Increasing the Quantum Capacitance of Semiconducting C-Based Electrodes

The semiconducting character of graphene and C-based electrodes can significantly diminish the energy densities stored in ionic liquid-based electric double layer (EDL) capacitors. Extensive experimental research is currently dedicated to understand and modify the electronic structures of C-based electrode materials in order to increase their conductivity. Due to the presence of a Dirac point in graphene band structure and the low density of states near Fermi level, the quantum capacitance has a U-shaped dependence on gate voltage and low values for weakly charged electrodes. As a result of this quantum effects, the graphene electrode will generate U-shaped and low differential capacitance near potential of zero charge. The computational study presented here will show that it is possible to restore the metallic character of graphene and C-derived electrodes.  In this talk the coupling between EDL and quantum capacitances is considered for a number of C-based surfaces and room temperature ionic liquid electrolytes.   The concentration of doping, vacancies and edge and the geometric patterns that increase the quantum capacitance near Fermi level as well as their impact on total electrode capacitance will be discussed. The mechanism for increasing the quantum and total electrode capacitance will be explained based on the electronic structure/energy bands in electrode and the electrolyte structuring near the charged surface.