Introduction: Hierarchical Nanostructures for Energy Devices - Hierarchical Nanostructures for Energy Devices - page 4

improve light absorption due to the increased optical path as well as add-
itional light trapping through reduced reflection and multi-scattering in
comparison to 1D nanowire arrays, which are beneficial for solar energy
harvesting applications. 5 The high surface area can also increase surface
activity and electrolyte infiltration in supercapacitors and batteries, and the
direct charge carrier transport pathway in both the trunks and branches
boosts the charge collection eciency. 5 These fascinating properties of 3D
branched nanowire structures have therefore stimulated widespread interest
in fabricating them. The bottom-up approaches, including vapour phase and
solution-based routes, allow fabrication of a wide variety of 3D branched
nanowires with diverse functions. 5
The appropriate electronic, ionic, and electrochemical requirements for
such devices may now be assembled into nanoarchitectures on the bench-
top through the synthesis of low density, ultraporous nanoarchitectures that
meld a high surface area for heterogeneous reactions with a continuous,
porous network for rapid molecular flux, for example, the three-dimensional
design for batteries in Figure 1.2. Such nanoarchitectures amplify the nature
of electrified interfaces and challenge the standard ways in which electro-
chemically active materials are both understood and used for energy storage.
An architectural viewpoint provides a powerful metaphor to guide chemists

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.

Figure 1.2 Three-dimensional designs for batteries.
(Adapted from ref. 8; reprinted with permission. Copyright 2004,
American Chemical Society.) Reproduced by permission of The Royal
Society of Chemistry. 4