Energy in Nanotechnology: Using Graphene as Electrodes

The present day nanotechnology is using grapheme and other materials as components of the supercapacitors. Indeed, this technology becomes highly prominent in this sector. Using graphene as an electrode proved to be lucrative for some portable and other devices. Nanotechnology is the latest technology of using ultrathin film electrodes, where graphene /MnO2/CNTs are providing efficient results. These materials have higher efficiency in comparison to the conventional materials. In fact, the technology has a great impact over the future devices. The electrodes built by the materials have extended life cycle and small cost. The technology is used for the production of lithium-ion batteries. In this technology, chemically modified grapheme and highly conducting polyaniline (PANi) are used in LBL process.

The novel and superior types of energy technologies are being developed every day. The latest invention of using graphene as electrodes has a great impact on the technical development all over the globe. In this technology, ultrathin film electrodes are used. Such electrodes have good electrical conductivity. Microelectromechanical systems and nanoelectromechanical system devices have higher demand to build up a self-powered system. In fact, nanotechnology is a latest technique of manufacturing conductive, extremely flexible, and strong film supercapacitor electrodes. Such electrodes are based on some nanocomposites like graphene/MnO2/CNTs. The technology is used for the production of lithium-ion batteries. Indeed, such system is regarded as "the fabrication of electrochemical capacitance (EC) electrodes" that stock up energy using nanoscopic charge severance system at the boundary between an electrolyte and electrode. The capacitor built by this technology is highly efficient and has tremendous energy density in comparison to the conventional dielectric capacitors. It increases piezoelectric power generation using a p-type polymer layer. The layer is used on a piezoelectric semiconducting thin film, including possible appliances in some wearable electronics and extra devices. Such technology is highly efficient in the portable devices like mobile phones, laptop computers etc.

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Since the past decades, lithium ion batteries are used intensively in the electrochemical energy transfer and storage devices. Nanotechnology is very important for the future mobile electric devices and hybrid vehicles. It contains high energy density with long cycle lifetime of lithium-ion batteries. The distinctiveness like high reversible capacity, extended cycle life, and small cost made the technology innovative. On the other hand, the technology of layer-by-layer (LBL) self assembly has been used to develop innovative functionalities for a wide range of applications. It is regarded as an important approach towards the production of electrochemical capacitance (EC) electrodes. In this context, chemically modified graphene and highly conducting polyaniline (PANi) are to be enhanced by the LBL process. To reduce the grapheme oxide in the multilayer films, some methods like electrochemical properties of the multilayer film (MF-) electrodes, volumetric capacitance, sheet resistance, and charge /discharge ratio are exploited. According to Sarker and Hong, "graphene is formed from one-atom-thick planar sheets of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice" (12638). The study shows that graphene is an outstanding performer as a candidate for electrode materials in supercapacitors. It has remarkably high thermal conductivity, electrical conductivity, and strength. Furthermore, it covers exceptionally high specific surface area of up to. Chemically modified graphene has good electrical conductivity with large surface areas. These are highly capable applicants for EDLC supercapacitors. Some discoveries prove that polymer/graphene compo-sites, metal oxide/graphene and CNT/graphene can be used as electrodes. PANi andmultiwalled nanotube (MWNT) bilayers composed multilayer film (MF-) electrodes demonstrated superior energy and power densities. These electrodes have long cycle lifetimes in lithium cells. Furthermore, "ultrathin fabrication approaches enable the design novel graphene supercapacitor geometries based on 2D in-plane layouts that achieve high capacitive energy storage characteristics due to large electrochemical surface areas" (Sarker and Hong 12637-38). Agglomeration of graphene nanosheets is prevented by the LBL films composed of graphene/azo polyelectrolyte bilayers. It also enhances the reachable surface area.

Electrochemical Properties of the PANi/RGO Multi-layer Films

The multilayer film (MF) electrodes (S-1, S-2, and S-3) are poised by PANi/RGO bi-layers. The electrochemical executions were assessed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge measurements. According to Bae et al., "cyclic voltammetry from the supercapacitor part shows good electrochemical stability and capacitance of fibre-based electro-chemical capacitors" ( 3448). A platinum wire counter electrode and an Ag /AgCl reference electrode in Na2SO4 electrolyte were comprised by the cell. Using the CV and galvanostatic charge/discharge systems, the prospective of utilizing the MF-electrodes as super-capacitors was evaluated. To determine the exact volumetric capacitance of the MF-electrodes, the CV curves and galvanostatic charge/discharge measurements were utilized. Based on the discharge method, the average volumetric capacitance values, of the MF-electrodes were estimated, in accordance with the following

 

Where I is the current loaded (A),

Δt is the discharge time (s),

ΔE is the potential change during the discharge process (volt), and V is the volume of the active material in a single electrode.

The exceptionally big facet ratio of graphene sheets places restraint on the realistic capacity of graphene-based electrodes at elevated charge/discharge rates.

Synergistic Effects from Graphene and Carbon Nanotubes

The lightweight energy storage systems have been proved to be more flexible. Presently, the system received marvelous importance due to their prospective function in wearable electronics including roll-up displays and other devices, as well. To produce such types of electrodes, desired mechanical and electrochemical properties like highly flexible and robust film supercapacitors are utilized. These electrodes are fabricated based on graphene/MnO2/CNTs nanocomposites. Graphene, CNTs, and MnO2 provide outstanding mechanical properties with synergistic effects. Any of these materials alone cannot provide such effective result. These electrodes provide extremely dynamic material loading (71 wt % MnO2) with areal density (8.80 mg/cm2) and high specific capacitance (372 F/g). It is an excellent rate potential for supercapacitors.

Self-Assembled Hierarchical MoO2/Graphene Nanoarchitectures and Their Application as a High-Performance Anode Material for Lithium-Ion Batteries

Self-assembled hierarchical MoO2/graphene nanoarchitectures have become favorable for the construction in a great amount through a simplistic solution-phase process. For lithium-ion batteries, as an anode material, a-formed MoO2/graphene nanohybrid exhibits highly reversible capacity with excellent cycling performance and good rate capability. Study shows that "the hierarchical rods made rimaryMoO2nanocrystals are uniformly encapsulated within the graphene sheets" (Sun et al. 7100). The synergistic result of the hierarchical nanoarchitecture and the conducting graphene support contribute to the improved electrochemical capability of the hybrid MoO2/graphene electrode. For the superior functional devices, the MoO2/graphene hybrids with a distinct hierarchical topology offer flexible building blocks.

MoS2 Sheet

The strain engineering plays a vital role in the improvement of electronic, photonic, and spintronic performances of tuning band energies of semiconductors. Low-dimensional nanostructures proved to be flexible in this context. It is a challenge to monitor the optical and phonon properties and control strains in atomically thin semiconductors precisely. The developed electromechanical device like biaxial compressive strain to trilayer MoS2 can be applied in this regard. It is covered by atransparent graphene electrode and supported by a piezoelectric substrate. According to Yu Hui et al., "Photoluminescence and Raman characterizations show that the direct band gap can be blue-shifted for ?300 meV per 1%strain" (7126).

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Piezoelectric Nanogenerators

For wireless sensors and microelectronics, it is essential to increase the output power of a nanogenerator as a sustainable power supply. On a piezoelectric semiconducting thin film, applying a p-type polymer layer can highly improve piezoelectric power production. At the film surface, the holes decrease the piezoelectric probable screening consequence that is formed by free electrons in a piezoelectric semiconducting material. In addition, there is a shift in the Fermt level, and transporters from a conducting polymer enhance the power production. According to Lee et al., "the ZnO/P3HT:PCBM-assembled piezoelectric power generator demonstrated 18-foldenhancement in the output voltage and tripled the current, relative to a power generator with ZnO only at a strain of 0.068%". (1969) The output power density crosses 0.88 W/cm3, whereas the average power exchange competence is up to 18%. Such method enables red, green, and blue light-emitting diodes. For the self-powered electronics, this attempt presents an elevated performance with nice piezoelectric energy harvester.

Conclusion

Nanotechnology has achieved a great place in modern science and technology. Multipurpose use of such technology opened a great opportunities in this sector. In this technology, the films used here are ultrathin, composed of positively charged acid doped PANi and negatively charged GO were effectively manufactured on silicon or ITO substrates. To complete it, there LBL self-assembly procedures were utilized. The electrochemical properties of the MF-electrodes depended significantly on both the morphology and the reduction technique used to change GOES to RGO in the multilayer films. The morphologies of the multilayer films were managed by changing the application of either the PANi or the GO. Managing over the GO is one of the most critical tasks. It is determined by the resulting electrochemical properties of the MF-electrode. To measure the thickness of each GO monolayer in the multilayer assemblies, ellipsometry was applied. In S-3, a good agreement with the literature value (?1.3 nm), the thickness was found to be 1.32 nm. The conductivity of a multilayer film built of 15 PANi/RGO bilayers increased from 2.33 (S-1) to 53.35 S/cm (S-3).

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