<p>In this work, a bifunctional SiO₂-NiCo₂O₄ three-dimensional octahedral morphology nanocomposite was synthesised by a simple co-precipitation method for photocatalytic and supercapacitor applications. The phase formation, optical properties and morphology of the obtained materials were characterized by various analytical methods such as XRD, FTIR, FESEM, HR-TEM and XPS. The samples catalytic efficiency in the breakdown of methylene blue (MB) dye was studied. The effects of various process parameters on the extent of dye removals such as photocatalyst amount, irradiation period, the concentration of dye and pH of the solution were also studied. In addition, Galvanostatic charge-discharge (GCD), Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) were used to analyse their electrochemical performance. The fabricated electrodes NiCo₂O₄ and SiO₂-NiCo₂O₄ exhibited pseudocapacitive behaviour due to their Faradic Redox properties within the potential range from 0.0 to 0.6&#xa0;V and obtained a high specific capacitance of 1001&#xa0;F g^− 1 for NiCo₂O₄ and 1538&#xa0;F g^− 1 for SiO₂-NiCo₂O₄ at an applied current density of 1&#xa0;A g^− 1 from GCD curve respectively, with retention of 87.4% for NiCo₂O₄ and 90% for SiO₂-NiCo₂O₄ of capacitance even after 5000 cycles at 7&#xa0;A g^− 1 and with the coulombic efficiency of 90% for NiCo₂O₄ and 95% for SiO₂-NiCo₂O₄. The fabricated SiO₂-NiCo₂O₄ electrode showed a strong reduction in the Rct (0.9) value than the pristine nanocomposites. This work may inspire the octahedral architecture of bifunctional nanocomposite materials to achieve high performance in cross-field applications.</p> Graphical Abstract <p>Graphical abstract shows the performance of SiO2-NiCo2O4 nanocomposites electrode.</p> <p></p>