Conducting polymer nanostructures: template synthesis and applications in energy storage

Abstract

Conducting polymer nanostructures have received increasing attention in both fundamental research and various application fields in recent decades. Compared with bulk conducting polymers, conducting polymer nanostructures are expected to display improved performance in energy storage because of the unique properties arising from their nanoscaled size: high electrical conductivity, large surface area, short path lengths for the transport of ions, and high electrochemical activity. Template methods are emerging for a sort of facile, efficient, and highly controllable synthesis of conducting polymer nanostructures. This paper reviews template synthesis routes for conducting polymer nanostructures, including soft and hard template methods, as well as its mechanisms. The application of conducting polymer mesostructures in energy storage devices, such as supercapacitors and rechargeable batteries, are discussed.

Keywords: conducting polymers; nanotubes; nanowires; polyaniline; polypyrrole; template synthesis.

Figure 1.

a) Schematic diagram of the microemulsion fabrication of Polypyrrole hollow nanospheres, and their carbon derivative. b-e) transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images of Polypyrrole nanoparticles and hollow spheres: b) soluble Polypyrrole nanoparticles; c) linear Polypyrrole/crosslinked Polypyrrole core/shell nanoparticles; d) Polypyrrole nanocapsules; e) carbon nanocapsule derivative. Reproduced with permission from The Royal Society of Chemistry [49].

Figure 2.

a) Schematic diagram of Polypyrrole nanotube fabrication using reverse microemulsion polymerization. b) transmission electron microscopy (TEM) image of Polypyrrole nanotubes. Reproduced with permission from The Royal Society of Chemistry [52].

Figure 3.

Conductive polymer nanotube junctions and their aggregated dendrites fabricated using non-templating (self-assembly) method: a-c) transmission electron microscopy (TEM) and d) scanning electron microscopy (SEM) image of Polyaniline nanotube junctions; e) SEM image of Polypyrrole dendrite. Reproduced with permission from Wiley-VCH Verlag [60].

Figure 4.

Polyaniline hollow particle fabricated by the hard template method. a) Scanning electron microscopy (SEM) image of Octahedral Cu₂O crystal template; b) Polyaniline hollow particle replicates. Reproduced with permission from Wiley-VCH Verlag [77].

Figure 5.

Transmission electron microscopy (TEM) image of the conductive polymer nanotubes fabricated using the AAO template. Reproduced with permission from The International Society of Electrochemistry [80].

Figure 6.

Scanning electron microscopy (SEM) images of a) cryptomelane-phase manganese oxide template, and b) resultant polyaniline nanotubes. The inset of (b) is a transmission electron microscopy (TEM) image of the polyaniline nanotubes. c) Schematic illustration of the formation mechanism of the polyaniline nanotubes. The scale bar is 1 μm. Reproduced with permission from Wiley-VCH Verlag [27].

Figure 7.

Transmission electron microscopy (TEM) images show the structural evolution during the conversion from cryptomelane phase manganese nanowires to polyaniline nanotubes after: a) 60 s; b) 180 s; and c) 480 s. d) the magnified image of the root region of (b). e), f) HRTEM (high-resolution TEM) images indicate the formation of polyaniline (shell)/manganese oxide (core) composite tube in the corrosive etching of manganese oxide. The scale bar is 1 μm. Reproduced with permission from Wiley-VCH Verlag [27].

Figure 8.

Schematic illustration of the proposed microzone galvanic cell reaction that occurs during the conversion from manganese oxide wire to polyaniline nanotube. a) The aniline was polymerized on a manganese oxide nanowire surface. b) The hollow structure developed mainly through the micro-zone galvanic-cell reaction mode. c) The homogeneous polyaniline tube was finally formed because the whole surface of the polyaniline (Polyaniline) thin film was almost equipotential in the micro-zone galvanic-cell reaction. Reproduced with permission from Wiley-VCH Verlag [27].

Figure 9.

a) Schematic illustration of the formation mechanism of MnO₂/PEDOT composite nanowires; b) Scanning electron microscopy (SEM) image of MnO₂/PEDOT coaxial nanowires (0.75 V). c) Transmission electron microscopy (TEM) image from a single coaxial nanowire (0.75 V). d and e) Energy Dispersive Spectroscopy (EDS) maps of S and Mn from the boxed area in Figure 9c. Reproduced with permission from The American Chemical Society [115].

Figure 10.

a) The illustration of the synthetic route of Wang to well structured conducting polymers and mesoporous carbon. b) SEM image of mesoporous carbon product; c, d) TEM images of mesoporous carbon seen from the [001] and [100] directions; e) SEM image of POLYANILINE/mesoporous carbon product; f, g) TEM images of POLYANILINE/mesoporous carbon at different magnifications. Reproduced with permission from Wiley-VCH Verlag [15].

Scheme 1.

Illustration of the template synthesis of conducting polymer nanostructures: 1) soft template method and 2) hard template method. Method 1) includes a) microemulsion and reversed-microemulsion synthesis; and b) non-template (self-template) synthesis, in which monomer or oligomer forms structural micelles by themselves. Method 2) includes: c) physical templating against existing nanostructure of particles; d) structural replicate against nanochannels, the method is firstly raised by Prof. C. R. Martin; e) reactive template method, which clone nanostructures by the chemical reaction between template and monomers. Background of the picture is the art “tree-of-life”, by Tim Parish in 2008, which is available at: http://torrancepubliclibrary.files.wordpress.com/2009/08/tree-of-life-web.jpg.