Hierarchical nitrogen doped bismuth niobate architectures: Controllable synthesis and excellent photocatalytic activity

Nitrogen doped bismuth niobate (N-Bi ₃NbO ₇) hierarchical architectures were synthesized via a facile two-step hydrothermal process. XRD patterns revealed that the defect fluorite-type crystal structure of Bi ₃NbO ₇ remained intact upon nitrogen doping. Electron microscopy showed the N-Bi ₃NbO ₇ architecture has a unique peony-like spherical superstructure composed of numerous nanosheets. UV-vis spectra indicated that nitrogen doping in the compound results in a red-shift of the absorption edge from 450nm to 470nm. XPS indicated that [Bi/Nb]N bonds were formed by inducing nitrogen to replace a small amount of oxygen in Bi ₃NbO _7-xN _x, which is explained by electronic structure calculations including energy band and density of states. Based on observations of architectures formation, a possible growth mechanism was proposed to explain the transformation of polyhedral-like nanoparticles to peony-like microflowers via an Ostwald riping mechanism followed by self-assembly. The N-Bi ₃NbO ₇ architectures due to the large specific surface area and nitrogen doping exhibited higher photocatalytic activities in the decomposition of organic pollutant under visible-light irradiation than Bi ₃NbO ₇ nanoparticles. Furthermore, an enhanced photocatalytic performance was also observed for Ag/N-Bi ₃NbO ₇ architectures, which can be attributed to the synergetic effects between noble metal and semiconductor component.