Enhanced electrochemical performance of supercritical fluid aided P-doped graphene nanoflakes by I3-/I- redox couple

Heteroatom doped graphene framework is considered as a promising candidate for electrochemical hybrid supercapacitor applications. Herein, we report the synthesis of P-doped graphene using sodium phosphate as a phosphorus source by supercritical fluid assisted processing method. The chemical nature and the quantity of P-doping in graphene are analyzed using XPS and EDAX techniques. Three different P-doped graphene samples are prepared by varying the weight ratio of graphene oxide and sodium phosphate in which the P-doped graphene with a 1:1 weight ratio (graphene oxide: sodium phosphate) exhibits a high specific capacitance of 518 F/g and capacitance retention of 98% over 5000 cycles with 1 M H2SO4 electrolyte. Interestingly, there could be 4-fold increase in the specific capacitance is observed after the incorporation of KI with H2SO4 (1772 F/g) when compared with H2SO4 (396 F/g) at 4 A/g. In addition, specific energy of symmetric supercapacitor with KI/H2SO4 (29 Wh/kg) electrolyte is 3.4-fold higher than that of H2SO4 Wh/kg).

Automated summary

Heteroatom doped graphene framework shows promising potential for electrochemical hybrid supercapacitor applications. P-doped graphene synthesized using sodium phosphate showed high specific capacitance and capacitance retention, with further enhancements observed after incorporation of KI with H2SO4 electrolyte. The specific energy of symmetric supercapacitor with KI/H2SO4 electrolyte was significantly higher than that with H2SO4 electrolyte.