Photocatalytic degradation and properties of core-shell like composite In2O3@Ba2In2O5 synthesized via chemical impregnation

A core-shell like composite In2O3@Ba2In2O5 was synthesized via a novel chemical impregnation method with sample calcination temperatures varying from 600 degrees C to 1000 degrees C. Crystal structure, phase transformation,and surface morphology due to heat treatment were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM), respectively. Additionally, in order to test the photocatalytic activity of the composite, the samples were added to a methylene blue (MB) solution, exposed to visible light, and then characterized by UV-vis diffused reflectance spectroscopy. Based on the XRD patterns, it could be determined that as calcination temperature was increased from 600 degrees C to 1000 degrees C, the outer shell of the composite transformed from Ba4In6O13 to Ba2In2O5 and from Ba2In2O5 to BaIn2O4. The composite sample synthesized with a Ba/In mole ratio of 0.9 and a calcination temperature of 800 degrees C demonstrated the best photocatalytic degradation activity out of all composite samples calcined at various temperatures. It degraded 100% of the MB in 30 min compared with commercial TiO2 (P-25), which degraded 100% of the MB in 120 min. It is hypothesized that the reason the core-shell like composite experiences superior photocatalytic degradation activity is due to the difference in the composite's energy bands, which drives electron-hole separation when light hits the core-shell like composite. (C) 2008 Elsevier B.V. All rights reserved.