Sol-gel assisted morphology and phase dependent electrochemical performance of BiPO4 nanostructures for energy storage applications

Abstract

The present work reports the sol-gel-driven phase-dependent structural, optical, and electrochemical properties for monoclinic and hexagonal bismuth phosphate (BiPO4) nanostructures. The crystal structure symmetry distinction between the monoclinic and hexagonal BiPO4 phases was revealed by XRD, FTIR, and Raman spectroscopy. The XRD with Rietveld analysis infers the phase purity in the prepared samples. FESEM images showed the variation in diameter of the nanoplatelets as the temperature is increased. High-Resolution Transmission Electron Microscopy (HRTEM) provided accurate information on the morphology and size of the synthesized materials. The Selected area electron diffraction (SAED) pattern was used to understand the crystallinity of the samples. High-resolution TEM images allow us to see lattice planes, and calculation of lattice spacing was performed. Oxidation states and the composition of various elements in the material were confirmed by X-Ray Photoelectron Spectroscopy (XPS) spectra. The phase transformation from hexagonal and monoclinic BiPO4 structure is associated with the reaction medium of water-based interatomic distance and bond angle calculation. BiPO4 electrode having hexagonal phase demonstrates the excellent electrochemical evolution with improved specific capacity (~400.80 Cg−1) and longevity (~91.5% over 1100 cycles), respectively. The results analysis showed that morphology and Phase transition play a significant role in tuning the electrochemical performance of BiPO4 electrode, which implies that it could be a potential applicant for energy storage applications.