Oily alchemy: Turning soybeans into graphene
Graphene, a thin film of crystalline carbon generally just one atom thick, is being slated as the new wonder material and shows high promise for application in a range of diverse technologies, including energy storage, water purification systems, ultrasensitive detectors, and medical devices. But it has always had a catch: It is expensive to produce. Now researchers at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia have developed a method to produce graphene quickly and cheaply from the humble soy bean, and without the need for exotic gases or complex production techniques.
Using their bespoke "GraphAir" technology that removes the need for potentially explosive compressed gases such as methane and hydrogen, CSIRO researchers have grown graphene film using a natural precursor (soybean oil) that does not require any vacuum processing or many hours in a high temperature kiln, both of which are required in the standard chemical vapor deposition (CVD) techniques currently used to create graphene.
"This ambient-air process for graphene fabrication is fast, simple, safe, potentially scalable, and integration-friendly," said CSIRO scientist Dr Zhao Jun Han. "Our unique technology is expected to reduce the cost of graphene production and improve the uptake in new applications."
To grow their graphene, CSIRO's GraphAir uses a catalyst of relatively inexpensive polycrystalline nickel (Ni) sheets. Graphene production takes in a sealed quartz tube, where heating the soybean oil to around 800 °C (1470 °F) for approximately 26 minutes breaks it down into the various carbon elements that are essential for the synthesis of graphene. The temperature is then maintained for a further three minutes to ensure proper dissolution of the carbon atoms through the Ni substrate.
By restricting air flow into the quartz tube, the produced carbon does not further transform into carbon dioxide or other gases and, by strictly maintaining the applied temperature and the cooling rate, the process produces good quality graphene film.
"Our GraphAir technology results in good and transformable graphene properties, comparable to graphene made by conventional methods," said CSIRO scientist Dr Dong Han Seo.
Whilst other graphene production methods aimed to reduce costs, such as The University of Glasgow's process using thin copper sheets, most still seem to be centered around CVD methods of deposition and standard chemical precursors. CSIRO's new method, however, can use almost any other type of organic oil, even waste oil from frying or barbecuing, and transform it into graphene film.
"We can now recycle waste oils that would have otherwise been discarded and transform them into something useful," said Dr Seo.
With some way to go before the new process is ready for commercial release, the CSIRO is currently on the lookout for industry partners to come up with unique ways to employ their graphene.
The results of this research were recently published in the journal Nature.