**5. Recent works on electrochemical exfoliation of graphene**

Due to the various advantages of the electrochemical exfoliation technique in comparison to others, it has been extensively utilized recently for the preparation of graphene nanosheets for various applications. Recently industrial scale synthesis of few-layer graphene nanosheets have been synthesized where the electrochemical experiment shows that rate of graphene exfoliation increases with the higher concentration of intercalates and accordingly the colloidal conductivity changes [17]. In comparison to graphene, graphene oxide is more environment friendly because of the presence of oxygen-containing functional groups. In Comparison to standard Hummers' method for synthesis of GO, electrochemical exfoliation of graphite is considered facile and green with better crystallinity and higher oxidation degree [18].

**37**

*Recent Progress in the Electrochemical Exfoliation of Colloidal Graphene: A Review*

lytes used recently for the electrochemical exfoliation of graphene.

**Voltage**

3 V

10 V, 15 V

9 V, 10 V

7 Ammonium sulphate 9 V 0.1 M Yes [23]

 Potassium Sulphate 10 V 0.1 M Yes [25] Sulfuric acid 10 V 0.1 M Yes [26] Ammonium sulphate 10 V 0.1 M Yes [8] Sodium sulphate 10 V 0.1 M Yes [8] Potassium sulphate 10 V 0.1 M Yes [8] Ammonium chloride 10 V 0.1 M NO [8]

**Concentration Graphene /GO** 

3 V, 5V 0.5 M, 0.5 M Yes [19]

5 V 0.5 M Yes [20]

10 V 0.6 M Yes [21]

2 V 0.5 M, 0.05 M Yes [24]

**Exfoliation**

0.5 M to 2 M Yes [17]

0.05 M, 0.1 M Yes [18]

0.1 M Yes [22]

**Reference**

**S.No. Aqueous electrolyte DC** 

1 Sulfuric Acid 10 V,

4-styrenesulfonate)

2 Sodium sulfate, oxalate acid

4 poly(sodium

(PSS)

5 Mixture of Nitric acid and Sulfuric Acid

6 molybdate aqueous solution

8 Cobalt sulphate and Sodium sulphate

3 Sulfuric acid, Lithium sulphate

The role of electrolytes is very important in the quality of the graphene produced. The graphene synthesis mechanism in acidic (0.5 M H2SO4), neutral (0.5 M Li2SO4) is compared to non-destructive intercalation in organic electrolyte (1 M NaClO4 in acetonitrile) [19]. Another important advantage of electrochemical exfoliation is that it can be utilized for the synthesis of graphene from electronic waste because it is a great threat to the environment due to difficulty in recycling, difficulty in conversion of waste to useful materials. So, researchers have reported a facile and fast production method of electrochemical exfoliation of graphene from graphite of used Zn–C batteries [20]. The quality of graphene produced by the electrochemical exfoliation can be enhanced by taking mixtures of various electrolytes with pencil rods as electrodes. For the synthesis of graphene sheets, different mixtures of H2SO4 and HNO3 solution were investigated with different volume ratios of H2SO4: HNO3, with maximum oxidation was achieved at 1:1 ratio of both mixtures [21]. In another study, electrochemical exfoliation method was used for the preparation of high-quality water-dispersible graphene using molybdate aqueous solutions as the electrolyte [22]. Further, graphene is very effective against the cancer cells for treatment of cancer patients. Some researchers have demonstrated the cytotoxic effect of graphene with high content of nitrogen on colon cancer cells and antioxidant and protective properties on human endothelial cells [23]. Further, the researchers have investigated the role of Transition Metal Salts During Electrochemical Exfoliation of Graphite for Energy Storage Applications [24]. Recently, colloidal graphene produced by the electrochemical exfoliation of graphite in potassium sulphate and sulfuric acid electrolytes has been successfully utilized for the supercapacitor applications [25, 26]. **Table 2** shows various electro-

*DOI: http://dx.doi.org/10.5772/intechopen.95522*

#### *Recent Progress in the Electrochemical Exfoliation of Colloidal Graphene: A Review DOI: http://dx.doi.org/10.5772/intechopen.95522*

The role of electrolytes is very important in the quality of the graphene produced. The graphene synthesis mechanism in acidic (0.5 M H2SO4), neutral (0.5 M Li2SO4) is compared to non-destructive intercalation in organic electrolyte (1 M NaClO4 in acetonitrile) [19]. Another important advantage of electrochemical exfoliation is that it can be utilized for the synthesis of graphene from electronic waste because it is a great threat to the environment due to difficulty in recycling, difficulty in conversion of waste to useful materials. So, researchers have reported a facile and fast production method of electrochemical exfoliation of graphene from graphite of used Zn–C batteries [20]. The quality of graphene produced by the electrochemical exfoliation can be enhanced by taking mixtures of various electrolytes with pencil rods as electrodes. For the synthesis of graphene sheets, different mixtures of H2SO4 and HNO3 solution were investigated with different volume ratios of H2SO4: HNO3, with maximum oxidation was achieved at 1:1 ratio of both mixtures [21]. In another study, electrochemical exfoliation method was used for the preparation of high-quality water-dispersible graphene using molybdate aqueous solutions as the electrolyte [22]. Further, graphene is very effective against the cancer cells for treatment of cancer patients. Some researchers have demonstrated the cytotoxic effect of graphene with high content of nitrogen on colon cancer cells and antioxidant and protective properties on human endothelial cells [23]. Further, the researchers have investigated the role of Transition Metal Salts During Electrochemical Exfoliation of Graphite for Energy Storage Applications [24]. Recently, colloidal graphene produced by the electrochemical exfoliation of graphite in potassium sulphate and sulfuric acid electrolytes has been successfully utilized for the supercapacitor applications [25, 26]. **Table 2** shows various electrolytes used recently for the electrochemical exfoliation of graphene.


*Colloids - Types, Preparation and Applications*

**5. Recent works on electrochemical exfoliation of graphene**

*Electrochemical exfoliation of graphite for the formation of colloidal graphene.*

Due to the various advantages of the electrochemical exfoliation technique in comparison to others, it has been extensively utilized recently for the preparation of graphene nanosheets for various applications. Recently industrial scale synthesis of few-layer graphene nanosheets have been synthesized where the electrochemical experiment shows that rate of graphene exfoliation increases with the higher concentration of intercalates and accordingly the colloidal conductivity changes [17]. In comparison to graphene, graphene oxide is more environment friendly because of the presence of oxygen-containing functional groups. In Comparison to standard Hummers' method for synthesis of GO, electrochemical exfoliation of graphite is considered facile and green with better crystallinity and higher oxidation degree [18].

*Various steps involved in the formation of colloidal solution of graphene through electrochemical exfoliation* 

**36**

**Figure 3.**

**Figure 2.**

*process.*


**Table 2.**

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