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 °C to 1000 °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 °C to 1000 °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 °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.