Graphene powders are now routinely manufactured at sizes of hundreds of tons, with annual production expected to reach almost 3800 tons by 2026. Here, AZoNano sheds light on the sources of the highest quality of graphene.
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The Global Graphene Market is estimated to exceed $700 million (USD) by 2030 due to increased demand for durable, lightweight and efficient materials in energy storage, composites and electronics applications.
As a result, there has been an increased motivation for the development of high-output and inexpensive production methods for high-quality graphene and materials within the graphene family.
Graphite
Graphite is a layered material in which each carbon atom is surrounded by three others forming a hexagonal structure. Extremely strong carbon bonds, which are even stronger than those in diamond, are present between these atoms in each layer.
Despite this, the bonds between layers are weak. Graphene is made up of a single layer (monolayer) of carbon atoms in a graphite structure that is tightly held together in a honeycomb-like hexagonal lattice. Since graphite is composed of many loosely stacked graphene sheets, the adhesive force is enough to peel off a few graphene layers.
Liquid exfoliation and electrochemical exfoliation are more commercially viable ways to make graphene of high quality. With a market capitalization of $428 million (USD) in 2022, the Canadian firm NanoXplore dominated the global market for powder graphene-producing companies. Companies such as Graphenea, Applied Graphene Materials, Directa Plus, First Graphene Limited, and NeoGraf are the top suppliers of graphene flakes derived from graphite.
Carbon Rich Gases
It has been reported that carbon-containing gases like methane, acetylene, and even carbon dioxide can be used to produce graphene sheets on a metal substrate. During this process, gas species are introduced into the reactor and travel through a heated zone.
At the surface of the metal substrate, hydrocarbon precursors are broken down into carbon radicals, which leads to the formation of single-layer or multi-layer graphene.
The technique is referred to as chemical vapor deposition (CVD), though note that the graphene produced by CVD is a transparent sheet of carbon atoms and not a flake.
General Graphene Corporation and Grolltex in the United States, Charmgraphene and Graphene Square in South Korea, Graphenea in Spain, Wuxi Graphene Films Ltd and 2D Carbon Tech in China, and Paragraf in the United Kingdom are all making high-quality sheet graphene on a large scale. Levidian, based in the United Kingdom, has created a LOOP reactor that produces high-grade pristine graphene flakes by decarbonizing the greenhouse gas methane.
Silicon Carbide
Another method for producing large-scale epitaxial graphene is the thermal decomposition of epitaxial graphene on silicon carbide (SiC). When SiC is heated to 1650 degrees Celsius at standard atmospheric pressure for a short time, anywhere between one and twenty minutes, the Si atoms desorb, leaving behind the carbon atoms, which subsequently rearrange themselves into graphene layers.
Thermal SiC decomposition removes the necessity for graphene transfer in electronic device, making it compatible with CMOS technology. Graphensic is a global leader in producing high-quality epitaxial graphene on silicon carbide.
Natural Sources
Biomass is a great alternative starting material for making valuable carbonaceous materials because it is cheap, eco-friendly, and can be made in large quantities in a sustainable way. Pyrolysis of honey, sugarcane extract, animal waste, essential oil, rice husk, vegetable waste, leaf waste, coconut shell, orange peel, and other raw materials and waste products has been said to be a low-cost, environmentally friendly way to make graphene.
For example, GrapheneCR and Bio Graphene Solutions (BGS) are sustainable manufacturers and distributors of graphene that produce high-quality graphene using biochar from wood waste rather than graphite.
Graphene from Municipal Waste
Recently, a new method for producing graphene has been developed. Here, the process converts carbon-rich household waste, such as used tires, plastic water bottles, and food containers, as well as naturally occurring carbon sources, like petroleum coke, coal, and biochar, into graphene.
Any carbon-rich material is treated with a high voltage and high current pulse for very short time of a hundred milliseconds in this technique, and fresh turbostratic graphene is produced. Flash Joule Heating (FJH) was invented by Prof. James Tour at Rice University and is now being commercialized by Universal Matter.
Miscellaneous Sources of Graphene Production
Since carbon is the sole component of graphene and is the fourth most plentiful element in the universe by mass, it is anticipated that any natural or artificial material with a high carbon content will be able to produce graphene. In fact, carbon makes up 18% of the human body.
Graphene and its derivatives are obtained from a variety of diverse, even exotic sources, such as cookies, toast, and even wood, using a process known as laser-induced graphene. Graphene can also be synthesized from waste plant leaves by thermal decomposition at high temperatures in an inert atmosphere, a process known as pyrolysis.
Concluding Remarks
The growing demand for low-cost, high-output, and high-quality graphene production technologies is directly proportional to the expansion of the graphene market. The conventional production techniques, which involve using graphite or a carbon-rich gas, have been pretty successfully commercialized.
On the other hand, alternative production processes are still in the early phases of development but can potentially transform a number of low-cost and environmentally acceptable carbon sources into high-quality graphene.
References and Further Reading
Hernandez, Yenny, et al. (2008). High-yield production of graphene by liquid-phase exfoliation of graphite. Nature nanotechnology. https://www.nature.com/articles/nnano.2008.215
Deng, Bing, et al. (2019). Toward mass production of CVD graphene films. Advanced Materials. doi/full/10.1002/adma.201800996
Mishra, Neeraj, et al. (2016). Graphene growth on silicon carbide: A review. physica status solidi. doi/full/10.1002/pssa.201600091
Al-Ahmed, A., et al. (2022). Graphene from Natural Sources: Synthesis, Characterization, and Applications (1st ed.). CRC Press. doi.org/10.1201/9781003169741
Karidis, A. (2020). Can Graphene from Waste Be a Breakthrough for Some Manufacturers? [Online] Waste 360. Available at: https://www.waste360.com/recycling/can-graphene-waste-be-breakthrough-some-manufacturers
Need graphene? Grab a saw (2017). Availabe at: https://news2.rice.edu/2017/07/31/need-graphene-grab-a-saw-2/
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