Polycrystalline 2D Nanomaterials
The new era of technology is leading us towards unconventional, clean energy as well as more compact, smaller and durable devices. Fossil fuels were the major source of energy for the last few centuries, but it was not a renewable source of energy. A series of environmental issues have been emerging since the last century as a result of the very high consumption of fossil fuels. Supercapacitors are the latest energy storage devices also called ultra-capacitors or electrochemical capacitors, which are designed to bridge the gap between batteries and capacitors to form fast charging energy storage devices to support intermediate. Storage of these supercapacitors is directly affected by the nanomaterials used for the electrode. So there is direct connection between Nanomaterials and the quality of capacitors.
The field of research in two-dimensional (2D) materials has been enjoying spectacular growth during the past decade. This activity was triggered by pioneering works on graphene, a 2D semi-metallic allotrope of carbon that has outstanding properties. Furthermore, other atomically thin monolayer systems, which possess some very valuable properties for many applications, have soon joined the field thus extending the palette of available 2D materials. Examples are insulating monolayer hexagonal boron nitride (h-BN) and semiconducting transition metal dichalcogenides (TMDCs) MX2 (M = Mo, W; X = S, Se) characterized by electronic band gaps between 1.1 eV and 1.9 eV. The diversity of 2D materials further opens the possibility for such atomically thin crystals to be combined in complex hetero-structures by stacking them on top of each other, thus giving rise to a whole new paradigm of nanoscale engineering.
Graphene, ‘‘the mother of all graphitic forms of carbon”, is a single layer of carbon atoms that are held together by a backbone of overlapping sp2 hybrids bonds. Due to its two dimensional (2D) honeycomb space frame structure (illustrated in Figure 1), Graphene has outstanding physical and mechanical properties. The unique properties of the graphene sheet are tabulated in Table 1.
|Bond length (Å)||1.42|
|Young’s modulus (TPa)||~1|
|Tensile strength (GPa)||~100|
|Shear modulus (GPa)||280|
|Thermal conductivity (W m-1 K-1)||~5000|
|Thermal stability (oC)||500-600|
|Band gap (eV)||0|
|Specific surface area (m2 g-1)||2630|
Due to its exceptional properties, it has attracted increasing research effort for developing new engineering applications such as nano-actuators, nano-sensors, gigahertz oscillators, drug deliverer, field effect transistors (FET), memory devices, sensors, transparent conductive films, clean energy devices, graphene field emission (FE), graphene-based gas and biosensors, transparent electrodes, battery, supercapacitors, electrical double layer capacitors (EDLCs), pseudocapacitors, graphene anodes, solar cells, energy production and storage, optoelectronic applications and room temperature humidity sensing applications. Researchers are also exploring the tribological properties of graphene. In addition to these nanotechnologies, graphene is also listed among the top potential nanofillers for developing nanocomposites with improved mechanical properties and thermal and electrical conductivities.
Image Reference:- https://mewburn.com/graphene-a-whole-new-2d-world/