Comparing Graphite and Graphene Oxide Supercapacitors with a Constant Potential Model

Abstract

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.

EDL structure of ionic liquid-MXene-based supercapacitor and hydrogen bond role on the interface: a molecular dynamics simulation investigation

“…6b. 64 As described above, this hydrogen bonding interaction has resulted in more HEMIm + aggregating on the Ti 3 C 2 (OH) 2 surface (Fig. 4).…”

“…Compared with most of the reported carbon-based EDL supercapacitors, the MXene-based EDL supercapacitors have better energy storage performances. 64,66,67 The capacitance values we calculated for both MXene electrodes are above 5 μF cm −2 , especially the MXene with the hydroxyl terminal. However, the capacitance values of graphene oxide calculated by MD simulation are around 4 μF cm −2 .…”

“…The EIA near the Ti 3 C 2 (OH) 2 is smaller than that near the Ti 3 C 2 O 2 , indicating that the hydroxyl terminations on the MXene electrodes play a role in reducing the overscreening. 64…”

“…However, the capacitance values of graphene oxide calculated by MD simulation are around 4 μF cm −2 . 64 This provides a promising prospect for designing supercapacitors with a high energy and high power density.…”

Improving electrochemical performance of hybrid electrode materials by a composite of nanocellulose, reduced oxide graphene and polyaniline

“…For EDLCs, because electrode materials oen require high porosity, high surface area, and high electron conductivity, much research effort has been focused on developing carbonaceous materials, for example, aerogel carbon, 5 carbon nanotube (CNT), 6,7 graphene, 8 reduced graphene oxide, 7 graphite. 9 Regarding PDs, due to their charge storage mechanism relying on three processes, including underpotential deposition, redox pseudocapacitance, and intercalation pseudocapacitance; the electrode active materials are novel metals, 10,11 metal transition oxides, 12,13 conducting polymers. 13,14 However, the EDLCs and PDs suffer their own disadvantages, such as low specic capacitance (as for EDLCs) and low cycle life (as for PDs).…”