Areal Capacitance

Recently, Zhang et al. [123] have demonstrated a flexible composite membrane of reduced graphene oxide and pol5T)5n role nanowire [rGO-PPy-NWs] via in situ reduction. A S5mimetric supercapacitor has been fabricated by direct coupling of two membrane electrodes, without the use of any binder or conductive additive. The supercapacitor achieved a large areal capacitance [175 mF/cm ] and excellent cycling stability. The in situ reduction of GO in the composite dispersion with PPy-NWs renders the formation of the rGO-PPy composite foam via self-assembly, as shown in Fig. 7.11. 

Donough, J. et al. (2009). Carbon nanofiber supercapacitors with large areal capacitances. Applied Physics letters, 95, 243109-243 111. 

The areal capacitance of carbon electrodes depends strongly on carbon type. Graphite is the simplest case to consider, because it lacks surface functionalities. In this special case, the areal capacitance may be represented, to a first... 

For a tuiiform field, the continuum level approximation for the difference between electrical energies of water-filled (1) and empty (e) pores, treated as capacitors with areal capacitances Cg = olD and Ci = s q/D, gives [7]... 

The areal capacitances of the pore walls (CdP ), falling in the range 120 to 230 mF cm 2, were on the same order as that of the 1-min direct-etched diamond surface (see Table 19.1). This capacitance enhancement for the plasma-etched surfaces is due to contributions from oxygen-containing functional groups and... 

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). 

Studies on the woven fabrics using plain weaves made from high density polypropylene monofilaments were carried out using ASTM D150 standard method [46]. Four fabrics were used, each of which had different filament diameter, yam spacing, thickness and areal mass density. Each of these fabrics was kept between the capacitor plates and the corresponding volume fraction was calculated from the fabric areal density, density of the fiber and the electrode gap. The effective permittivity of the capacitor system with the fabric was calculated from the recorded capacitance value and the over-all capacitor dimensions using... 

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