Fabrication Of Nb₂O₅-based Microfibers And Their Photocatalytic Properties

Semiconductor-based photocatalysis has been extensively investigated for pollution treatment. Niobium oxide(Nb2O5) is a candidate of new generation photocatalyst. Low quantum efficiency and relatively narrow light absorption range limit its in practical application. In this thesis,biomorphic Nb2O5 fibres with different crystal structure and Nb2O5/Ag PO4 composite have been prepared. The phase composition, mophology, photocatalitic properties have been sysytematically investigated.Firstly, biomorphic hollow Nb2O5 fiber with hexagonal and orthorhombic structures have been prepared using cotton as template.. Results show that biomorphic Nb2O5 fibers are both hollow and porous walls. This architectures is helpful to improve the specific surface area of the catalyst. Photocatalytic activity of Nb2O5 fiber was evaluated through degradation of methylene blue(MB) in aqueous solution exposed to UV light. Photocatalytic activity of physically mixed fibers with 75% H-Nb2O5 and 25% O-Nb2O5 phases is superior to that of pure H- and O- Nb2O5 phases, and other hybrid fibers photocatalyst. Such superior photocatalytic activity is mainly due to optimal balance between the adsorption of MB, the oxidation property and the absorption of UV light. Moreover, the large size of Nb2O5 hollow fibers could be easily separated from the solution.Secondly, micrometer Nb2O5 fibers with wrinkling surface was fabricated by improved method. The Ag3PO4/Nb2O5 ?ber composites was fabricated by in situ depositing Ag3PO4 nanoparticles onto the Nb2O5 ?bers surface through a facile deposition precipitation technique. Results show that special morphology of Nb2O5 fibers not only modified larger specific surface area than above-mentioned sample, but also large voids and interfaces in favour of loading nanosized particles. The photocatalytic activity of Ag3PO4/Nb2O5 composites was evaluated by the photocatalytic degradation of Rh B under visible light. The improved activity of the Ag3PO4/Nb2O5 with equal molar photocatalyst exhibited much higher photocatalytic activity than pure Ag3PO4 and other Ag3PO4/Nb2O5 ?ber composites. The heterojunction between Ag3PO4 with Nb2O5 semiconductor decreases recombination probability of the photo-generated electron–hole pairs and enhances photocatalytic efficiency. The Ag3PO4/Nb2O5(molar ratio=1:1) samples has almost no loss of photocatalytic activity after four recycles under the irradiation of visible light, indicating that the composite has good photocatalytic stability. Moreover, the large size of the Ag3PO4/Nb2O5 composite allows them to be easily separated from the solution.