Electrochemical performance of polypyrrole derived porous activated carbon-based symmetric supercapacitors in various electrolytes

Abstract

The electrochemical performance of porous carbon prepared from the polymerization and carbonization of pyrrole is presented in this work. The produced carbon exhibited a high specific surface area and high mesopore volume that are desirable and beneficial for high capacitive performance. Symmetric supercapacitor devices fabricated from this carbon were tested in three different electrolytes (6 M KOH, 1 M NaNO₃, and 1 M Na₂SO₄). Higher capacitive performance (specific capacitance of 131 F g⁻¹) in the 1 M Na₂SO₄ medium was obtained compared to the other two electrolytes a with specific capacitance of 108 F g⁻¹ in 6 M KOH and 94 F g⁻¹ in 1 M NaNO₃ respectively. The difference observed in capacitance in the three electrolytes is linked to the individual properties of the electrolytes which include the conductivity and different ion solvation sizes. A potentiostatic floating test at the maximum voltage for 140 h was used to study the stability of the devices and from the experimental data, a 7% capacitance decrease was observed in the 6 M KOH electrolyte which is related to the corrosive atmosphere and oxidation of the positive electrode. A decrease of 18% in capacitance was observed in 1 M NaNO₃ with an increase in resistance and 1% capacitance decay was observed in 1 M Na₂SO₄ with no change in resistance value at the end of the floating test. These results suggest the good performance of the polypyrrole based activated carbon for symmetric supercapacitors in aqueous electrolytes in general with 1 M Na₂SO₄, in particular, showing excellent stability after floating.