Draft:Synthesis of graphene from rich husks for supercapacitor application

Graphene is a two dimensional layer of graphite which has a honeycomb hexagonal pattern of carbon atoms, each connected through sp2 bonding. The name "Graphene" merges "graph," referring to graphite, and "ene," indicating carbon-carbon double bonds found in organic compounds. Graphene is typically described as a single-atom-thick layer of sp2-bonded carbon atoms arranged in a hexagonal lattice. This layer is not an intrinsic part of a larger carbon material but is either freely suspended or attached to another substrate.

History

Supercapacitors have proven to be good energy storage devices, and as such the need to improve upon its efficiency. Before the discovery of graphene, precursors used as electrode materials showed great sign of drawbacks given that they were toxic and also required a lengthy processing route. Precursors like graphite required lengthy processing and was heavy electrode materials.

Graphene's discovery brought a huge innovational impact into the game of supercapacitors in that it exhibited some properties such as excellent electrical and thermal conductivity, flexibility, optical transparency, high specific surface area and much more.

Methods For Graphene Synthesis

Various methods of graphene extraction exist some of which includes mechanical exfoliation, chemical method, chemical vapor deposition(CVD) and epitaxial growth. These can further be classified into two main synthesis methods namely Top-down(mechanical exfoliation, chemical method) and bottom-up(chemical vapor deposition(CVD) and epitaxial growth) approach. However, these processes had drawbacks in that they were not scalable for mass production, involved the use of toxic chemicals which were harmful, were expensive to carryout and mostly a discontinuous process.

Two Broad Classification Processes;

In the top-down approach, graphite, a stack of graphene layers held together by weak van der Waals forces, is broken into atomic layers. This is typically achieved through oxidation using strong chemicals like sulfuric acid, sodium nitrate, or potassium permanganate. The oxidized graphite, known as graphene oxide (GO), can then be exfoliated into single to few layers of graphene through rapid heating or thermal shock. However, this method involves toxic chemicals and can alter the graphene structure.

Mechanical exfoliation, another top-down technique, uses external mechanical forces like scotch tape or ultra-sonication to separate graphene layers. While this method has improved, it's not suitable for mass production due to its labor-intensive nature.

In contrast, the bottom-up approach involves growing graphene directly on substrates. Techniques like epitaxial thermal growth on silicon carbide or chemical vapor deposition (CVD) on transition metal substrates allow for large-area, high-quality graphene production. These methods are compatible with current technology but require expensive substrates, high temperatures, and costly gases, limiting their scalability for large-scale production.

Environmentally Friendly Approach

This approach seeks to use a green approach in synthesize graphene this means use of no/less toxics and a more efficient and scalable method.