CoFe2O4 nanocubes over Cu/graphitic carbon nitride as electrode materials for solid-state asymmetric supercapacitors

• A novel ternary composite CoFe 2 O 4 /Cu/g-C 3 N 4 was proposed for hybrid supercapacitor. • CoFe 2 O 4 nanocubes were decorated over Cu/g-C 3 N 4 via a facile synthesis process. • CoFe 2 O 4 /Cu/g-C 3 N 4 exhibited a high specific capacitance of 1380F/g at 1 A/g. • CoFe 2 O 4 /Cu/g-C 3 N 4 offered 86.4 % capacity retention after 10,000 cycles at 10 A/g. • Designed ASC device showed 144.4 Wh/kg energy density at 7.992 kW/kg power density. Increasing the energy density of supercapacitors without compromising power density, cycle stability, or other vital factors remains a major challenge. The present work demonstrates the successful synthesis of a novel ternary CoFe 2 O 4 /Cu/g-C 3 N 4 nanocomposite, where the CoFe 2 O 4 nanocubes were synthesized using a hydrothermal method and Cu nanoparticles were grafted in holey g-C 3 N 4 sheets with in-situ chemical co-precipitation technique. The as-synthesized ternary nanocomposite withstands high temperature and exhibits an outstanding high energy density and cyclic stability along with significant power density. Different electrochemical methods were extensively performed, and the electrochemical measurements unveiled that CoFe 2 O 4 /Cu/g-C 3 N 4 exposes greater specific capacitance of 1380F/g at 1 A/g with 86.4 % capacity maintenance after 10,000 cycles at 10 A/g. Moreover, the designed solid-state asymmetric supercapacitor with the ternary composite offers an energy density of 144.4 Wh/kg at 7.992 kW/kg power density. This accretive improvement of the overall electrochemical behaviors of CoFe 2 O 4 /Cu/g-C 3 N 4 paralleled to its components is credited to the synergistic phenomenon among CoFe 2 O 4 and Cu nanoparticles over the g-C 3 N 4 nanosheets in alkali medium, thus offering a novel promising ternary electrode material for hybrid supercapacitors.