Template-free synthesis of 3D Nb3O7F hierarchical nanostructures and enhanced photocatalytic activities

Abstract

Single-crystalline niobium oxide fluoride (Nb₃O₇F) hierarchical nanostructures are firstly prepared via a facile hydrothermal method without using any template or surfactant. The results of scanning electron microscopy and transmission electron microscopy showed that the hierarchical morphology of Nb₃O₇F could be effectively controlled by adjusting the reaction time. Ultraviolet-visible spectra showed that such nanostructures have a narrow absorption peak at around 400 nm compared to Nb₂O₅. Based on the first-principles plane-wave ultrasoft pseudo potential (USPP) method, the crystal structures of Nb₃O₇F was optimally calculated for the total density of states (TDOS) and the partial density of states (PDOS) of Nb, O and F atoms. According to the observations of architectures formation, a possible growth mechanism was proposed to explain the transformation of nanoparticles to hierarchical nanostructures via an Ostwald ripening mechanism followed by self-assembly. In particular, the excellent photocatalytic activity of the Nb₃O₇F hierarchical nanostructures was confirmed by photodegradation of methylene blue, methyl orange and rhodamine B molecules.