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

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) 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.

Automated summary

The addition of redox additives to traditional electrolytes can enhance the specific energy and electrochemical performance of supercapacitors. By adding [Fe(CN)6]3- and [Fe(o-phen)3]2+ to the NPGO electrode, a significant improvement in specific capacitance and specific energy was observed. Outer sphere electron transfer reactions play a key role in enhancing performance.