The FE-SEM images of the obtained materials at different stages
are shown in Fig. 2. It can be seen that PPy nanoparticles show
regular sphere morphology and mono-dispersivity, and their particle
size is about 150 nm in diameter (Fig. 2a). For the as-prepared
HGO nanosheets, a typically curved, loose, plate-like morphology
can be observed (Fig. 2b). After reacting with VC at 80 C, HGO
nanosheets are reduced and self-assembled into HGA with interconnected
3D macroporous network, in which the pore sizes range
from sub-micrometer to several micrometers and their pore wall is
consisted of single or a few HG nanosheets (Fig. 2c). On the other
hand, the FE-SEM image of the as-prepared HGPA with a mass ratio
of PPy/HGO ¼ 0.75 shows an interconnected and stable 3D porous
network, which consists of the crinkly HG nanosheets and PPy
nanoparticles with a diameter of 150 nm embedded between the
HG nanosheets (Fig. 2d). PPy nanoparticles embedded between the
HG nanosheets further prevent the restacking of HG nanosheets,
and the formed pore framework is favorable for shortening the ion
pathway and enhancing ion kinetics. Similar morphology is also
observed for sample GPA-0.75 (Fig. 2e)