Electrochemical polymerization supercapacitors

Regarding the application in supercapacitor, the flexible PANI nanotube arrays with high and stable specific capacitances were prepared via electrochemical polymerization. The specific capacitances increased with decreasing wall thicknesses (Wang et al., 2012). A three-dimensionally hierarchical porous PPy hydrogel with various mechanical and electrochemical properties are fabricated by controlling the ratio of phytic acid to pyrrole monomer in the synthetic process. The solid-state supercapacitor showed a weight specific capacitance of 380 F g and areal specific capacitance of 6.4 F cm at a mass load of 20 mg cm(Shi et al., 2014). 

Some methods have been attempted to improve the capacitance and conductivity of carbon-based supercapacitors. For example, fabrication of a CP/graphite fiber composite with PPy has been done by using electrochemical polymerization of Py on the surface of graphite fiber and shows higher capacitance and conductivity. ... 

Prototypes of such supercapadtors of small geometric areas have been developed [126, 127]. 3-MethylPT and poly(dithieno[3,4-b 3, 4 -d]thiophene) have been grown galvanostatically on carbon paper electrodes by electrochemical polymerization of the appropriate monomers. The properties of studied supercapacitors with these materials are comparable to common carbon supercapadtors in the case of the first mentioned polymer and appear to be better in the case of the second polymer [125]. 

Strain [120]. Recently, it was shown that even better textural properties may be obtained when using the in situ polymerization of styrene sulfonate [121]. Taking advantage of the large microporous volume, the carbons were studied as electrochemical supercapacitors, and capacitance of 100 F/g was obtained for carbons obtained from PSS/LDH in an acidic medium. 

Since the appearance of the redox [ii, iii] and conducting [iv] polymer-modified electrodes much effort has been made concerning the development and characterization of electrodes modified with electroactive polymeric materials, as well as their application in various fields such as -> sensors, actuators, ion exchangers, -> batteries, -> supercapacitors, -> photovoltaic devices, -> corrosion protection, -> electrocatalysis, -> elec-trochromic devices, electroluminescent devices (- electroluminescence) [i, v-viii]. See also -> electrochemically stimulated conformational relaxation (ESCR) model, and -> surface-modified electrodes. 

Hashmi and Upadhyaya compared the electrochemical properties of the electrochemically synthesized MnO /PPy composite electrodes, fabricated with different electrolytes, namely polymer electrolyte film (polyvinyl alcohol [PVA]-HjPO aqueous blend), aprotic liquid electrolyte (LiClO -propylene carbonate [PC]), and polymeric gel electrolyte (poly methyl methacrylate [PMMA]-ethylene carbonate [EC]-PC-NaClO ) [60]. The cell with aqueous PVA-H PO showed non-capacitive behavior owing to some reversible chemical reaction of MnO with water, while the MnO / PPy composite was found to be a suitable electrode material for redox supercapacitors with aprotic (non-aqueous) electrolytes. The solid-state supercapacitor based on the MnO /PPy composite electrodes with gel... 

The electrochemical method has two disadvantages compared to the method of chemical polymerization. One is that the electrochemical method is limited in terms of the mass production of composite electrodes. The other disadvantage is that the electrochemical method is not suitable for preparing controlled polymer films with thicknesses above 100 p.m, although it is suitable for preparing very thin films of polymer, if a thin polymer film with a very high specific capacitance per unit mass is converted to specific capacitance per unit area, this value is less than that for a carbon-based supercapacitor because of the small deposited polymer mass. ... 

The bulk of EAP-based supercapacitor work to date has focused on Type I devices. Polypyrrole (PPy, Figure 9.4C) has been studied [147,151-153] for this application, with specific capacitance values ranging from 40 to 200 F/g. Garcia-Belmonte and Bisquert [151] electrochemically deposited PPy devices that exhibit specific capacitances of 100-200 F/cm with no apparent dependence on film thickness or porosity extensive modeling of impedance characteristics was used. Hashmi et aL [153] prepared PPy-based devices using proton and lithium-ion conducting polymer electrolytes. As is often observed, electrochemical performance suffered somewhat in polymeric electrolytes single electrode specific capacitances of 40-84 F/g were observed with stability of 1000 cycles over a 1 V window. 

P. Soudan, P. Lucas, H.A. Ho, D. Jobin, L. Breau and D. Belanger, Synthesis, chemical polymerization and electrochemical properties of low bandgap conducting polymers for use in supercapacitors, J. Mater. Chem., 11, 773-782 (2001). 

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