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 (CA) 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.