### Galvanostatic. Charge-Discharge (GCD):

Constant Current Charging/Discharging (CCCD) tests, also known as Galvanostatic charge/discharge (GCD) most important tests, are frequently used to assess energy storage systems and materials, such as those used in electrochemical capacitors (ECs). We have computed the specific capacitance and cyclic stability of the built device at various current densities using GCD measurements (Bugeaud, Corvaja, & Zannier, 2003).

Applying constant positive and negative, using negative
currents, a material or system is charged and discharged up to a certain
potential limit; this process is frequently done numerous times (De Levie,
1964).

Figure 4.6 GCD graph of Al doped ZnS

The shapes of GCD curves for Al doped ZnS nanosheets
confirmed the faradic reaction and clearly shows in figure. Also, these results
compatible with CV curve results. The excellent reversible redox nature of our
electrode is demonstrated by the comparatively symmetric shape of GCD curves.
It is important to note that as the current densities increase, the GCD curves
become more slope, and hence current density and curve are not linearly with
each other indicating features of the capacitor at high current densities and
battery-type behavior at low current densities. We can calculate mass specific
capacitance from GCD by using above following equation. We have found high
value of specific capacitance it

C = IÃ— Î” t

m Ã— Î” v

In above equation â€•Câ€– shows specific capacitance, â€–vâ€–
represents the optional of discharges â€•Iâ€– represent discharge current, â€•mâ€–
represents electroactive material mass and â€•t â€•discharge time (sec). GCD curves
are used to find specific capacitance at different values of current.

Sr.No I(A/g) t(sec) m(g) V(v) C(F/g)

1 2 2600 11.5 0.33 1370

2 5 800 11.5 0.32 1087

3 10 300 11.5 0.34 767

4 15 200 11.5 0.35 745

5 20 100 11.5 0.36 483

In above table the values of calculated specific capacitance
are as followed 1370 F/g, 1087 F/g, 767 F/g, 767 F/g, 745 F/g, 745 F/g and 483
F/g at different values of current densities 2 A/g, 5 A/g, 10A/g, 15A/g, and 20
A/g respectively. In above calculation it is clear that capacitance of
electrodes calculated at high current density which is most favorable for
supercapacitor practical application. ZnS nanosheets exhibit exceptional
performance due to their increased surface area, which enables ions to
facilitate the faradic redox process during the intercalation and
de-intercalation processes. High value of specific capacitance plays very
important role in energy storage devices because higher value of specific
capacitance more energy can be stored. Power density is directly linked with
specific capacitance when one increase other also increase so higher
capacitance means higher power density (Xu et al., 2014).

Reliability devices are more reliable and provide consistent
output voltage which is also helpful for prevention of sensitive devices.
Charging and discharging rate increase if specific capacitance is high
therefore it is more useful for those application where we need fast charging
and discharging (Ma et al., 2022). of devices also depends on capacitance;
higher capacitance means

### Conclusion of Nanotechnology:

- The need for energy storage devices increases as non-renewable energy sources are depleted and the world faces an energy crisis. Demands of energy storage devices increase day by day. Many energy storage devices are under research and used in daily life. Most common used energy storage devices are batteries, fuel cell, capacitor and supercapacitor.
- The supercapacitor stands out because to its extraordinary qualities such a long cyclic liafe, quick charge and discharge rates, and high-power density. ZnS is most important material used in energy storage devices we apply different technique and derive results as follow.
- ZnS nanosheets are prepared in this experiment by using hydrothermal method. In this experiment titanium foil is used as a substrate.
- After morphology techniques done by using hydrothermal process, we get hexagonal structure of ZnS which shows maximum peaks at 28.63Âº at miller indices (111) confirmed by XRD. Sample showed minor different morphology due to Al doping but not at wide range. It is clear from SEM image average length of diameter of sample is 2, 2, 4 and 1 micro meter respectively.

### ZnS photocatalysts:

We used EIS technique for explanation of physical properties
such as chemical reaction rate and microstructural structure. In this technique
we used Nyquist and bode graph for analysis. Our graph showed the electric
behavior for the imaginary impedance for ZnS.

Galvanostatic charge/discharge (GCD) technique used for
checking the stability of material. We used GCD at different scanning rates and
find different values of specific capacitance most high value we observed is
1370 F/g and lowest value is 483 F/g at different value of scan rate. These
values clear that this material is most suitable for supercapacitor practical
applications. ZnS is most important for energy storage devices due to high
surface area. For redox reaction observation we used

CV curves for this purpose we used different scan rates
between 10 and 80 mV/s, and used optional window between 0.0 and 1.0 V for
examine the redox behavior, illuminating the typical nature of uniform ZnS
nanosheets. CV peaks of ZnS shows unique capability of nanosheets. Capacitance
tests of ZnS are performed by using CV and GCD. CV curves are completely
explained faradic reactions. CV curve are successfully explained the batter
rate capacity of ZnS nanosheets.

From above discussion we concluded that ZnS is most
important material for energy storage devices. ZnS shows high value of specific
capacitance. ZnS has the advantage of increasing energy density, or the amount
of energy that can be stored per unit of volume, in energy storage devices. As
a result, a smaller device can store more energy, making it more portable and
compact.