Temperature effect on phase transition and morphological transformation of BiOI microspheres to Bi5O7I microstructures

Abstract In this work, three-dimensional Bi5O7I microstructures were successfully fabricated by a thermal conversion of BiOI microspheres in air at temperatures ranging from 450 to 525 °C. The phase structure, morphology, and optical property of the Bi5O7I powders were characterized with respect to that of parent BiOI by XRD, SEM, XPS, TEM, and UV–vis spectroscopy, respectively. The results revealed that porous BiOI microspheres were completely transformed to porous Bi5O7I microstructures at 450 °C. The surface morphology of BiOI microspheres was gradually changed from ultrathin nanosheets to large 3D crystals of Bi5O7I by increasing the heat treatment temperature. The photocatalytic activity of the Bi5O7I powders fabricated at different heat treatment temperatures was investigated by the degradation of Rhodamine B in aqueous solution. Among the samples, the sample heat treated at 450 °C showed the highest photocatalytic activity due to its high crystalline, high surface area and porous microstructures.