Partially reduced graphene oxide nanosheet (prGON)/poly(sodium 4-styrenesulfonate) (PSS) composite with very high specific capacitance were prepared. Graphene oxide nanosheets (GON) were firstly partially reduced by a weak reducing agent, and PSS was attached to prGON through π–π stacking, acting as a spacer to prevent prGON from agglomeration. Otherwise, PSS could only bind GON through combining with the hydroxyl groups on GON. The prGON/PSS composite was then potentiostatically reduced at a constant potential. During the electrochemical reduction, the carbonyl groups on the prGON/PSS composite were gradually reduced to other oxygen functionalities instead of being removed. The redox-active oxygen-containing groups on the electrochemically reduced prGON/PSS composite were stable in the potential scanning range, and introduced pseudo-capacitance. The specific capacitance of the prGON/PSS composite after electrochemical reduction reached 367.2 F/g in 1 M KCl aqueous solution at the scanning rate of 5 mV/s, and retained its 93.8% capacitance after 1600 cycles. The superior capacitance performance can be ascribed to the outstanding intrinsic properties of graphene, the PSS spacer attached to prGON through π-π stacking, and the pseudo-capacitance introduced by the oxygen-containing groups.

Three-dimensional ordered macroporous (3DOM) carbon nanotube (CNT)/polypyrrole (PPy) composite electrodes for supercapacitor application were prepared through cyclic voltammetric copolymerization from a solution containing both acid-treated CNTs and pyrrole monomers. A self-assembled SiO2 colloidal crystal was used as the sacrificial template. After electrochemical copolymerization, the template was removed, and a 3DOM CNT/PPy composite electrode was obtained. The specific capacitance of the composite reached 427 F g–1 at the scanning rate of 5 mV s–1, and it is calculated that ion diffusion contributed approximately 30% to the specific capacitance of the composite. A mathematical model of mass transport was proposed to evaluate the ion diffusion capability on the surfaces of 3DOM, nanoporous, and planar films. The calculation results showed that the flux (i.e., ion flux per unit length) of 3DOM film was larger than that of planar film, while the flux of nanoporous film was close to that of planar film. The model indicates that 3DOM film is favorable for ion transportation, while nanoporous film does the opposite. The model partially explains the reason why the specific capacitance of the prepared 3DOM CNT/PPy composite is far above the specific capacitance values of other reported CNT/PPy composites, even the nanoporous CNT/PPy composite.