Combined Density Functional Theory and Molecular Dynamics Simulations To Investigate the Effects of Quantum and Double-Layer Capacitances in Functionalized Graphene as the Electrode Material of Aqueous-Based Supercapacitors

We report on DFT and MD simulations to investigate the contributions of quantum and double-layer capacitances in the total differential capacitance of functionalized graphene as the electrode material of aqueous-based supercapacitors. We consider the effects of nitrogen and oxygen incorporation in graphene quantum and double capacitance in four different supercapacitor models in the presence of aqueous electrolytes LiSO4 and LiTFSI. We found that the total differential capacitance is limited by the double-layer capacitance. Our best electrode/electrolyte model was obtained with a symmetric supercapacitor assembled with epoxy/hydroxyl-functionalized graphene electrodes filled with 1 M LiSO4 electrolyte. It achieved a higher double-layer capacitance among all investigated systems over the entire potential window, thus offering better performance in energy storage.

Automated summary

The study demonstrates that in aqueous-based supercapacitors, the double-layer capacitance plays a significant role in the total differential capacitance. A symmetric supercapacitor assembled with hydroxyl-functionalized graphene electrodes shows higher double-layer capacitance and better performance in energy storage.