The effect of the synthesis temperature and duration on the morphology and photocatalytic activity of BiOX (X = Cl, Br, I) materials.

Abstract Bismuthoxyhalides photocatalysts (BiOX, X = Cl, Br, I) were prepared using solvothermal crystallization method. The influence of the synthesis temperature (120 °C, 140 °C, 160 °C) and duration (3 h, 24 h, 48 h) on the structural (crystal size, phase composition etc.), morphological (crystal shape), optical (bandgap values) parameters and on the resulting photocatalytic activity were investigated. The samples were characterized by the means of X-ray diffractometry (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the synthesized materials was evaluated under visible- (≥ 400 nm) and UV light (≈ 365 nm) by degrading methyl orange and Rhodamine B (RhB). The results pointed out the importance of the crystallization temperature and duration in achieving the highest photocatalytic activity, showing that the lowest temperature and the shortest duration time resulted the highest removal yields. Furthermore, a possible degradation mechanism was elaborated based on a direct hole oxidation approach and the detected degradation intermediates. Graphical abstract Unlabelled Image Highlights • The hydrothermal crystallization time tunes the efficiency of BiOX photocatalysts. • High synthesis temperature (160 °C) resulted Bi0, which inhibited the photoactivity. • The degradation products were identified, and direct hole oxidation mechanism was suggested. • The UV and the visible light degradation mechanism result different intermediate products. [ABSTRACT FROM AUTHOR]