Sorption-photocatalytic performance of NbOx nanocrystals synthesized via heat-stimulated oxidation of niobium carbide

In this work, nano-sized niobium oxides with different crystal structures can be produced by thermal treatment ofnonstoichiometric nanocrystalline niobium carbide (NbCy) and serve as effective sorbents and photocatalyticmaterials. Differential thermal analysis of initial NbCy powder was carried out, and temperatures of thermaltreatment for the were chosen. The nanopowders were studied using powder X-ray diffraction, scanning electronmicroscopy, low-temperature N2 adsorption–desorption, X-ray photoelectron spectroscopy and diffuse reflectanceelectron spectroscopy methods. The specific surface area of samples annealed at 100, 200, 300, 400, 500 ◦Cwas about 224, 255, 273, 224 and 47 m2/g, respectively. The photocatalytic activity of the obtained nanopowderswas analyzed during the oxidation of an aqueous solution of methyl orange on exposure to visible light.The photocatalytic activity of nanopowders grows with the annealing temperature increasing from 100 to 500 ◦Cand reaches the maximum value for the higher niobium oxide Nb2O5. The time of complete decoloration of dyewas 165 min. The tests performed to establish the sorption equilibrium between catalyst and dye in the darkrevealed that the nanopowder produced during annealing at 300 ◦C possesses a high sorption capacity of 76.5%,which allows it to be considered as an effective sorbent.