Thermostability and photocatalytic performance of BiOCl0.5Br0.5 composite microspheres

Novel 1-1.5 mu m BiOCl0.5Br0.5 composite microspheres were prepared by coprecipitation method, then calcined at different temperatures. The BiOCl0.5Br0.5 samples before and after calcination were characterized by powder x-ray diffraction, thermogravimetric analysis, N-2-physical adsorption, scanning electron microscopy, Fourier transformed infrared spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activity of the samples was evaluated by photocatalytic degradation of Rhodamine B under visible light irradiation. The results showed that the thermostability of BiOCl0.5Br0.5 composite microspheres is lower than BiOCl and higher than BiOBr. Heat treatment at low 500 degrees C could obviously improve the crystallinity of BiOCl0.5Br0.5 microspheres, resulting in a significant increase in activity. BiOCl0.5Br0.5 microspheres calcined at 450 degrees C displayed the highest activity and stability. At elevated temperature calcination (600-800 degrees C), phase transition occurred over BiOCl0.5Br0.5. Br element was gradually lost and new phase of Bi24O31Br10 appeared. High temperature calcination did not change the morphology of BiOCl0.5Br0.5, but the surface area and surface OH groups decreased, which resulted in a large decrease in activity.