Synthetic Routes to Graphene for Applications in Barrier Materials and Energy Storage
- Author(s): Dubin, Sergey
- Advisor(s): Kaner, Richard B
- et al.
New techniques for rapid graphite oxide reduction are illustrated. By exposing graphite oxide to a high intensity light, such as a camera flash, rapid deflagration and deoxygenation takes place. The resulting graphitic material is a conductor, with two orders of magnitude higher surface area than its insulating precursor. The technique has potential applications in micro patterning as well as distributed ignition. Flashed graphite oxide is also dispersable in a variety of organic solvents, making it compatible with polymer processing. Another synthetic route to graphene is through solvothermal reduction of graphite oxide. Refluxing dispersions of graphite oxide in N-Methyl-2-pyrrolidone yields charge stabilized colloidal dispersions of graphene. The mechanism of reduction is thermal in nature, while charge stabilization is accomplished through functionalization of graphene NMP moieties and surface energy matching of NMP to graphene sheets.
Conductometric graphene/Pd(0) hydrogen sensors with increased sensitivity compared to pure graphene is demonstrated. Pd(0) nanoparticles on graphene's surface lower the adsorption energy barrier for H2 molecules and improve the surface chemisorption of H2.
An inexpensive, solid-state method for producing graphene based electronic materials is presented. Utilizing an inexpensive LightScribe DVD drive to reduce graphene oxide to graphene, patterning any design on a variety of substrates is demonstrated. Highly reduced laser scribed graphene shows promise in applications such as supercapacitors, sensors and electrocatalysts. Metal nanoparticles can be grown directly on the graphene surfaces using metal salt precursors. Light initiated reactions enable formation of nanoparticles within seconds of laser exposure. Such a universal approach to nanoparticle formation is suitable for applications from supercapacitors to catalysis.
An investigation into barrier properties of graphene and graphene oxide films illustrate excellent barrier characteristics of graphene oxide to all gases at STP conditions with rates of permeability being directly related to the kinetic diameter of the gas. Due to the hydrophilic nature of graphene oxide, it is highly susceptible to permeation of water through its layered structure. Barrier properties of graphene to water illustrate at least 60 times lower rates of permeability per unit of thickness.