Capacitance comparison of poly(indole-5-carboxylic acid) in different electrolytes and its symmetrical supercapacitor in HClO4 aqueous electrolyte

• PICA nanowires were prepared by a one-step electrodeposition method.
• Capacitance performances of PICA in different electrolytes were researched.
• HClO4 electrolyte can improve the capacitance performance significantly.
• The reason of the high performance of PICA in HClO4 was proposed.

In this work, poly(indole-5-carboxylic acid) (PICA) nanowires were facilely prepared by a one-step electrodeposition on glass carbon electrode (GC) and its capacitance performance was evaluated in different electrolytes. The initial galvanostatic charge/discharge test of PICA in acetonitrile/LiClO4 exhibited a specific capacitance of 275 F g−1 at the current density of 1.0 A g−1 but the capacitance stability was quite poor, whereas, an enhanced specific capacitance (350 F g−1 at 1.0 A g−1) and an improved capacitance stability (98% capacitance retention after 1000 cycles) were obtained in HClO4 aqueous electrolyte, which were also better than that in the counterpart media (Na2SO4, KCl, and H2SO4 aqueous electrolytes). Additionally, the symmetrical supercapacitor based on two PICA electrodes in HClO4 aqueous electrolyte exhibited a maximum specific capacitance of 69.0 F g−1, an energy density of 9.4 Wh kg−1 at a power density of 1000 W kg−1, and an excellent cycle life of 94% specific capacitance retention after 1000 cycles. These results implied that the PICA nanowires with HClO4 aqueous solution as electrolyte will be a kind of promising electrode material for supercapacitors.