Synthesis of novel hollow microflowers (NHMF) of Nb₃O ₇F, their optical and hydrogen storage properties

A two step, facile surfactant free hydrothermal route was adopted to synthesize Nb₃O₇F novel hollow microflowers (NHMF). Time dependent experiments were performed which suggested Nb₃O ₇F-NHMF were formed due to Ostwald-ripening process. Raman spectroscopy was conducted to understand different vibrational modes of Nb ₃O₇F-NHMF. Its characteristic band at 692 cm^-1 was observed which is associated to NbO₆ octahedron sharing. The bandgap of 3.2 eV was calculated by using UV-VIS-NIR absorption spectrum. Considering importance of layered structures in energy storage applications, hydrogen storage ability of Nb₃O₇F-NHMF were measured for the first time. The maximum values of hydrogen absorption for Nb ₃O₇F-NHMF at 373 K and 473 K were 0.789 wt.% and 1.08 wt.%, respectively. The hydrogen storage measurements revealed the potential of Nb₃O₇F-NHMF as prospective material for energy storage applications.