Comparing Graphite and Graphene Oxide Supercapacitors with a Constant Potential Model

Electric double-layer capacitors store energy because of the adsorption of ions on the surface of electrodes. A realistic model to describe the electrolyte-electrode interface is based on the constant potential method that allows the electrode charges to fluctuate in order to try to mimic the polarization of metallic electrodes [J. Phys. Chem. Lett. 2013, 4, 264-268]. We performed molecular dynamics simulations of graphene oxide (GO) electrodes using the constant potential model comparing carefully the interface structure, polarization, and charging processes of an ionic liquid with the respective properties calculated for graphite electrodes. The layered structure of the ions at the electrode-electrolyte interface is less organized in comparison with that observed for graphite electrodes, which reduces overscreening. With regard to performance in terms of energy storage, graphite performs better than GO in a wide range of applied voltages. The charging dynamics of GO is slower at low applied voltages. At high voltages, the stronger electrostatic interactions between the charged electrode and electrolyte prevail, allowing for similar charging times for both supercapacitors.

Automated summary

Electric double-layer capacitors store energy through the adsorption of ions on the surface of electrodes. Simulation results show that the charging dynamics are slower for graphene oxide electrodes at low applied voltages, but similar at high voltages when compared to graphite electrodes.