Graphene for innovative energy storage

Supercapacitors are similar to batteries in that both store electric charge. However, supercapacitors store charge in the form of static electricity, rather than relying on chemistry. While batteries can store a lot of energy and release it over a fairly long time, supercapacitors are typically known for rapid energy release and are better suited for technologies where smaller amounts of energy are needed quickly, such as mobile electronics.

The UT-Austin material’s processing techniques are already readily scalable to industrial production and have the potential to improve energy storage and conversion technologies, from electric cars to expanding power availability from wind power and solar energy sources.

The UT-Austin team first created a more porous form of carbon by using potassium hydroxide to restructure graphene platelets. They found that the new material was superior to others typically used in supercapacitors. With that in mind, they turned to Brookhaven for help with further structural characterization of the material. BNL materials scientist Eric Stach and his team conducted a wide range of studies detailing the carbon walls and pore structure of the material.

Stach explained, “At the DOE laboratories, we have the highest resolution microscope in the world, so we really went full bore into characterizing the atomic structure.”

In other graphene news, physicists at the Department’s Lawrence Berkeley National Laboratory and their colleagues at the University of California-Berkeley, Stanford University and other institutions have the made the first precise measurements of the “edge states” of nanoribbons.

These nanoribbons are strips of graphene that may be only a few nanometers wide (a nanometer is a billionth of a meter). In the past, theorists envisioned that nanometers, depending on their width and the angle at which they’re cut, would have unique electronic, magnetic and optical features, but were unable to test these predictions until now.

Through scanning tunneling microscopy, the team measured electronic density changes on the nanoribbon edge. They discovered that electrons are confined to the edge of the ribbons, and that these nano-ribbon edge electrons exhibit significant differences in their energy levels.

The next step is figuring out how to control these edge states – the potential applications of are wide-ranging, from energy-efficient nanoscale devices to advanced photovoltaics and spintronics.

By Niketa Kumar, public affairs specialist in the Office of Public Affairs, blog.energy.gov/