Electrochemical capacitance enhancement

Tanahashi, I. 2005. Capacitance enhancement of activated carbon fiber cloth electrodes in electrochemical capacitors with a mixed aqueous solution of H2SO4 and AgNOj. Electrochemical and Solid-State Letters 8 A627-A629. 

Shimooka T, Yamazaki S, Sugimoto T, Jyozuka T, Teraishi H, Nagao Y, Oda H, Matsuda Y, Ishikawa M (2007) Capacitance enhancement of aqueous EDLC Systems by electrochemical treatment. Electrochemistry 75 273-279... 

Lu X, Dou H, Yuan C, Yang S, Hao L, Zhang F et al (2012) Polypyrrole/carbon nanotube nanocomposite enhanced the electrochemical capacitance of flexible graphene film for supercapacitors. J Power Sources 197 319-324... 

Wang J, Wu Z, Yin H, Li W, Jiang Y (2014) Poly (3, 4-ethylenedioxythiophene)/MoS2 nanocomposites with enhanced electrochemical capacitance performance. RSC Adv 4 56926-56932... 

In recent several years, super-capacitors are attracting more and more attention because of their high capacitance and potential applications in electronic devices. The performance of super-capacitors with MWCNTs deposited with conducting polymers as active materials is greatly enhanced compared to electric double-layer super-capacitors with CNTs due to the Faraday effect of the conducting polymer as shown in Fig. 9.18 (Valter et al., 2002). Besides those mentioned above, polymer/ CNT nanocomposites own many potential applications (Breuer and Sundararaj, 2004) in electrochemical actuation, wave absorption, electronic packaging, selfregulating heater, and PTC resistors, etc. The conductivity results for polymer/CNT composites are summarized in Table 9.1 (Biercuk et al., 2002). 

ZnO [79] have been used in ECs. These hybrids all show enhanced electrochemical performance in terms of the high reversible capacity of LIBs or specific capacitance of ECs, rate capability, and cycling performance. 

Recent interest in this topic [102] has been tremendous, spurred not only by the opportunity (and indeed desperate need ) to further enhance the performance of batteries but, especially so, to develop novel supercapacitors [68], Among the 41 papers published only in 2007 (through October)—a remarkable number, indeed—and identified as directly relevant to this section of the chapter, 24 were devoted primarily to carbon capacitance issues [71,95,103-124], 7 to redox behavior [125-131], 6 to electrosorption [132-137], and the others to more general electrochemical properties and behavior. 

One practical and one fundamental question are of interest here (a) How much charge can be stored in carbons (b) How does the amount of charge stored depend on the nature of the carbon and thus on its surface chemistry Their answer(s) should lead to the resolution of an apparent contradiction that is implicit in the following statements from recent authoritative reviews [T]he preferred carbon materials [for electrochemical capacitors] should be free from... surface quinonoid structures that can set up self-discharge processes that must be minimized [68] [s]ubstitutional heteroatoms in the carbon network (nitrogen, oxygen) are a promising way to enhance the capacitance [95],... 

As a final note concerning solvent effects, amphiphilic alcohols added to hydro-phobic electroactive n-alkanethiol SAMs in aqueous solution appear to aggregate on the monolayer surfaces, decreasing the capacitive envelope and enhancing the barrier properties [109, 110]. However, the formal potentials of the redox couples are shifted positively, and the electrochemical reversibility is decreased. This effect had previously been used by Becka and Miller to determine the pinhole current in the presence of a freely diffusing redox probe (see above) [96]. 

X. Zou, S. Zhang, M. Shi, and J. Kong, Remarkably enhanced capacitance of ordered polyaniline nanowires tailored by stepwise electrochemical deposition, J. Solid State Electrochem., 11, 317-322 (2007). 

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