3.7. Electrochemical analysis—supercapacitor applications
Fig. 8 shows the cyclic voltammetry (CV) and charge-discharge
curve for T-GNS and HB-GNS with 0.5 M H2SO4 as electrolyte.
Fig. 8(a) shows the CV curves for T-GNS in an optimized potential
window range (0.4 to 0.04 V) at different scan rates from 5 to
50 mV/s. The CV curves are nearly rectangular in shape, it show
that the T-GNS working electrode behaves like electric double layer
capacitor (EDLC). The current increases with increase in scan rate
as observed in CV curves.
Fig. 8(b) shows the cyclic voltammetry of HB-GNS which clearly
exhibit a rectangular shape with current switching at two pair of
potentials for HB-GNS with optimized potential window (0.6 to0.05 V). The rectangular shape was retained for the all scan rates
5–50 mV/s. Cyclic voltammetry (CV) reveals that B-GNS draw the
perfect rectangular shape than T-GNS due to the switching of
current. The CV curve confirms the EDLC behavior of the boron
doped graphene nanosheets (HB-GNS).
The galvanostatic charge-discharge analysis was performed for
T-GNS and HB-GNS materials and their specific capacitance (Csp)
was calculated with different current densities using the following
equation (Eq. (A.1))
C ¼ I Dt
m DV ðA:1Þ
Where, C—the specific capacitance (F g1) for single electrode,
I—the charge–discharge current (mA), Dt—the discharge time (s),
DV—potential window during charge–discharge, and m—the mass
(mg) of the active material within the single electrode.
Fig. 8(c & d) shows the charge-discharge curves for Potential (V)
versus discharge time (Dt) at different current densities of T-GNS
and HB-GNS materials. Fig. 8(c) Shows the galvanostatic chargedischarge of T-GNS samples at different current densities (1–4 A/g).
The calculated specific capacitances values from the Eq. (A.1) are
52 F/g, and 43 F/g, 28 F/g and 20 F/g for different current density
values 1 A/g, 2 A/g, 3 A/g respectively. The charge-discharge curves
are near triangular shaped with double layer capacitance behavior.
The T-GNS gives maximum specific capacitance of 52 F/g at 1 A/g.
Fig. 8(d) shows the galvanostatic charge-discharge test of B-GNS
samples to investigate its supercapacitor behavior. The specific
capacitance of B-GNS electrode materials was calculated at
different current densities (1–4 A/g) in discharge time curve,