Making "green" graphene from gum trees could cut production costs by 200 times
The wonderful potential of graphene has been well covered on our pages, with its supreme strength, ultra-thin profile, and excellent electrical and thermal conductivity opening up all kinds of possibilities. One thing missing from all of this is a cost-effective way to produce it, but a team of researchers now believe they may have discovered a key to this hiding in the bark of Australian eucalyptus trees.
One of the more promising means of producing graphene sheets on a meaningful scale involves the chemical reduction of graphene oxide, which is graphite treated to separate into single or a few layers. But the agents used for this chemical reduction are often toxic, presenting a threat to people and the environment, which led scientists at RMIT University's Centre for Advanced Materials to look for more agreeable alternatives.
"Generally, eucalyptus leaves are packed with oil glands that produce the aromatic compounds that give us their distinctive scent," lead researcher Suresh Bhargava explains to New Atlas. "These compounds help protect the tree from attack by pests. Thus, we have thought of using these aromatic compounds in bark extracts as a reducing agent for the synthesis of graphene."
Key to this greener method of chemical reduction, Bhargava says, is a cocktail of 29 polyphenolic compounds, including catechin, which is abundant in dark chocolate and green tea, gallic acid and caffeic acid, which can be found in red wine. Together in an aqueous solution, these compounds worked together to produce the desired chemical reaction, leaving the team with a "green" form of graphene that was safer, cheaper and more sustainable to produce.
"Eucalyptus bark extract has never been used to synthesize graphene sheets before and we are thrilled to find that it not only works, it's in fact a superior method, both in terms of safety and overall cost," says Bhargava. "Our approach could bring down the cost of making graphene from around $US100 per gram to just 50 cents, increasing its availability to industries globally and enabling the development of an array of vital new technologies."
The team tested its green graphene as a supercapacitor and found that it performed just as well as graphene produced through traditional means. From here, the researchers will work to fine tune their approach to make it more efficient, and then work towards commercial applications.
"In our green chemistry approach, we have used eucalyptus bark extract, which has around 29 polyphenolic compounds that are responsible for the reduction of graphene," Bhargava tells us. "Our next step is to find out the selective reduction of graphene oxide from these 29 polyphenolic compounds. If we find the selectivity, then the separation of these compounds and further producing graphene in a cleaner way can be improved. Once if we get the efficiency in high, we will try to make our lab scale synthesis to pilot scale, then next to industries."
The research was published in the journal Sustainable Chemistry and Engineering.