▎ 摘　　要

The aim of this work is to improve the electrochemical performance of graphene nanosheets for its potential applications as electrode materials in supercapacitors. In order to achieve this, we have carried out detailed ab - initio based density functional theory calculations on pristine and functionalized graphene nanosheets (containing 8, 18, and 32 carbon atoms) with different functional groups. We considered graphene nanosheets functionalized with groups such as ether, lactone, ketone, and carboxylate in addition to previously studied epoxy and hydroxyl. From the structural optimization, we observed variations in the transverse displacement of carbon atoms, changes in C-C and C-O bond length, and bond angles. In particular, we noticed when functionalized with lactone C-C and C-O bonds contracts more which results in excessive surface charge density, sigma and quantum capacitance, C-q:This suggest that C32 - functionalized with lactone would be a better candidate for battery electrodes with relatively high sigma and C-q values.