Cheap and Sustainable Method of Producing Graphene Discovered

Graphene is a true wonder material. The structure of this super-thin form of carbon is similar to graphite and its geometry resembles that of a honeycomb; at the same time, it is the world’s strongest material. It is used in many fields such as medical science, electrical engineering or materials engineering. However, the current methods of graphene production are expensive, risky and environmentally harmful. The team of Assoc. Prof. Pavel Pazdera from the Department of Chemistry of the Faculty of Science, MUNI, came up with a cheap and environmentally-friendly way of producing graphene.

21 May 2019 Iveta Zieglová

"Monolayer graphene boasts some truly unique mechanical properties, mostly regarding its strength. The material is so light that a 10-litre bag full of graphene would weight only half a kilo. However, its production is so technologically demanding and expensive that it is used mainly in products and technologies with high added value. Otherwise, it simply doesn’t pay off. These are for example semiconductors, microprocessors, batteries and accumulators, aviation industry materials, sorbents, and so on,” explains Mr Pazdera.

Graphene is currently produced using mainly two methods. The first one is a “bottom to top” method typically using copper plates and carbon; it is a very complicated and technologically demanding process. The second method is a “top to bottom” synthesis starting with a several-layers-thick material which is gradually made thinner, ideally to match the height of a single atom of carbon – so-called monolayer. “In this case, so-called intercalation is required – a suitable compound has to be inserted in between the carbon layers. After increasing its temperature the compound turns into a gas which separates the carbon layers by so-called oxidative exfoliation. However, during this process holes may occur in the graphene layer which lowers the quality of the end product,” adds Mr Pazdera while remarking that the process itself is rather risky because of the highly explosive compounds it produces.

Graphene production is also limited by its environmental impact. It generates aqueous waste containing ecotoxic salts of heavy metals such as manganese and chrome. The subsequent disposal of such waste significantly increases the production costs and limits the utilisation of graphene in industrial production.

Waste? Water and salt

The scientists from Masaryk University came up with their own method to prepare graphenoids for a fraction of the cost and without any environmental impact. “Since 2017, we’ve had a patented process which is not entirely eco-friendly because it takes place in acetic acid. However, we’ve managed to improve on it so that the only waste generated by the current method of preparation is water and sodium chloride, or just water. At MU, this invention falls under the category of classified know-how,” says Mr Pazdera. Allegedly, the method is so simple that making it public as a patent application would disclose it. “The only thing I can tell you about it is that it happens in water and we use regular oxidizing agents and catalysts,” he says smilingly.

Simplicity is the thing he’s aiming for in his research. “It has to be cheap and effective, which is what makes it sophisticated. A trivial solution to a non-trivial problem. However, to be able to come up with a simple solution, one has to know the complex problem inside out,” claims Mr Pazdera.

His other inventions adhere to this principle as well. For instance a flow reactor with a microwave source and a catalytic bed on which he and his team have worked for the last three years – also thanks to the Proof of Concept financial support from the TA CR Gamma Project. What looks like a strangely modified microwave oven is, in fact, a functional prototype of a device which is capable of speeding up chemical reactions which normally take 24 hours to just tens of minutes using a suitable, cheap, immobilized catalyst. “We’re using an environmentally friendly method and we save energy because we only need one-tenth of the output of a regular household microwave, which is just tens of Watts. We use a synergy of several different methods which we combine in our flow reactor,” he explains. This invention also has a chance of taking hold in both the industry and laboratories. The international audit firm PricewaterhouseCoopers appraised this complex solution at more than USD 20 million. Negotiations are already being conducted regarding the licensing of the device e.g. with the Entwick Company.

Companies are interested in green chemistry

There is a common thread of so-called “green” or “sustainable” processes running through Pavel Pazdera’s research. And Companies are interested not only because of the environmental aspect. “Their main goal is profit. Any company’s decision to switch to environmentally friendly processes is mostly tied to reducing costs – for instance those of dangerous waste disposal or other hazards,” says Mr Pazdera pragmatically.

His “green” graphenoids caught the interest of Senergos who have co-funded their development. The scientific team is now looking for an investor to further fund the project. “We have designed a fully automatic production line which needs to be constructed and tested. We’re looking for ways of putting our technology into practice; it could be used for instance in material properties or sorption and desorption processes. As for materials and other application testing, so far we’ve been limited by the lack of funding. We’re successfully testing sorption processes with the Universidad de La Laguna, Tenerife, where we tried removing residual drugs from wastewater and managed to do so very effectively; we achieved very low concentrations otherwise unattainable for example by active charcoal,” says Mr Pazdera.

The researchers are tackling yet another problem. “The leaves of graphene have better mechanical properties when they’re not distributed randomly in the material but face the same direction. That’s why we’re currently looking for a method to change their orientation. If we manage to solve this problem, it will be an extremely significant discovery because it will give us a relatively cheap product. The owner of the know-how will also have the market advantage and strong demand can be expected,” concludes Mr Pazdera.

Dry graphene product and water dispersion thereof

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