Regular Article Bismuth oxyfluoride/bismuth oxyiodide nanocomposites enhance visible-light-driven photocatalytic activity Chiing-Chang Chen ⇑ , Jing-Ya Fu, Jia-Lin Chang, Shiuh-Tsuen Huang, Tsung-Wen Yeh, Jiun-Ting Hung, Peng-Hao Huang, Fu-Yu Liu, Li-Wen Chen ⇑ Department of Science Education and Application, National Taichung University of Education, Taichung 403, Taiwan graphical abstract Schematic of the band-gap structures of BiOF/BiOI and the possible charge separation processes. article info Article history: Received 10 June 2018 Revised 26 July 2018 Accepted 29 July 2018 Available online 3 August 2018 Keywords: BiOF BiOI Nanocomposites Photocatalytic Crystal violet 2-Hydroxybenzoic acid abstract This is the first paper to report a series of bismuth oxyfluoride/bismuth oxyiodide (BiO p F q /BiO x I y ) nanocomposites with different F/I molar ratios, pH values, and reaction temperatures that were synthe- sized through a template-free and controlled hydrothermal method. These nanocomposites were charac- terized through scanning electron microscope energy dispersive microscopy (SEM-EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), X-ray photoelec- tron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), and diffuse reflectance spectroscopy (DRS). Under visible-light irradiation, the BiO p F q /BiO x I y 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 com- posites were determined to be adequate under visible-light irradiation. For various scavengers, the noted quenching effects demonstrated that reactive O 2 Å has a notable role in the degradation of the applied CV. Ó 2018 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jcis.2018.07.130 0021-9797/Ó 2018 Elsevier Inc. All rights reserved. ⇑ Corresponding authors. E-mail addresses: ccchen@mail.ntcu.edu.tw (C.-C. Chen), liwenchen@mail.ntcu.edu.tw (L.-W. Chen). Journal of Colloid and Interface Science 532 (2018) 375–386 Contents lists available at ScienceDirect Journal of Colloid and Interface Science journal homepage: www.elsevier.com/locate/jcis