Exploiting the chemistry of redox active compounds to enhance the capacitance of reduced graphene oxide

• Published in: FlatChem Vol. 15; p. 100108
• Main Authors: Bharathidasan, P., Balarabe Idris, Mustapha, Kim, Dong-Won, Sivakkumar, S.R., Devaraj, S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2019
• Subjects: Graphene; Improved capacitance; Redox active electrolyte; Redox couple; Reduced graphene oxide; Supercapacitor; Supercapacitor; Redox couple; Redox active electrolyte; Reduced graphene oxide; Graphene; Improved capacitance
• ISSN: 2452-2627; 2452-2627
• DOI: 10.1016/j.flatc.2019.100108

[Display omitted] •Addition of redox additives is a facile strategy to improve the capacitance of RGO.•Reversible redox reaction of quinone enhances the capacitance in H2SO4-Q electrolyte.•Shuttling of iodide and triiodide ions enhances the capacitance in H2SO4-KI.•In H2SO4-NaI electrolyte, formation of iodine also enhances the capacitance.•Slow kinetics of redox reactions slightly compromises the rate performance. The restacking of graphene sheets leading to poor electrical conductivity and reduced surface area strongly affects the capacitance properties of reduced graphene oxide (RGO). Many strategies employed to mitigate the restacking issue include the introduction of spacer materials between the graphene layers, hetero atom doping, compositing with metal oxides, etc. Herein, we report the enhancement of the capacitance properties of RGO by the addition of a small amount of redox active compounds, such as benzoquinone, KI, and NaI in the electrolyte. RGO is prepared by chemical exfoliation of graphite followed by a hydrothermal reduction in the presence of a small amount of hydrazine hydrate. The quality of prepared RGO is examined by microscopic and Raman spectroscopic studies. X-ray photoelectron spectroscopic studies reveal doping of 1.97 atomic weight % of nitrogen in RGO. The specific capacitance values of 105, 244, 322 and 414 F g−1 at a current density of 2 A g−1 are obtained for RGO in 0.25 M H2SO4 and 0.25 M H2SO4 containing 0.05 M of NaI, KI and benzoquinone, respectively. The enhancement in the specific capacitance of RGO is attributed to the reversible redox reaction of the additives. Interestingly, the mechanism of charge storage of RGO in NaI and KI containing electrolytes is different. Owing to rather slow kinetics of redox reaction of electrolyte additives, the rate performance of RGO has slightly compromised in redox active electrolytes.