Modification of Surface Tension of a Green Solvent and Surfactants to Enhance Graphene Synthesis

Graphene is the single layer of graphite, made up entirely of carbon. With many favorable properties, such as high conductivity, incredible tensile strength, flexibility, and a lightweight structure, graphene is one of the first choices in the energy storage industry. The problem with graphene arises in its scalability and producability. Our research finds a process to create high-quality graphene in a cost-effective, scalable, and green manner, for use in supercapacitors. Many papers explore top-down and bottom-up approaches such as redox reactions, flash graphene, epitaxial growth, and chemical vapor deposition (CVD), but they use toxic solvents and costly equipment, both of which are neither good for the environment, nor widely accessible. The most viable solution seemed to be Liquid-Phase Exfoliation, which uses sonication in a solvent to exfoliate the layers of graphite to produce monolayered- or few-layered- graphene. We also tested variability in the time durations of our sonicating machines; the probe sonicator (direct sonication) and the bath sonicator (indirect sonication). By changing the solvent based on its surface tension and surface energy, we tweaked the solvent ratios so that the surface tension of the solvent was similar to the surface tension of graphite, which is 41 mJ/m2. This reduces the potential energy between the two materials and makes it easier to overcome the van der Waals forces. In addition, we experimented with different solvents such as dish soap, hand soap, and an ethanol and water mixture, and different surfactants such as curcumin to observe their effects on yield. We found that the hand soap yield had the most contaminants and was also very dense. The best quality graphene came from ethanol and water, and curcumin and water, with a measured CV capacitance of 13.1 F/g. We used different characterization tools such as FTIR, CV, SEM, and GCD to determine how much graphene we had, and what grade of graphene we had, as well as calculating the specific capacitance and long-term capacitance. In the future, we will test more green solvents and surfactants, and we will attempt with the process of magnetic separation to further exfoliate the graphene. We are also planning on using Raman Spectroscopy in the future to characterize graphene. Finding a simpler, greener, and cost-effective method in which graphene can be synthesized will greatly increase its usage in the electrochemical industry as the cost of manufacturing and its scalability is the main obstacle to the widespread use of graphene.