Metal Oxide Supercapacitors

The specific capacitance C, energy density E, and corresponding power density P are defined by the following equations [4] 

Ideal supercapacitor behavior with large specific capacitance ( = 350Fkg ) of amorphous V2O5 nH20 in aqueous solution containing KCl with optimized pH has 

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In spite of the research progress still continuing for the development of graphene composites for industrial applications, these materials have already been explored for a range of applications in different fields such as optoelectronic devices (mostly use semiconductor and quantum dots), energy storage (Li-ion batteries, which use transition metal oxides supercapacitors, which use transition metal oxide and polymers fuel cells, which use metal NPs and polymers solar cells, which use metal oxide and polymer), sensors (use metal, oxide and polymer) and biomedical applications (use protein, DNA, polymers, etc.). The details have already been explained in their respective sections in this review chapter. 

C. Lin, J. A. Ritter, and B. N. Popov, Development of Carbon-Metal Oxide Supercapacitors from Sol-Gel Derived Carbon-Ruthenium Xerogels, J. Electrochem. Soc., 146, pp. 3155-60, 1999. 

Lin C, Ritter JA, Popov BN (1999) Development of carbon-metal oxide supercapacitors liom Sol-Gel derived carbon-mthenium xerogels. J Electrochem Soc 146 3155... 

Faradaic in nature and therefore is different farm Pseudocapacitance usually originates from electrosorption (specific adsorption) processes and related partial electron transfer or surface charging (Section 5-5). On metal oxide "supercapacitor" types of electrodes (such as iridium and ruthenium oxides) possessing several oxidation states, pseudocapacitance originates from potential dependence of multiple oxidation/reduction couples that are active on the surfaces of the materials. Another coiiunon source of pseudocapacitance is charging-discharging of redox-active polymers such as polyaniline and polypyrrole. 

In supercapacitors, apart from the electrostatic attraction of ions in the electrode/electrolyte interface, which is strongly affected by the electrochemically available surface area, pseudocapacitance effects connected with faradaic reactions take place. Pseudocapacitance may be realized through carbon modification by conducting polymers [4-7], transition metal oxides [8-10] and special doping via the presence of heteroatoms, e.g. oxygen and/or nitrogen [11, 12]. 

The synthesis of nanostructured carbon using aliphatic alcohols as selfassembling molecules has demonstrated that this strategy can be extended beyond metal oxide-based materials [38]. Recently, we have reported the synthesis of a novel carbon material with tunable porosity by using a liquid-crystalline precursor containing a surfactant and a carbon-yielding chemical, furfuryl alcohol. The carbonization of the cured self-assembled carbon precursor produces a new carbon material with both controlled porosity and electrical conductivity. The unique combination of both features is advantageous for many relevant applications. For example, when tested as a supercapacitor electrode, specific capacitances over 120 F/g were obtained without the need to use binders, additives, or activation to increase surface area [38]. The proposed synthesis method is versatile and economically attractive, and allows for the precise control of the structure. 

Cottineau T, Toupin M, Delahaye T, Brousse T, Belanger D. Nanostructured transition metal oxides for aqueous hybrid electrochemical supercapacitors. Applied Physics 2006 A82 599-606. 

Electrodeposition is a unique, versatile technique for fabrication of metal oxide, polymer, and composite electrodes for electrochemical supercapacitors. Composition, crystal structure, and morphology of the deposits can be easily manipulated by adjusting the electrodeposition parameters to achieve improved capacitive behavior. Current progress, however, is far from the commercial expectations for electrochemical supercapacitors. 

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