Polymer-wrapped reduced graphene oxide/nickel cobalt ferrite nanocomposites as tertiary hybrid supercapacitors: insights from experiment and simulation

Abstract

The tertiary hybrid supercapacitor consisting of PEDOT:PSS wrapped reduced graphene oxide/Ni 0.5 Co 0.5 Fe 2 O 4 (PGNC) was developed and its supercapacitance performance has been compared with that of the reduced graphene oxide (rGO)/Ni 0.5 Co 0.5 Fe 2 O 4 (GNC), carbon nanotube (CNT)/Ni 0.5 Co 0.5 Fe 2 O 4 (CNC) and carbon nanotube/reduced graphene oxide/Ni 0.5 Co 0.5 Fe 2 O 4 (CGNC). Among all, PGNC exhibits an excellent specific capacitance of 1286 Fg −1 with a capacitance retention of 95% over 6000 cycles at a current density of 0.5 Ag −1 . The synergetic effects between rGO, Ni 0.5 Co 0.5 Fe 2 O 4 and the PEDOT:PSS polymer result in an increase in the specific surface area and the pore volume, making PGNC an excellent hybrid supercapacitor for energy storage. The enhancement in the specific capacitance of the PGNC nanocomposite is further validated through first-principles density functional theory calculations, which predict an increment in the density of states at the Fermi level of the GNC and CNC nanocomposites compared to the isolated Ni 0.5 Co 0.5 Fe 2 O 4 material. The supercapacitance performance of the PGNC nanocomposite is reported for different electrolytes, different stoichiometric ratios of Ni and Co in Ni x Co 1-x Fe 2 O 4 and on different substrates. • PGNC hybrid supercapacitor showed more specific capacitance than other supercapacitors. • The enhanced density of states and specific surface area reveals the more specific capacitance of PGNC. • The increase in specific surface area of PGNC was further corroborated by positron annihilation studies. • The effect of electrolyte and substrate on specific capacitance of PGNC was also studied.