Fig. 3a shows the nitrogen adsorption/desorption isotherms of
the carbon produced with the CVD growth time of 5 min and 10 min.
It is seen that their isotherms are quite similar to that of graphene
[12,13], i.e. type IV isotherms with a H2 hysteresis loop,indicating a
mesoporous structure.It is explained by their graphene-like
nanosheet morphology as shown in Fig. 1a and b,in which the pores
come from the overlapped stacking of the nanosheets, same to
graphene.With the CVD growth time increases to over 15 min, the
obtained carbon exhibit different isotherm shapes (Fig. 3b). The
sharp capillary condensation step at very high relative pressures (p/
p040.9) and the H1-type hysteresis loops indicate the existence of
large pores in the material,characteristic of the cores of the carbon
nanocages.