Chemistry Reference
In-Depth Information
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Figure 9.11
(a-e) CNT-graphene hybrid system. (a) Schematic of CNT growth from
catalyst nanoparticles supported on graphene nanosheets. (b-e) SEM
images of the CNT-graphene structure. (e) TEM image highlighting
catalytic growth of the CNTs with the Co catalyst nanoparticle embed-
ded at the tip. Reprinted from ref. 83 with permission. Copyright 2010,
John Wiley and Sons. (f-k) Co
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NW-graphene foam hybrid system.
(f) SEM image of the 3D interconnected graphene foam. (g, h, i) SEM
image of the hierarchical CoO
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NW-graphene foam structure. (j, k)
TEM images of the Co
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nanowires grown on the graphene surface.
Reprinted with permission from ref. 18. Copyright 2013 American
Chemical Society.
.
Chemical vapor deposition of CNTs on graphene layers requires well-
dispersed catalytic seeds to avoid undesirable agglomeration of the catalyst
nanoparticles at high temperatrues.
83
In contrast, seedless hydrothermal
synthesis of capacitive nanowires can enable the growth of dense nanowire
arrays at relatively low temperatures. Due to the low diffusivity of solution
precursors, supply of the precursor molecules should be facilitated via
relatively large transport channels for uniform growth of the nanowires. In
this regard, macro-/meso-porous carbon templates are plausible substrates
to build a 3D structure of capacitive nanowires based on the hydrothermal
method.
Dong et al.'s study exemplifies this capacitive nanowire (1D)-macro-/
meso-porous carbon (3D) hybrid system (Figure 9.11(f)-(k)).
18
They syn-
thesized pseudocapacitive Co
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nanowires by a hydrothermal method on a
3D graphene foam prepared from a Ni foam template by CVD. The produced
graphene foam was conductive and light in weight, and served as an excel-
lent 3D scaffold for the growth of the Co
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O
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nanowires. The reported
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