Scanning electron microscopy (SEM) images reveal that the
freeze-dried aerogel consists of carbonaceous nanofibers selfassembled
into a porous, interconnected, 3D framework (Fig. 1b).
High-magnification SEM and transmission electron microscopy
(TEM) observations indicate that these nanofibers with a diameter
of ca. 140 nm are highly interconnected with large numbers of junctions
(see Supplementary Information, Fig. S1 and Fig. S2). The
3D network of the nanofibrous aerogel can survive well even after pyrolysis at a high temperature. However, the volume of obtained
CNF aerogel shrank to ca. 50% of that of the original carbonaceous
nanofiber aerogel, while the fiber diameter decreased to ca. 125 nm
(Fig. 1c), owing to evaporation of some volatile species during the
pyrolysis process.