Prabhakar Bandaru, University of California, San Diego, La Jolla, CA, USA, and colleagues have used argon-ion based plasma processing as a methode to increase the amount of electric charge that can be stored in graphene. They bombarded graphene samples with positively-charged argon ions which knocked carbon atoms out of the graphene layers and left positively charged holes behind. These defects were characterized with Raman spectroscopy and electrochemical measurements.

The researchers found that extended defects had been formed. Based on the configurations of the missing carbon atoms, these are named as “armchair” and “zigzag” defects. The generation of the charged defects resulted in a three-fold increase of the electrical capacitance for electrochemical energy storage.

The researchers think that their study may provide a better understanding of how to improve the energy storage ability of capacitors.

• Modulation of the Electrostatic and Quantum Capacitances of Few Layered Graphenes through Plasma Processing,
  R. Narayanan, H. Yamada, M. Karakaya, R. Podila, A. M. Rao, P. R. Bandaru,
  Nano Lett. 2015.
  DOI: 10.1021/acs.nanolett.5b00055