Synthesis, characterization and photoactivity of BiOCl _1−x I _x nanostructures by hydrothermal method using bismuth acetate

Abstract Bismuth oxyhalides (BiOX, X = Cl, Br, I) have gained relevance during the last two decades for applications in photocatalysis degrading organic compounds. It is important to note that almost every existing report on the synthesis of bismuth oxyhalides declare the use of nitrate as bismuth source, either via precipitation, hydrothermal synthesis or other methods. In this work, BiOCl 1−x I x (x = 0, 0.25, 0.5, 0.75, 1) nanomaterials were synthesized through a hydrothermal process, using bismuth acetate as Bi precursor in water-based solutions, at 160 °C. All the obtained samples consisted of micrometric particles (∼ 1–3 μm) assembled with nanosheets (∼ 10–40 nm thickness), as observed from SEM images. They showed coloration shifting from white, through yellow and orange tones, to red with the increase of iodine content; this is explored for correlation with I/Cl concentration ratio, which is consistent with the energy gap (E g ) determined from Tauc plots as an indirect transition, with values varying from 3.4 eV (x = 0) to 1.81 (x = 1). The desired tetragonal phase of BiOCl 1−x I x structures was confirmed by analysis of XRD and Raman spectroscopy, and it was conserved throughout the entire range. XRD peak positions shifted in correlation with iodine content, which is discussed in relation to compositional analysis by XPS and EDS. The evaluation of photocatalytic activity, through degradation of methyl orange dye, showed that iodine-rich BiOCl 1−x I x structures are the most suitable for photocatalytic processes using both visible and UV light. EDTA scavenger tests showed that the photocatalytic process is dominated by holes (h+), and hydroxyl radicals (·OH).