Shiuh-Tsuen Huang

Hydrothermal synthesis of bismuth oxybromide–bismuth oxyiodide composites with high visible light photocatalytic performance for the degradation of CV and phenol

This is the first report on a series of BiOpBrq/BiOmIn heterojunctions that were prepared using controlled hydrothermal methods. The compositions and morphologies of the BiOpBrq/BiOmIn could be controlled by adjusting some growth parameters, including reaction pH value, temperature, time, and KBr/KI molar ratio. The photocatalytic efficiency of the powder suspensions was evaluated by measuring crystal violet (CV) and phenol concentrations. Both the photocatalytic process and the photosensitized process were found to work concurrently. The quenching effects of various scavengers and EPR indicated that the reactive O2˙− played a major role and ˙OH and h+ played minor roles. The photocatalytic activity of the BiOpBrq/BiOmIn heterojunctons reached the maximum rate constant of 0.5285 (or 0.4713) h−1, 10 times higher than that of P25–TiO2, 14 times higher than that of BiOBr, and 6 times higher than that of BiOI.

Bismuth oxyfluoride/bismuth oxyiodide nanocomposites enhance visible-light-driven photocatalytic activity

This is the first paper to report a series of bismuth oxyfluoride/bismuth oxyiodide (BiOpFq/BiOxIy) nanocomposites with different F/I molar ratios, pH values, and reaction temperatures that were synthesized through a template-free and controlled hydrothermal method. These nanocomposites were characterized through scanning electron microscope energy dispersive microscopy (SEM-EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and diffuse reflectance spectroscopy (DRS). Under visible-light irradiation, the BiOpFq/BiOxIy composites exhibited excellent photocatalytic activities in the degradation of crystal violet (CV) and 2-hydroxybenzoic acid (HBA). The order of rate constants was BiOF/BiOI > BiOI ≫ BiOF. The photocatalytic activity of BiOF/BiOI composites reached a maximum rate constant of 0.2305 h-1, 1.2 times higher than that of BiOI and 100 times higher than that of BiOF. Thus, the derived BiOF/BiOI is crucial for photocatalytic activity enhancement. After the removal of CV in the third cycle, no apparent deficits in photocatalytic activity were observed, and the observed deficit was 8.2% during the fifth run. Overall, the catalytic activity and stability observed for the proposed composites were determined to be adequate under visible-light irradiation. For various scavengers, the noted quenching effects demonstrated that reactive O2- has a notable role in the degradation of the applied CV.