PRODUCTION OF REDUCED GRAPHENE OXIDE BY HYDROHALIC ACIDS Samuel Cooke, James Murray Graphene is a material consisting of a 2- dimensional hexagonal lattice of carbon atoms, and has many unique properties such as a very high conductivity and tensile strength. Pure graphene is very difficult to produce on a large scale, so a proposed solution to this problem is to reduce graphene oxide (rGO). Graphene oxide (GO), shown on the left, is an impure form of graphene as it contains epoxy and hydroxyl groups. By removing these impurities, one can create rGO with properties similar to pure graphene. There are many methods of reducing graphene oxide; however, the method which has proven to be the most scalable and efficient is the use of hydrohalic acids, such as HI, as a reducing agent. With the use of a 55% HI solution, rGO with a conductivity of 298 S/cm (Siemens per centimeter) has been produced, which is much greater than most other methods of reduction. A C/O (carbon to oxygen) ratio greater than 14.9 has been achieved, indicating that there are less impurities and that the material works as a better substitute for pure graphene than rGO produced with other methods. The figure shows the HI reacting with different impurities to reduce GO. Water Filtration By creating nanopores of a certain size, water is able to pass through the membrane without allowing other pollutants such as salt to permeate. This process is shown in the figure at the right, where the green bubbles represent pollutants. This could provide a solution to the growing problem of water shortages around the world. Energy Storage Ultra-capacitors created with rGO could be implemented into buses, with savings of up to $200,000 in gas during the bus’s lifetime. Energy generated from power plants is often wasted when not used, but the use of ultra-capacitors in tandem with other technologies could store this wasted energy for later use. The United States currently has only capacity for storage of 3% of possible output. One must take into account the impacts that this process may have on the environment if performed on a large scale. The production of graphene oxide requires graphite, which mainly is mainly derived from large mining operations. The use of rGO in ultra-capacitors would reduce the need for batteries which are mainly produced from rare earth elements derived from Chinese mines. This makes the use of rGO important for economic sustainability as well. Implementation of rGO for water desalination could allow for more sustainable development in nations without access to clean water. Conductivities As shown in this figure, the use of HI as a reducing agent yields a very high conductivity and C/O ratio. The reason that the use of HI is examined instead of HI/AcOH is because of the amount of research done examining HI compared to HI/AcOH is greater. Reducing AgentConductivity (S/m)C/O Ratio Well Defined Mechanisms HI/AcOH HI NH 3 BH 3 -Ammonia Borane C 14 H 14 O 2 P 2 S 4 -Lawesson's4760 Thiourea dioxide/NaOH Thiourea dioxide/Ammonia2906 NaBH 4 -Sodium Borohydride824.8 HBr Proposed Mechanisms Zn/HCL NaHSO 3 -Sodium Bisulfate C 6 H 8 N 2 -Phenylhyrazine C 7 H 8 O-Benzyl Alcohol N 2 H 4 -Hydrazine Chemical Reduction Ultra-capacitors The implementation of graphene-based ultra- capacitors could cut back on the amount of fossil fuels burned by buses, allowing renewable energy to be used in place of non-renewable forms of fuel.