The importance of raw graphite size to the capacitive properties of graphene oxide

Carbon-based materials have been widely used in energy storage and conversion devices. Among them, graphene oxide (GO) holds much promise for supercapacitor applications due to its high-capacitance, low-cost, etc. Nevertheless, intrinsic characteristics related to the capacitive properties of GO are far from being fully understood. Little attention has been paid to the size effect of raw graphite on the electrochemical characteristics of GO. In order to investigate the relationship between raw graphite size and the capacitive properties of GO, electrochemical performances of GO, prepared from raw graphite of three different sizes using a modified Hummer's method, were compared. Experimental results indicated that the capacitance of a GO electrode was enhanced with the increasing size of the raw graphite. The GO electrode prepared with the largest size of raw graphite achieved a specific capacitance as high as 94.4 F g^-1 at 0.1 A g^-1 due to a medium-sized specific surface area and smaller charge transfer resistance. It is concluded that more attention should be paid to the prevention of agglomeration or even restacking of the graphene-based material after the heat drying of graphene-based solutions because of residual intercalated water molecules, which contribute to strong hydrogen bonding interactions between layers.