PANI Electrochemical Supercapacitor

PANI is one of the promising materials in supercapacitors due to its high capacitive characteristics, low cost, and easy synthesis. The materials in nanosize form with high surface area and high porosity give the best performance as electrode materials for supercapacitors because of their distinctive characteristics of conducting pathways, surface interactions, and nanoscale dimensions. The synthesis and capacitive characterization of high-surface-area nanomaterials, that is, nanotubes, nanowires, etc., have been carried out extensively in the past decades. Consequently, different indirect methods were used to synthesize nanosized PANI, such as template synthesis, self-assembly, emulsions, and interfacial polymerization.  

The CV current densities and the calculated specific capacitance value (Csp) of 775 F/g were obtained at a scan rate of 10 mV/s, whereas a Qp value of 562 F/g was obtained at a high scan rate of 200 mV/s. This decrease of 25% in the specific capacitance at high scan rates is much lower than in the case of metal oxides where a decrease of 50%-80% was reported between 10 and 200 mV/s. Moreover the CV current increases linearly with an increase in the scan rate (Fig. 7.2f]. This implies highly stable supercapadtive characteristics of the PANl nanowires.  

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Electronically conducting polymers (ECPs) such as polyaniline (PANI), polypyrrole (PPy) and po 1 y(3.4-cthy 1 cncdi oxyth iophcnc) (PEDOT) have been applied in supercapacitors, due to their excellent electrochemical properties and lower cost than other ECPs. We demonstrated that multi-walled carbon nanotubes (CNTs) prepared by catalytic decomposition of acetylene in a solid solution are very effective conductivity additives in composite materials based on ECPs. In this paper, we show that a successful application of ECPs in supercapacitor technologies could be possible only in an asymmetric configuration, i.e. with electrodes of different nature. 

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). 

Due to the outstanding electrical and electrochemical properties of CNT/PANI, composite materials have also been applied as anode for a microbial fuel cell [335], high performance supercapacitors [333,336,337], and as modified electrode for the reduction of nitrite [331]. 

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