Ternary 3D reduced graphene oxide/Ni_0.5Zn_0.5Fe₂O₄/polyindole nanocomposite for supercapacitor electrode application

A facile two-step strategy has been reported for the preparation of a ternary 3D reduced graphene oxide/Ni_0.5Zn_0.5Fe₂O₄/polyindole nanocomposite (GNP) and this composite is applied as an electrode material for supercapacitor applications. Remarkably, Ni_0.5Zn_0.5Fe₂O₄ nanoparticles (NZF) decorated on reduced graphene oxide (GN2) are achieved by a facile hydrothermal method followed by coating with polyindole (PIN) through an in situ emulsion polymerization process. The structure, porosity, morphology, and thermal stability of the resulting ternary GNP hybrid material were characterized via X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurements, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). This combination of hybrid material has a favorable mesoporous structure that enables high exposure of active sites for fast electron transport for supercapacitor applications. We demonstrate here that the ternary GNP hybrid electrode material is capable of delivering a favorable specific capacitance of ∼320 F g^-1 at 0.3 A g^-1 within the potential range from -0.1 to 1 V, with desirable rate stability and excellent cycling stability in the three-electrode system. Furthermore, an asymmetric supercapacitor (ASC) of a two-electrode configuration was fabricated using 3D RGO and GNP as the negative and positive electrodes, respectively. Such a device manifests a favourable C _sp of 48.9 F g^-1 at 0.5 A g^-1 and retains stability of 84% even after 2000 cycles. This ASC device exhibits a significant energy density of 16.38 W h kg^-1 at a power density of 1784 W kg^-1. The synergistic effects of pseudo and double layer capacitive contributions from PIN and GN2 make this ternary GNP hybrid electrode material of great promise in supercapacitor applications.