Hollow β-Bi2O3@CeO2 heterostructure microsphere with controllable crystal phase for efficient photocatalysis

Herein, a two-step hydrothermal synthesis is used to successfully prepare a Bi2O3 microsphere coated with CeO2 nanosheets on the surface. The resultant core/shell Bi2O3@CeO2 microsphere is calcined at different temperatures, yielding a series of Bi2O3@CeO2-t hollow microspheres. It is found that, with the increasing calcination temperature, the Kirkendall effect occurred can impel the interior Bi2O3 to gradually diffuse outward the Bi2O3@CeO2 microsphere, meanwhile the crystal structure of Bi2O3 transforms from the metastable tetragonal phase (β) to the stable monoclinic phase (α) at 350 °C. Phase-controllable preparation of the Bi2O3@CeO2-350 composite with the highly active β-Bi2O3 is pursued to obtain the high electron-transfer efficiency between β-Bi2O3 and CeO2, thus exhibiting superior photocatalytic performance in the photocatalytic degradation of tetracycline (TC) under visible light irradiation. Therefore, Kirkendall effect can be exploited as a new methodology to effectively improve the photocatalytic performance of heterojunction photocatalysts.