The effect of the synthesis conditions on structure and photocatalytic activity of Nb2O5 nanostructures

In this work, niobium pentoxide (Nb2O5) nanoparticles of varying sizes and morphology were synthesized using the controlled precipitation method. Ammonium niobate oxylate hydrate (NH4)H2[NbO(C2O4)3]· 3 H2O was used as a niobium precursor and distilled water or acetic acid was used as solvent. The obtained solids were characterized using Fourier transform infrared and Raman spectroscopies, X-ray diffraction and transmission electron microscopy. The as-synthesized solid precipitate was amorphous, but after heat treatment between 500 °C and 600 °C, the T-Nb2O5 phase was obtained. The size of the primary particles of the niobium pentoxide was nanometric (500 nm, when water was used as a solvent for synthesis. Considering the nature of the process, a possible reaction mechanism of the precursor with the water and NH4OH was proposed, which explains the formation of the solid within an aqueous solution. Considering one potential use of Nb2O5 synthesized in this work, the photo-degradation action of the particles on the organic molecule methylene blue was tested. The sample synthesized in acetic acid at pH ∼9.0 and heat treated at 600 °C showed the highest photo-degradation capacity, with a degradation of ∼60% of the dye for 60 minutes