Reduced graphene oxide (rGO) flakes were supersonically sprayed onto a copper substrate, which was used to enhance the heat transfer between the cooling liquid and heat source in pool boiling. The results show that both the critical heat flux at which film bubbles are formed and the effective heat transfer coefficient increased substantially. The surface temperature of the heat source decreased substantially during efficient heat transfer. The higher wettability of the rGO film increased the cohesion of the cooling liquid with the heated surface. The roughened surface of the rGO film also facilitated the formation of small-scale bubbles that enhanced mixing and thus increased the rate of heat transfer. The rGO film was characterized using scanning electron microscopy, atomic force microscopy, and optical profiling. (C) 2016 Elsevier Ltd. All rights reserved.