**3.2 Energy applications of nanocarbon-polymer-based composites**

Economy of any country is directly boom if they can produce and store energy particularly from renewable resource. In this viewpoint carbon-based nanomaterials and their composites can play an important role in the area of energy harvesting and energy storage. It is well known most of the nanocarbon composed of sp2 hybridization and possessed excellent properties such as, high pore size distribution, high surface area, with enhanced mechanical properties and improved electrical properties. In recent years, nanocarbon and nanocomposites are widely applied for developing energy storage and energy saving devices/instrument. Photovoltaic cells are commonly known as solar cell used as an alternative device for harvest renewable energy sources. Photovoltaic cells can be classified in two categories such as, thin films and crystalline silicon photovoltaic cells. Earlier, silicon, cadmium, copper-based compounds are used in the semiconductors used [81, 82] applied in energy storage devices. Nowadays thin-film group photovoltaic cells used platinumbased semiconductor for high band width/specific related applications. But, high cost and availability of platinum increases overall cost of an instrument. In this case carbon-based nanomaterials/composites can play an alternative role of platinumbased materials due to its superior properties [83]. Generally, nanomaterials prepared from graphene are used to enhance electron carriage and boost the efficiency of solar energy conversion [84]. Graphene-based materials can also be used in fuel cells and batteries due to its favorable properties.

Supercapacitors are used for energy storage devices applied in electric vehicles, hybrid electric vehicles, backup power cells, and portable electronic devices due to its advanced properties such as, high-power density, very short charging time, and high cycling stability. The main mechanism of storage of energy in super capacitors are pseudo capacitance and electrochemical double-layer capacitance. In pseudo capacitor, faradic reactions mechanism is responsible for charge transfer processes.

*Green Chemistry Applications*

electrical and mechanical properties [7].

process, carboxylic groups (–COOH) is attached with CNT surfaces. Oxidation of CNT is very important and creates oxygen carrying groups (–COOH and –OH), which makes CNT feasible for further functionalization without affecting their

The outstanding physiochemical properties of nanocarbons have triggered interest, toward the applicability of nanocarbons, in multiple area including adsorption, photocatalyst, fertilizer, nanobiotechnology products, environmental materials, and renewable energy related application etc. De Volder et al. reported industrial scale production approximately up to several thousand tons of nanocarbon [17]. Properties like, high thermal stability and mechanical strength of nanocarbon make them suitable alternatively as fillers provides high aspect ratio for nanocomposites materials. Therefore, the prepared nanocomposites materials exhibited enhanced mechanical and other properties as compare to their starting primitive materials [53]. Nasibulin et al. reported the composite material based on cement matrix in which the addition of nanocarbon to original materials exhibited higher strength composite material [54]. Use of low weight, high strength materials in mechanical equipment improves the overall efficiency with low energy consumption. Regarding this use of nanocarbon based materials in energy generating machine such as, turbine as a lightweight and mechanically tough material is desirable [55, 56], and non-corrosive nature and insoluble nature of sp2 hybridized nanocarbon as fillers for marine turbines [57], various electronic applications [58], automotive industry [59], aviation [60], sport equipment allow to use strong and light weighted materials, which generates economical energy generation at optimal energy consumption. Fullerenes and composite based materials are frequently used in pharmaceutical industries [61]. Nowadays, graphene and its composite are frequently in high demands in various applications such as, electronics, solar cell, biochemical sensors [62]. Carbon based nanomaterials based composite materials having excellent properties like high tensile strength, flexibility and good electrical conductivity that make them more favorable for electronics applications [63]. Similarly, the graphene-carbon nanotube/polyvinyl alcohol based composite show high rigidity, strength, and ductility in comparison with conventional nanocarbon materials. Although there is a dramatically increase in the resistivity witnessed for graphene-carbon nanotube/polyvinyl alcohol-based composite, Therefore, such composite materials can be a suitable as a smart stretchable insulator devices using formed by combining the property of conductive nanocarbon materials with epoxy

**3.1 Environmental applications of nanocarbon-polymer-based composites**

Ecological balance is essential which is majorly affected by different pollutants. Therefore, it is difficult to check ecology balance simultaneously with the rapid growth of industrialization and civilization. In this regard, it is required to increase effectiveness by taking some corrective measures in pre-existing methods of controlling pollutions [65, 66]. In light of nanotechnology knowledge, advanced nanomaterial/composite materials can be developed that significantly enhanced the performance of different pre-existing treatment technologies [55, 57]. For example nanocarbon provide high specific surface area thus, carbon-based nanomaterial/ composites provide high specific surface for the adsorption process [29, 30] oxidation process [67, 68], and electrochemical applications [69, 70]. Although, the

**3. Potential applications of carbon-based nanomaterials**

**6**

polymer [64].


**9**

**SN**

6

Graphite

Heating, drying, filtration, mixing

K2S O2 8, P

H

O2 2

O2

5, H2SO4, KMnO4,

Heating: 80°C,

ice bath: 20–35°C,

mixing: 35°C for 2 h

Mixing: 50-0 °C for

To prepare higher

[94]

thermal energy

storage material

12 h, Drying: 50°C,

sonicated; 1 h

powder

7

Graphene

Heating, drying, filtration, mixing

Polyethylene glycol, H

KMnO4, H2SO4, HCl, H

O2 2

 PO3 4,

oxide,

graphene

nanoplatelets

8

Single wall

Absorption, drying, Nitration

HNO3, Ag/AgCl electrode,

Nitration: 10 h,

Application in

[95]

biofuel.

methylene blue

doping: 3 h

Heating: 60°C,

To prepare enhanced

[96]

thermal conductive

material

Supercapacitor for

[97]

energy storage

ultrasonicated at

pulse velocity of

25 m/s for 20 min

methylene blue

carbon

nanotube

9

carbon

Melting/heating, sonicated

graphite nanoplatelets, phase

change materials

nanotubes

10

Porous carbon

Oxidation, absorption

Sulfuric acid

and hydrous

RuO2

*Application of nanocarbon based materials in energy and environmental field.*

**Table 1.**

Energy Application

**Nanomaterials**

**Method**

**Materials used**

**Conditions**

**Application** Fabricating of various

[93]

microelectrical

devices

**Ref**

*Recent Developments in Nanocarbon-Polymer Composites for Environmental and Energy…*

*DOI: http://dx.doi.org/10.5772/intechopen.85626*


*Recent Developments in Nanocarbon-Polymer Composites for Environmental and Energy… DOI: http://dx.doi.org/10.5772/intechopen.85626*

> **Table 1.** *Application of nanocarbon based materials in energy and environmental field.*

*Green Chemistry Applications*

**8**

**SN**

Environmental

1

Multiwall

Oxidation, filtration, drying

carbon

nanotube

2

Oxidized

EDA, N - HATU, filtration, drying

NH2 materials

Sonicated; 4 h; 40°C

Heavy metal removals

[68]

(Cadmium and lead

reduction)

multiwall

carbon

nanotube

3

Multiwall

Oxidation/reduction/pyrolysis

Ethanol/ferrocene/thiophene

Airflow, 400°C, argon

ciprofloxacin

[90]

reduction from

aqueous solution

Wastewater treatment

[91]

flow, 600–900°C

carbon

nanotube

4 5

Graphite Oxide

Oxidation, sonicated; washed; dried

Na2S O2 3

Graphitic oxide

Oxidation, filtered; washed; dispersed

NaNO3, H2SO4, KMnO4, H

O2 2

Vigorous agitation

20–66°C, dilution:

98°C, 15 min

Sonicated; 1 h,

Heavy metal removal

[92]

(mercury Hg2+

reduction)

disproportionation;

30 min

Application

**Nanomaterials**

**Method**

**Materials used** H2SO4: HNO3 (3:1)

**Conditions** Sonicated; 3 h; 40°C

Heavy metal removal

[67]

(Cadmium reduction)

**Application**

**Ref**

Many metals/oxides/conducting polymers are good examples of the pseudo capacitance process. While, in electrochemical double-layer capacitance processes, charges are accumulated at the interface by the mechanism of adsorption/desorption process of electrolyte ions on a large surface area electrode materials. So, in this regards carbon-based nanomaterials can play an important role in the supercapacitor preparations [85]. Supercapacitors based on nanocarbon have many advantages over conventional (metal-based) supercapacitor, such as, high cycling stability, high power density and low energy density limits for their applications in batteries [86].

Excellent mechanical and electrical properties of nan0carbon-based materials (carbon nanotube) offer an exposed surface to functionalize and make them suitable for energy storage. But, it has some disadvantages such as, moderate capacitance due to low density of nanomaterials [87]. The lithium-ion battery is alternative type of energy storing substance, which holds energy as a chemical energy. It has many advantages over capacitors such as, high power density, and less greenhouse gas emissions possibilities [88]. Nanocarbon materials/composites are used in the lithium batteries because structure of the nanocarbon-based material usually express some common factors such as, the amount of lithium that is reversibly incorporated into the carbon lattice, the faradic losses during the first charge– discharge cycle, and the voltage profile during charging and discharging.

Carbon based nanomaterials such as, carbon nanotubes, activated carbons, and graphene based nanosheets are suitable for sustainable energy storage devices, because, carbon materials have many favorable properties such as, light weight, low cost, easy processability, adaptable porosity, and simplicity of chemical modification [89]. Generally, higher specific surface area and pore size distribution of nanocarbon structures allow them to increase the performance of electrochemical capacitance in terms of both the power delivery rate and the energy storage capacity. Some nanocarbon based materials used in the environmental and energy application are shown in **Table 1**.
