Flexible and high-energy density asymmetrical supercapacitors based on polyindole/GCN/MnO2 nanocomposite for energy storage applications

In this study, an in situ oxidation polymerization approach and a surface adsorption procedure were combined to create a polyindole/graphitic carbon nitride (GCN)/manganese dioxide (MnO2) (Pin/GCN/MnO2) nanocomposite. This nanocomposite was used as an electrode for a supercapacitor. Investigations were made on the nanomorphology and crystal structure of MnO2, Pin/MnO2, GCN/MnO2, and Pin/GCN/MnO2. The developed Pin/GCN/MnO2 electrode-based supercapacitor's electrochemical performance was evaluated using cyclic voltammetry (CV) and AC impedance techniques in a 3 M KOH electrolyte. The Pin/GCN/MnO2 nanocomposite's average crystallite size is 40 nm. The Pin/GCN/MnO2 has a network of agglomerated GCN and Pin with extra spherical forms that are associated to MnO2 nanoparticles. Their absorption intensities improve with the development of the Pin/GCN/MnO2 nanocomposite. The specific capacitance of Pin/GCN/MnO2 in 3 M KOH was determined to be 1377 F/g at a current density of 5 A/g. The Pin/GCN/MnO2 electrode in KOH has average specific energy and specific power densities of 990 Wh kg−1 and 3305 W kg−1, respectively. Only 2% of the capacitance's initial value is lost after 10,000 cycles. The results illustrate the extraordinary stability and effective performance of the Pin/GCN/MnO2 electrode used in supercapacitors.