Excellent capacitive performance of a three-dimensional hierarchical porous graphene/carbon composite with a superhigh surface area

Abstract

Three-dimensional hierarchical porous graphene/ carbon composite was successfully synthesized from a solution of graphene oxide and a phenolic resin by using a facile and efficient method. The morphology, structure, and surface property of the composite were investigated intensively by a variety of means such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). It is found that graphene serves as a scaffold to form a hierarchical pore texture in the composite, resulting in its superhigh surface area of 2034 m 2 g 1 , thin macropore wall, and high conductivity (152 Sm 1 ). As evidenced by electrochemical measurements in both EMImBF 4 ionic liquid and KOH electrolyte, the composite exhibits ideal capacitive behavior, high capacitance, and excellent rate performance due to its unique structure. In EMImBF 4 , the composite has a high energy density of up to 50.1 Wh kg 1 and also possesses quite stable cycling stability at 100 8C, suggesting its promising application in high-temperature supercapacitors. In KOH electrolyte, the specific capacitance of this composite can reach up to an unprecedented value of 186.5 Fg 1 , even at a very high current density of 50 A g 1 , suggesting its prosperous application in high-power applications.