The interfacial capacitance of graphene, the fundamental building block of carbon based high surface area electrodes, is limited by its quantum capacitance (C_Q).^1,2 We will show that the C_Q of single-layer and few-layer graphene can be increased, e.g., through doping using specific plasma processing techniques. We will first show that the density of states and consequently the carrier concentration of graphene can be increased via argon based plasma processing.³ Subsequently, we will suggest ways to modulate the effective doping (both, p- and /n- type) through subjecting the graphenes to plasmas consisting of differently charged ions (Argon and Nitrogen).  We will indicate extensive Raman spectroscopy and electrochemical characterization, to clearly elucidate the nature of plasma doping and its effect on the quantum capacitance.⁴ The implications of plasma processing to the resistance change and the power density of graphene based electrochemical capacitors will be indicated. The work is of considerable scientific and technological interest.⁵, in terms of evaluating the underlying charge storage mechanisms of graphene for potential use in energy storage devices.

References:

1. J. Xia, F. Chen, J. Li, and N. Tao, Nat. Nanotechnol., 4, 505–509 (2009).

2. H. Yamada and P. R. Bandaru, Appl. Phys. Lett., 102, 173113 (2013)

3. R. Narayanan et al., Nano Lett., 15, 3067–3072 (2015).

4.  A.Das et al., Nat. Nanotechnol., 3, 210–215 (2008).

5. L. L. Zhang et al., Energy Environ. Sci., 5, 9618 (2012).