The real capacitance is computed according to equation C′ = [-Z″]/[ω|Z|2].
The introduction of the concept of Constant Phase Element into the equivalent circuit model gave a fit in good agreement with the experimental data and implied the influence of a fractal interface on the real capacitance.
Open image in new window Fig. 8 a Nyquist impedance plots, b the relationship between the real capacitance and frequency, c the relationship between the imaginary capacitance and frequency, and d the variation of the relaxation time with the heating temperature.
According to the results of the fitting of the charge-discharge measurements and of the modified Randles model, values of real capacitances up to thousand times larger than the theoretical capacitance of a similar capacitor with a continuous layer dielectric are found.
Despite these appealing features, the real specific capacitance obtained from various Co3O4 nanostructures [18, 19, 20] is still far below the theoretical value, which may be attributed to its intrinsic semiconducting characteristic [21].
The sensor elements are fabricated as meso-PSi (pore sizes <50 nm, pore thickness ∼7 μm), with Ag metallic contacts made exclusively at the backside of bulk silicon, and ethanol sensing is achieved by measurement of the real-time capacitance and conductance.
Real-time capacitance measurements (Cm) were performed using the Lock-in amplifier Patchmaster software (HEKA) by applying a 1 kHz command sine wave (amplitude 20 mV) at holding potential (-80 mV) before and after the pulse experiment, as previously described (Vincent et al., 2014).
Recently, using real-time capacitance measurements to identify saturable pools of vesicles, a superlinear release component requiring recruitment of vesicles to release sites has been identified, leading to the suggestion that Ca2+-dependent vesicle trafficking is responsible for this movement, which is required for hair cell synapses to maintain high rates of sustained vesicle fusion [ 125].
The electrochemical impedance spectroscopy (Nyquist and Bode) analysis together with the frequency dependent capacitance (real and imaginary) studies confirmed the ideal capacitive nature of the RuS2 supercapacitor.
Here, C′ is the real part of capacitance representing the energy storage component and C″ the imaginary part represents the resistive losses in the storage process.
A typical specific capacitance, real power and energy density of the cell with 10% replacement of water by glycol were ∼21 F.g−1, 0.7 kW.kg−1 and 11 Wh.kg−1 respectively which is significantly higher than the aqua gel based cell (∼22 F.g−1, 0.55 kW.kg−1 and 6 Wh.kg−1).
