Route to achieving enhanced quantum capacitance in functionalized graphene based supercapacitor electrodes

Abstract

We have investigated the quantum capacitance (C<inf>Q</inf>) in functionalized graphene modified with ad-atoms from different groups in the periodic table. Changes in the electronic band structure of graphene upon functionalization and subsequently the C<inf>Q</inf> of the modified graphene were systematically analyzed using density functional theory (DFT) calculations. We observed that the C<inf>Q</inf> can be enhanced significantly by means of controlled doping of N, Cl and P ad-atoms in the pristine graphene surface. These ad-atoms are behaving as magnetic impurities in the system, generating a localized density of states near the Fermi energy which, in turn, increases charge (electron/hole) carrier density in the system. As a result, a very high quantum capacitance was observed. Finally, the temperature dependent study of C<inf>Q</inf> for Cl and N functionalized graphene shows that the C<inf>Q</inf> remains very high in a wide range of temperatures near room temperature. © 2019 Institute of Physics Publishing. All rights reserved.