Electric Double-Layer Capacitance of Carbon Nanocages

We have carried out capacitive experiments on carbon nanocage (CNC) materials, which have highly ordered and uniform pores. The sizes of the opening pores in CNCs are approximately 5.6 nm, as measured from TEM images. CNC materials exhibit type IV nitrogen adsorption isotherms according to the IUPAC classification scheme along with hysteresis and BJH desorption pore size distributions of about 5.2 nm, with high BET surface areas of 1515 m(2).g(-1) and large pore volumes of 2.0 cm(3).g(-1). The density and specific surface area of the CNC thin film were 0.289 g.cm(-3) and 366 m(2).cm(-3), and those of the AC-A film, compared with that of the most popularly employed activated carbon, were 0.608 g.cm(-3) and 671 m(2).cm(-3) by the CV measurement, respectively. The gravimetric capacitance (ca. 200 F.g(-1)) for the CNC modified electrode is almost equal to that of the AC-A electrode; however, the volumetric capacitance of the CNC electrode (ca. 50 F.cm(-3)) is only half that of the AC-A electrode, suggesting that the pore spaces in the CNC material are much larger than those in AC-A, and large interfaces in these spaces are not favorable for EDLCs.