Rational Design of Cobalt Oxide–Iron Oxide Nanoparticle-Embedded Sodium Alginate Membranes for Supercapacitors

Abstract

The growing demand for sustainable, flexible, and high-performance electrode materials for energy storage has motivated the development of polymer-based composite electrodes with enhanced electrochemical properties. In this study, flexible cobalt oxide (Co3O4)-iron oxide (Fe2O3) nanoparticle-impregnated sodium alginate (NaAlg) as the polymer matrix composite membranes were developed via a simple solution-casting method to exploit the synergistic pseudocapacitive behaviour of mixed metal oxides together with the excellent film-forming ability, flexibility, and eco-friendly nature of NaAlg. The prepared membranes’ structural features, morphology, and electrochemical properties were examined through a set of techniques, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Universal Testing Machine (UTM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation (PDP), and galvanostatic charge–discharge (GCD). Characterisation techniques validated the effective loading of Co3O4 and Fe2O3 nanoparticles within the NaAlg matrix, and revealed the efficient interfacial interactions, structural integrity, and electrochemical properties of the composites. GCD tests showed a very high specific capacitance of 571.43 F g−1 at 1.2 A g−1. The best-performing electrode produced a top energy density of 155.56 Wh kg−1 at a power density of 2800 W kg−1 and still showed around 91% capacitance retention after 2500 charging–discharging cycles with coulombic efficiency close to 100%. Boosted electrochemical performance is due to the synergistic effect of Co3O4-Fe2O3 nanoparticles that not only offer plenty of electroactive sites but also help in effective electron and ion transport within the polymer matrix. The results obtained here confirmed the capabilities of Co3O4-Fe2O3@NaAlg composite membranes as green and potent electrode materials for future supercapacitor devices.