Fabrication of hierarchical bismuth oxyhalides (BiOX, X = Cl, Br, I) materials and application of photocatalytic hydrogen production from water splitting

In this article, bismuth oxyhalides (BiOX) have been demonstrated to have remarkable photocatalytic activities due to their uniquely layered strusctures. Hierarchical BiOX (X: Cl, Br, I) microspheres were successfully synthesized by a microwave-assisted solvothermal method from bismuth (III) nitrate pentahydrate (Bi(NO3)(3)center dot 5H(2)O) using ethylene glycol and ethanol as solvents. The structures, morphology, and optical properties of the grown BiOX nanostructures were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), UV-visible diffuse reflectance spectra (DRS), electrochemical impedance spectroscopy (EIS), photoluminescence spectra (PL), and Brunauer-Emmett-Teller (BET) surface area. SEM revealed BiOX to have flower-like structures of microspheres and the as-synthesized photocatalysts were tested for the photocatalytic hydrogen evolution from water splitting via the irradiation of visible light. Among BiOXs as synthesized, BiOI can achieve the maximum hydrogen produciton rate (1316.9 mu mol h(-1) g(-1)) in 360 min under visible light irradiation because BiOI not only has a lowest PL intensity than the other BiOX group of materials to better separate the photogenerated electrons and holes, but also a sufficient over-potential of conduction band to achieve the conversion from H+ to H-2.