Assembled and isolated Bi5O7I nanowires with good photocatalytic activities

Abstract

Assembled and isolated Bi5O7I nanowires were fast prepared through an aqueous strategy without further complex treatment. Powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV-vis diffuse reflectance spectroscopy (DRS) were used to characterize the obtained samples and reveal the evolution process of Bi5O7I nanomaterials. The formation of a hierarchical BiOI precursor and fast substitution of I− with OH− facilitated the evolution of assembled Bi5O7I architectures, while isolated Bi5O7I nanowires were obtained by shortening the existence time of BiOI crystals on the basis of assembled Bi5O7I nanowires. HRTEM results revealed similar crystalline orientations of nanowires along the [010] direction for the assembled and isolated Bi5O7I nanowire samples. And the nanowires in an assembled sample also exhibited a superlattice-like structure with a periodicity of 0.84 nm. On comparison to the BiOI precursor, the Bi5O7I nanowires with different assembly-styles all displayed good photocatalytic activities on the degradation of rhodamine B (RhB) dye and colorless bisphenol-A (BPA) under visible-light irradiation. The photocatalytic efficiency reached 96% in 3 h for RhB and 90% in 4 h for BPA in the degradation system at pH = 7. The assembled nanowire samples showed even better photocatalytic activities on the degradation of model organic pollutants relative to the isolated nanowire samples. Band structures and trapping experiments were studied to reveal the degradation mechanism over Bi5O7I nanowire samples. It was proposed that a valid separation of photogenerated electrons and holes and appropriate valence and conduction band positions of Bi5O7I nanowires led to good visible-light-induced catalytic properties.