Modulation of the Electrostatic and Quantum Capacitances of Few Layered Graphenes through Plasma Processing

Abstract

It is shown that charged defect generation, through argon ion-based plasma processing, in few layer graphene, could substantially enhance the electrical capacitance for electrochemical energy storage. Detailed consideration of the constituent space charge and quantum capacitances were used to delineate a new length scale, correlated to electrically active defects contributing to the capacitance, and was found to be smaller than a structural correlation length determined through Raman spectroscopy. The study offers insights into an industrially viable method (i.e., plasma processing) for modifying and enhancing the energy density of graphene-based electrochemical capacitors.

Plasma engineering of graphene

“…Which was deconvoluted to yield the Space-Charge Capacitance (C SC ) and the Quantum Capacitance (C Q ) with corresponding values of two-dimensional carrier density (n 2D,0 ), volumetric charge density (n), Fermi-velocity (ν F ) and the Fermi energy (E F ). 143 Reprinted with permission from Narayanan et al, Nano Lett. 15, 3067 (2015).…”

Defect Engineered 2D Materials for Energy Applications

“…Defects in material science and engineering are often perceived as performance limiters, but in the case of 2D materials, defect engineering could provide a way to overcome many roadblocks and forge new frontiers. In this regard, others and we have shown that defects in 2D materials (e.g., dopants, vacancies) can provide an excellent handle to control material properties [5][6][7][8]. Specifically, we have shown that defects such as vacancies and N dopants in graphene could be used to control the electron-electron and electron-phonon scattering pathways [8].…”

“…Specifically, we have shown that defects such as vacancies and N dopants in graphene could be used to control the electron-electron and electron-phonon scattering pathways [8]. These results provided critical breakthroughs for improving the quantum capacitance of graphene and doping graphene without compromising its intrinsic characteristics [6]. Defects also play a vital role in improving the properties of the so-called "beyond graphene" 2D materials.…”

“…Nanocarbons including carbon nanotubes and graphene have been widely used as an electrode in EDLCs due to their high surface area (~2000 m 2 /g), modest electrical conductivity, electrochemical stability, and open porosity [25,27]. However, the performance of the carbon-based EDLCs (particularly, graphene) is fundamentally limited by the so-called quantum capacitance (C q ), which is defined as C q = e 2 DOS(E F ) with e being the charge of an electron [6]. An intrinsically small DOS (E F ) in graphene results in a small serial C q , which diminishes the total device Two-dimensional Materials -Synthesis, Characterization and Potential Applicationscapacitance value (1/C meas = 1/C dl + 1/C q ) in EDLCs [6,28].…”

“…However, the performance of the carbon-based EDLCs (particularly, graphene) is fundamentally limited by the so-called quantum capacitance (C q ), which is defined as C q = e 2 DOS(E F ) with e being the charge of an electron [6]. An intrinsically small DOS (E F ) in graphene results in a small serial C q , which diminishes the total device Two-dimensional Materials -Synthesis, Characterization and Potential Applicationscapacitance value (1/C meas = 1/C dl + 1/C q ) in EDLCs [6,28]. Although graphene has high surface area and consequently high C dl , the total EDLC energy is limited by small C q .…”