Enhancing photocatalytic activity by tuning the ratio of hexagonal and orthorhombic phase Nb2O5 hollow fibers

Abstract

Cotton was used as template for the fabrication of a biomorphic Nb₂O₅ photocatalyst with hexagonal and orthorhombic structures. The as-prepared Nb₂O₅ was characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area and UV-Vis diffused reflectance spectra measurements. The photocatalytic activity of the Nb₂O₅ fibers was evaluated through degradation of methylene blue (MB) in aqueous solution exposed to UV light. SEM results show that biomorphic Nb₂O₅ fibers are both hollow and have porous walls. The architectures allow a more accessible surface for the photocatalytic decomposition of dyes molecules. The photocatalytic activity of physically mixed fibers with 75% H-Nb₂O₅ and 25% O-Nb₂O₅ phases is superior to those of pure H- and O-Nb₂O₅ phases, and other samples with different H- and O-Nb₂O₅ ratios. Such superior photocatalytic activity is mainly due to an optimal balance between the adsorption of MB and the absorption of UV light. Moreover, the large size of the Nb₂O₅ hollow fibers allows them to be easily separated from the solution.