Ruoff and his team prepared chemically modified graphene material and, using several types of common electrolytes, have constructed and electrically tested graphene-based ultracapacitor cells. The amount of electrical charge stored per weight (called “specific capacitance”) of the graphene material has already rivaled the values available in existing ultracapacitors, and modeling suggests the possibility of doubling the capacity.
“Our interest derives from the exceptional properties of these atom-thick and electrically conductive graphene sheets, because in principle all of the surface of this new carbon material can be in contact with the electrolyte,” says Ruoff, who holds the Cockrell Family Regents Chair in Engineering #7. “Graphene’s surface area of 2630 square meters per gram (almost the area of a football field in about 1/500th of a pound of material) means that a greater number of positive or negative ions in the electrolyte can form a layer on the graphene sheets resulting in exceptional levels of stored charge.”
The U.S. Department of Energy has said that an improved method for storage of electrical energy is one of the main challenges preventing the substantial installation of renewable energies such as wind and solar power. Storage is vital for times when the wind doesn’t blow or the sun doesn’t shine. During those times, the stored electrical energy can be delivered through the electrical grid as needed.
Ruoff’s team includes graduate student Meryl Stoller and post-doctoral fellows Sungjin Park, Yanwu Zhu, and Jinho An, all from the Mechanical Engineering Department and the Texas Materials Institute at the university. Their findings will be published in the Oct. 8 edition of Nano Letters. The article was posted on the journal’s Web site this week.
This technology, Stoller says, has the promise of significantly improving the efficiency and performance of electric and hybrid cars, buses, trains and trams. Even everyday devices such as office copiers and cell phones benefit from the improved power delivery and long lifetimes of ultracapacitors.
Ruoff says significant implementation of wind farms for generation of electricity is occurring throughout the world and the United States, with Texas and California first and second in the generation of wind power.
According to the American Wind Energy Association, in 2007 wind power installation grew 45 percent in this country. Ruoff says if the energy production from wind turbine technology grew at 45 percent annually for the next 20 years, the total energy production (from wind alone) would almost equal the entire energy production of the world from all sources in 2007.
“While it is unlikely that such explosive installation and use of wind can continue at this growth rate for 20 years, one can see the possibilities, and also ponder the issues of scale,” he says. “Electrical energy storage becomes a critical component when very large quantities of renewable electrical energy are being generated.” ###
Funding and support was provided by the Texas Nanotechnology Research Superiority Initiative, The University of Texas at Austin and a Korea Research Foundation Grant for fellowship support for Dr. Park.
Ruoff's latest work to define the structure of graphite oxide appeared in the Sept. 26 issue of the journal Science. To read that story, go to: www.engr.utexas.edu/news/articles/.
For more information on Ruoff’s work, visit: bucky-central.me.utexas.edu/.
For more information, contact: Daniel J. Vargas, Cockrell School of Engineering, 512-471-7541, Daniel.vargas2@engr.utexas.edu; Rod Ruoff, Cockrell School of Engineering, 512-471-4691 or 847-370-4637, r.ruoff@mail.utexas.edu
About the Cockrell School of Engineering:
The Cockrell School ranks among the top ten engineering programs in the United States and aspires to move into the top five. With the nation's fourth highest number of faculty members elected to the National Academy of Engineering, the Cockrell School's more than 7,000 students work with many of the world's finest engineering educators and researchers. This environment prepares graduates to become engineering leaders and innovators working for the betterment of society.
Contact: Rod Ruoff r.ruoff@mail.utexas.edu 512-471-4691 University of Texas at Austin
Tags: Nano or Nanotechnology and Nanotech
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