Exploring the electrochemical performance of niobium phosphate electrode for supercapacitor application

This study assessed the suitability of niobium phosphate (NbPO₅) thin films for energy storage applications. The NbPO₅ thin films were synthesized using a hydrothermal technique for various deposition times. The structural, morphological, elemental, and electrochemical characteristics of the NbPO₅ thin films were analyzed. The NbPO₅ thin films had an orthorhombic crystal structure with a unique surface morphology consisting of tetragonal-shaped micro-rods surrounded by nanostructured spheres. X-ray photoelectron spectroscopy and energy dispersive spectroscopy confirmed the NbPO₅ composition. The micro-rods and nanospheres morphology of NbPO₅ samples at 6 h deposition time (NbP-6) exhibited a high areal capacitance (C_A) of 3542.4 mF cm⁻² at a current density of 10 mA cm⁻². The excellent energy storage performance of the NbP-6 sample was attributed to the high diffusion coefficient, enhanced charge transfer, and carrier mobility. Moreover, the NbP-6 sample displayed excellent long-term cycling stability, maintaining 85.4% of its total capacitance and 98.7% of coulombic efficiency over 10,000 consecutive galvanostatic charge-discharge cycles. The present study suggests that an NbPO₅ electrode is a promising candidate for supercapacitor applications owing to the synergistic effects of niobium and phosphate.