Double-Layer Specific Capacitance Characterization Using Three-Electrode Cell

1 Double-Layer Specific Capacitance Characterization Using Three-Electrode Cell 

Cyclic voltammogram of mesoporous carbon coated glassy carbon electrode surface (0.2 cm ), recorded in N2-purged 0.5 M H2SO4 solution at 23°C and ambient pressure. Carbon loading = 100 ]ig.cm . Potential scan rate = 50 mV.S . Source Nicholson, R. S. and I. Shain. 1964. Analytical Chemistry, 36, 706-723. With permission.) 

Combining Equations (7.6) and (7.4), the specific capacitance of fhe carbon-based double-layer material at the electrode potential E can be expressed as 

Practically, this charge quantity can be obtained easily by measuring the areas under the CV trace scan or by using CV software. The specific capacitance can be obtained by 

Note that both Equations (7.8) and (7.11) are obtained from data collected during forward potential scanning. The same calculation can also be carried out 

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For characterizing pure double-layer supercapacitors, CV has been identified as the most reliable technique. Figure 7.6 shows the CVs recorded from a mesoporous carbon layer using a conventional three-electrode cell [5]. Note that the label on the left Y-axis is "specific current," which is the current (A) divided by the weight of carbon particles loaded on the electrode surface (g). The label on the right Y-axis is "specific capacitance," which is the specific current (A) divided by the potential scan rate (V.s" ). As discussed in Chapter 2, specific capacitance can be expressed as... 

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