The new process doesn’t require any additional steps or chemicals to produce graphene in its pristine form. “The innovation and technology behind our material is our ability to use a thermodynamically driven approach to un-stack graphite into its constituent graphene sheets, and then arrange those sheets into a continuous, electrically conductive, three-dimensional structure” says the lead scientist in the study. “The simplicity of our approach is in stark contrast to current techniques used to exfoliate graphite that rely on aggressive oxidation or high-energy mixing or sonication – the application of sound energy to separate particles – for extended periods of time. As straightforward as our process is, no one else had reported it. We proved it works”.
A distinctive feature of graphene that seems like an obstacle to many – its insolubility – stands at the heart of this study. Since it doesn’t dissolve in liquids, the team place graphite at the interface of water and oil, where the graphene sheets spontaneously spread to cover the interface and lower the energy of the system. The graphene sheets are trapped at the interface as individual, overlapping sheets, and can subsequently be locked in place using a cross-linked polymer or plastic.
While graphene composite materials have many potential uses in various fields, the team chose to apply this technology to improving standard methods for the desalination of brackish water. With SPARK funding, the team is developing a device that uses graphene nanocomposite materials to remove salt from water through a process called capacitive deionization, or CDI.
CDI relies on inexpensive, high surface area, porous electrodes to remove salt from water. There are two cycles in the CDI process: an adsorption phase where the dissolved salt is removed from the water, and a desorption phase where the adsorbed salts are released from the electrodes by either halting or reversing the charge on the electrodes.