**7. Conclusion**

*Colloids - Types, Preparation and Applications*

**S.No. Aqueous electrolyte DC** 

17 sodium dodecyl

18 Sodium Dodecyl Sulphate (SDS)

23 ionic liquids in acetonitrile

**Table 2.**

sulphate (SDS)

**6. Application of colloidal graphene**

*Recent electrolytes used for the electrochemical exfoliation of graphene.*

21 sodium saccharin 2 V to

shown in **Figure 5**.

The colloidal dispersion of graphene produced by the electrochemical exfolia-

The performance of the flexible energy storage devices is measured by the CV Curves [8]. Further, the type of the gel electrolyte changes the shape of the CV curve measured and hence the performance of the energy storage device.

*Schematic diagram of the graphene based flexible energy storage device structure.*

tion method is ideal for the preparation of the graphene based flexible paper electrodes. For this, colloidal graphene is coated using brush coating method on A4 paper and dried. These graphene based flexible paper electrodes are used for the preparation of the flexible energy storage devices [8]. First a gel electrolyte is prepared by using PVA (polyvinyl alcohol) and water [34], then two graphene based paper electrodes are joined using this gel electrolyte in between electrodes. Later, two aluminum foils are joined to form the contacts with these electrodes for taking various measurements of these flexible energy storage devices (**Figure 4**). The actual fabricated flexible energy storage device using colloidal graphene is

**Voltage**

5 V to 9V

10 V

10 V-20 V

15 Sodium nitrate 10 V 0.1 M POOR [8] 16 Sodium perchlorate 10 V 0.1 M NO [8]

5 V 0.001 M to

19 TBA·H2SO4, NaOH 10 V 0.1 M Yes [29] 20 (NH4)2SO4,CH4N2S 10 V 0.1 M Yes [30]

22 NaCl (NaBr,NaI) 10 V 0.05 M Yes [32]

0.1 M

**Concentration Graphene /GO** 

**Exfoliation**

0.1 M to 0.01 M Yes [28]

0.1 M Yes [31]

0.1 M Yes [33]

Yes [27]

**Reference**

**38**

**Figure 4.**

This review article discusses electrochemical synthesis of colloidal graphene. Colloidal form of graphene is better than other forms of graphene available because of its solution route is easy to be used for the formation of graphene based electrodes. It is observed that electrochemical exfoliation of graphite is the simple, time saving and economical method for the production of colloidal form of graphene. Various aqueous electrolytes can be used for the electrochemical exfoliation of graphene from graphite. After the colloidal solution is obtained it is used for the preparation of the flexible paper electrodes which are suitable for the formation of flexible energy storage devices.
