Architecture of superior hybrid electrode by the composition of Cu2O nanoflakes, novel cadmium ferrite (CdFe2O4) nanoparticles, and g-C3N4 sheets for symmetric and asymmetric supercapacitors

Transition metal oxides with carbon nanostructures are promising for energy storage devices because of their pseudocapacitance behavior with greater stability. In the present study, Cu2O nanoflakes (Cu2O) and CdFe2O4 nanoparticles (CdFe NPs) were placed on g-C3N4 sheets using a facile hydrothermal and wet impregnation processes. The synthesized hybrid composites were assessed as supercapacitors with symmetric and asymmetric setups. The electrochemical performance of pristine Cu2O, g-C3N4 sheets, and binary nanocomposites, such as Cu2O@CdFe NPs, Cu2O@g-C3N4, CdFe NPs@g-C3N4, were investigated using a traditional three-electrode system. The ternary nanocomposite possessed a 1067 F g(-1) specific capacitance at a 0.25 A g(-1) current density, which was similar to 4.2, 2.2, and 5.2 times higher than the Cu2O, CdFe NPs, and g-C3N4, respectively. The Cu2O-CdFe NPs@g-C3N4//Cu2O-CdFe NPs@g-C3N4 combination as a symmetric device showed a 120 F g(-1) specific capacitance at 0.25 A g(-1), which retained more than 50% of the specific capacitance at higher current densities (5 A g(-1)). Furthermore, the asymmetric device consisting of Cu2O-CdFe NPs@g-C3N4 as a cathode and activated carbon as an anode exhibited a specific capacitance of 140 F g(-1) at a current density of 0.5 A g(-1). This device was evaluated at an energy density of 31.25 Wh Kg(-1) at a power density of 478 W kg(-1), with strong cycling stability up to 4000 cycles (similar to 87% capacity retention). The superior composite structures can play a synergistic role between the materials, thereby improving their overall performance. The superior composition and their remarkable electrochemical performance suggest that the synthesized composite is favorable for supercapacitor applications.