Enhanced electrochemical performance of supercritical fluid treated N, P co-doped graphene by dual redox-additives

• Published in: Journal of power sources 2022-08, Vol.540, p.231587, Article 231587
• Main Authors: Sandhiya, Murugesan, Sathish, Marappan
• Format: Article
• Language: English
• Subjects: Flexible supercapacitor; Improved electrochemical performance; Outer sphere electron transfer; Redox-additive; Synergistic effect
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2022.231587

The low specific energy of carbon-based electrodes in aqueous electrolytes hampers the commercial application of supercapacitors (SCs). Redox-additive addition with conventional electrolyte is an efficient strategy to enhance the specific energy of SC. Here, we demonstrate the constructive synergistic effect and enhance the electrochemical performance by the addition of [Fe(o-phen)3]2+ with [Fe(CN)6]3-/H2SO4. The increase in the specific capacitance (Cs) of N, P co-doped graphene (NPGO) from 290 F g−1 in H2SO4 to 685 F g−1 by the addition of redox-additive [Fe(CN)6]3- with H2SO4. Further enhance in the Cs to 865 F g−1 has been observing by the addition of second redox-additive [Fe(o-phen)3]2+ with [Fe(CN)6]3-/H2SO4. The specific energy of flexible supercapacitor (FSC) uplift 3.6-times using [Fe(o-phen)3]2+(0.63 mM)+[Fe(CN)6](10 mM)/PVA/H2SO4 electrolyte than 6.8 Wh kg−1 of PVA/H2SO4. The enhance in Cs and specific energy has been noticing after the addition of [Fe(o-phen)3]2+ with [Fe(CN)6]3-/H2SO4 due to the outer sphere electron transfer reaction between [Fe(o-phen)3]2+ and [Fe(CN)6]3- with H2SO4. •N, P co-doped graphene (NPGO) prepared by supercritical method for the first time.•Synergistic effect of [Fe(o-phen)3]2+ and [Fe(CN)6]3- were observed.•High specific capacitance of 865 F g−1 obtained with dual redox-additive electrolyte.•Flexible supercapacitor fabricated using NPGO and redox-additive gel electrolyte.•High specific energy of 25 Wh kg−1 achieved with dual redox-additive electrolyte.