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

Abstract

We have investigated the quantum capacitance (CQ) 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 CQ of the modified graphene were systematically analyzed using density functional theory (DFT) calculations. We observed that the CQ 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 CQ for Cl and N functionalized graphene shows that the CQ remains very high in a wide range of temperatures near room temperature. 2019 Institute of Physics Publishing. All rights reserved.