphite oxide and in situ deposition of ZnO nanoparticles by chemical reduction reaction. The graphene-ZnO catalyst is capable of complete degradation of rhodamine B under exposure to natural sunlight. Further, the catalytic efficiency of graphene-ZnO catalyst was enhanced by sensitizing with cobalt phthalocyanine. The formation of graphene-ZnO photocatalyst and its further sensitization with cobalt phthalocyanine was characterized using UV-vis, ATR-IR and Raman spectroscopy, powder XRD and thermogravimetric analysis. The morphology of both graphene-ZnO and graphene-ZnO-CoPC catalysts was analyzed using scanning and transmission electron microscopes. (C) 2014 Elsevier Inc. All rights reserved.