By applying heat to a sheet of oxidized graphite(GO), the same material in carbon-based pencil lead, graphite becomes an electrically-conducting material called reduced graphite oxide (RGO). Researchers have been studying GO for the past decade, but a simple process developed by researchers at Rice University (Houston, TX) can turn sheets of graphite oxide into supercapacitors using a laser patterning chamber.

Supercapacitors are electrochemical capacitors that are much higher energy density than typical capacitors. Compared to batteries, they have much higher power density. Chemistry and biomechanical engineering professor Pulickel Ajayan and his team have discovered that when GO contains water, it acts as an ionic conductor. To build a fully functional supercapacitor, the RGO conducting electrode material is separated by RO, acting as an insulator that contains the electrolyte. Using a laser printer, the oxygen is sucked out of the GO creating RGO, with the pattern to nearly a one-micron accuracy. The device has the ability to store and release energy over thousands of cycles.

Ajayan says, "This process is so scalable that you could make a very large number of these in an array and collect them together, and ultimately, you could get pretty good power. But essentially, the focus if you look at single devices is at the micro scale."

The capacity of the thin, lightweight graphite film supercapacitor is the same as a commercially available supercapicitor with a thicker, cylindrical shape, so the printed version could be used in smaller, thinner devices. Possible applications include devices for use in fuel cells and lithium batteries. The study was published in the journal Nature Nanotechnology.