Researchers at the University of Notre Dame Radiation Laboratory have developed a synthesis method to “drill” holes in reduced graphene oxide using gold nanoparticles as catalysts. This method represents an alternative to the tedious process of drilling one hole at a time with an electron beam or other methods using high temperature without the advantages of post-processing solution chemistry. Graduate student James Radich and Prashant Kamat, the Reverend John A. Zahm Professor of Science in Chemistry and Biochemistry, published their findings, “Making Graphene Holey. Gold-Nanoparticle-Mediated Hydroxl Radical Attack on Reduced Graphene Oxide,” in ACS Nano this month.
Radich was able to generate the Holey Graphene morphology by first depositing gold nanoparticles on the two-dimensional reduced graphene oxide sheets. He then irradiated the suspension with UV light in the presence of hydrogen peroxide, resulting in production of hydroxyl radicals, which are known as strong oxidants. “The interesting part of this work is that you need gold particles,” Kamat said. “Without gold particles, you cannot make holes. The gold essentially catalyzes the oxidation of the carbon-carbon bonds in the graphene sheets to form the holes, and then they move to the next nascent site where new holes are generated.”
Graphene has been widely considered for a variety of applications, including conductive supports for active materials in batteries and fuel cells. Previous studies suggest that graphene sheets with holes promote diffusion of lithium ions in batteries, and the laboratory will conduct further research in that field. Also, creating holes in the graphene sheets creates more edges, which are the predominant sites for graphene’s activity in catalysis. On the other hand, the research raises new questions regarding the stability of graphene materials used in electrode composites where free-radicals are generated.
“It’s really a double-edged study,” Radich said. “We’re able to chemically make in solution a new graphene morphology with many potential applications. On the other side, everyone naturally assumes the chemical stability of graphene when used in these applications. We have shown that, for example, graphene sheets as conductive support for photocatalysts may not be as stable as once thought.”