Cobalt sulfide (CoS)/graphene composites are prepared by a facile one-pot hydrothermal method in the presence of graphene oxide and used as a low-cost substitute for Pt to fabricate the counter electrode in dye-sensitized solar cells. TEM, SEM and AFM characterizations show that CoS nanoparticles are highly dispersed on the surface of graphene nanosheets. This unique nanostructure affords a promising synergistic effect on electrocatalytic performance for the iodide/triiodide redox reaction. Electrochemical impedance spectroscopy and Tafel polarization analyses confirm that the CoS/graphene composite indeed provides simultaneously superior electrocatalytic activity and enhanced electrical conductivity as the counter electrode for dye-sensitized solar cells. Under an illumination of AM 1.5 simulated solar light (100 mW cm(-2)), the dye-sensitized solar cell based on the CoS/graphene composite counter electrode achieves a conversion efficiency of 7.08%, which is comparable to that of the cell based on Pt electrode and much higher than those of the devices with CoS and graphene electrodes. (C) 2014 Elsevier B.V. All rights reserved.