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

Graphical abstract: Efficient visible-light-driven photocatalysts of peony-like nitrogen doped Bi3NbO7 hierarchical architectures and silver-layered Bi3NbO7−xNx heterostructures were successfully synthesized in this discovery. Highlights: ► N-Bi3NbO7 architectures were synthesized via two-step hydrothermal process. ► Electronic structure calculations indicated that N replaced O in samples. ► Growth mechanism is proposed for transformation of nanoparticles to microflowers. ► Excellent activities of N-Bi3NbO7 architectures were obtained for degradation. ► Enhanced photocatalytic performance was observed for Ag/N-Bi3NbO7 architectures. - Abstract: Nitrogen doped bismuth niobate (N-Bi3NbO7) hierarchical architectures were synthesized via a facile two-step hydrothermal process. XRD patterns revealed that the defect fluorite-type crystal structure of Bi3NbO7 remained intact upon nitrogen doping. Electron microscopy showed the N-Bi3NbO7 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 450 nm to 470 nm. XPS indicated that [Bi/Nb]-N bonds were formed by inducing nitrogen to replace a small amount of oxygen in Bi3NbO7−xNx, 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-Bi3NbO7 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 Bi3NbO7 nanoparticles. Furthermore, an enhanced photocatalytic performance was also observed for Ag/N-Bi3NbO7 architectures, which can be attributed to the synergetic effects between noble metal and semiconductor component.