RESEARCHERS have developed a method to turn graphene oxide into a mouldable dough, making it safer to transport and easier to work with.
The dough can be easily shaped and reshaped into free-standing structures. It can also be diluted to create gels or dispersions, or dried to create dense solids which are electrically conductive and chemically stable, this completing the graphene oxide (GO)-water “continuum”.
Previous work on making free-standing forms of graphene oxide was limited to making thin films or foams. A major challenge was that water added to the graphene oxide was absorbed locally, resulting in non-uniform hydration. Now researchers at Northwestern University, US, have created a mouldable form of GO by using aerosolised water mists to uniformly hydrate the GO.
“The dough state of graphene oxide has very high GO loading (eg 50 wt%), which means that you can only add very small amount of water to solid GO,” said Jiaxing Huang, Professor of Materials Science and Engineering at Northwestern's McCormick School of Engineering, who led the study. “The challenge is to uniformly hydrate a solid GO material (typically in the form of a film, foam or powders) with such little amount of water.”
The research team added a high concentration of GO to water instead of using binding additives which would have needed further processing to remove them. "Adding binders such as plastics could turn anything into a dough state," said Huang. "But these additives often significantly alter the material's properties."
The new form of the material also solves a storage and transport problem for GO. "Currently graphene oxide is stored as dry solids or powders, which are prone to combustion, or they have to be turned into dilute dispersions, which multiply the material's mass by hundreds or thousands," said Huang. He described how his most recent GO delivery of 5 kg was dispersed in 500 L of liquid. "It had to be delivered in a truck. The same amount of graphene oxide in dough form would weigh about 10 kg, and I could carry it myself."
Graphene oxide is often used to make graphene, which is a single atom sheet of carbon that is both lightweight and strong and has numerous potential applications. Producing graphene at scale has many challenges, and using GO to produce graphene is still limited to batch processes. “I don't think [GO dough] will significantly change the ‘GO to graphene’ chemistry (which still needs quite some work),” said Huang. “[However] since it is a lot easier to process GO than graphene, we think the GO dough is a nice precursor to make solid graphene structures. This is like shaping a bread dough before baking it since the baked bread can no longer be easily shaped.”
Omar Matar, Professor of Fluid Mechanics at the Department of Chemical Engineering at Imperial College London, who was not involved with the work, commented: “It is good to see work around the manufacturing of graphene oxide-based products, and even better to see how this could be extended to graphene-based products. This is a potentially efficient way to store and handle graphene oxide and reduced graphene oxide.”
The method of hydrating graphene oxide with aerosolised water mists is scalable, and Huang said that while he doesn’t make GO at commercial scale in the lab, he would love to work with manufacturers to customise their products into dough state. "My dream is to turn graphene-based sheets into a widely accessible, readily usable engineering material, just like plastic, glass and steel. I hope GO dough can help inspire new uses of graphene-based materials.”
Nature Communications http://doi.org/c2jb
Catch up on the latest news, views and jobs from The Chemical Engineer. Below are the four latest issues. View a wider selection of the archive from within the Magazine section of this site.