Synergistic effects of niobium phosphate/tungsten oxide core-shell nanocomposites for asymmetric supercapacitor

The energy requirements of modern civilization necessitate the use of efficient renewable energies. Therefore, this research assessed the effectiveness of newly developed niobium phosphate (NbPO₅)/tungsten oxide (WO₃) core-shell nanocomposite thin film electrodes fabricated through a combination of facile hydrothermal synthesis with electrodeposition method as promising energy storage devices. The investigation involved a thorough analysis of the optimization of reaction time for NbPO₅ to explore the resulting modifications in their structural, morphological, and energy storage properties. Raman spectroscopy offers a detailed exploration of vibrational modes and structural characteristics while, X-ray photoelectron spectroscopy (XPS) spectra provide comprehensive information on the chemical composition, elemental state, and surface properties. NbPO₅/WO₃ core-shell electrode presented variable surface morphologies in accordance with the different synthesis times. The optimized NbP-W-6 sample demonstrated excellent energy storage performance, with a high areal capacitance of 5.97 F/cm² at a current density of 20 mA/cm² and energy density of 0.406 mWh/cm² at a power density of 7 mW/cm². Moreover, the NbP-W-6 sample exhibited outstanding long-term cycling stability, retaining 84.63 % of its total capacitance throughout 12,000 consecutive cycles. The remarkable energy storage capacity of the NbP-W-6 is attributed to its enhanced diffusion rate, higher charge transfer efficiency, and improved carrier mobility facilitated by the core-shell structure that combines the stability of NbPO₅ with the high conductivity of WO₃. The assembled asymmetric pouch-type supercapacitor device (APSD) achieves an areal capacitance of 759.0 mF/cm² at a current density of 30 mA/cm². Through highly competitive electrochemical performance, our findings reveal that core-shell nanocomposites deposited directly onto Ni-foam, opening up potential applications in energy storage.