A team of researchers from the National University of Singapore (NUS) has used graphene to develop a potentially useful technique for producing supercritical water
This was achieved by attaching a layer of graphene on diamond and heating the bonded materials to high temperatures, after which water molecules trapped between them became highly corrosive.
This discovery, led by led by Professor Loh Kian Ping, is claimed to have wide-ranging industrial applications, from environmentally-friendly degradation of organic wastes to laser-assisted etching of semiconductor or dielectric films.
The findings were published online in Nature Communications with Ms Candy Lim Yi Xuan, a Ph.D. candidate at the NUS Graduate School for Integrative Sciences and Engineering as the first author.
While diamond is known to be a material with superlative physical qualities, little is known about how it interfaces with graphene, the one-atom thick substance composed of pure carbon.
A team of scientists from NUS, Bruker Singapore and Hasselt University Wetenschapspark in Belgium, sought to explore what happens when a layer of graphene, behaving like a soft membrane, is attached on diamond. To encourage bonding between the two rather dissimilar carbon forms, the researchers heated them to high temperatures.
At elevated temperatures, the team noted a restructuring of the interface and chemical bonding between graphene and diamond. As graphene is an impermeable material, water trapped between the diamond and graphene cannot escape. At a temperature that is above 400 degree Celsius, the trapped water transforms into a distinct supercritical phase.
‘We show for the first time that graphene can trap water on diamond, and the system behaves like a ‘pressure cooker’ when heated,’ Prof Loh said in a statement. ‘Even more surprising, we found that such superheated water can corrode diamond. This has never been reported.’
Due to its transparent nature, the graphene bubble-on-diamond platform provides a novel way of studying the behaviours of liquids at high pressures and high temperature conditions, which is traditionally difficult.
‘The applications from our experiment are immense. In the industry, supercritical water can be used for the degradation of organic waste in an environmentally friendly manner. Our work is also applicable to the laser-assisted etching of semiconductor or dielectric films, where the graphene membrane can be used to trap liquids,’ said Prof Loh.