Hierarchical nanosheet-assembled yolk–shell TiO2 microspheres with improved photocatalytic activity

Abstract

Nanosheet-assembled yolk–shell anatase TiO₂ microspheres were synthesized utilizing the slow hydrolysis of K₂TiO(C₂O₄)₂ in a mixed solution of H₂O₂ and HNO₃. Under a temperature near to the ambient one, microspheres assembled with nanoparticles were firstly obtained at the early reaction stage. Prolonging the reaction duration led to the formation of urchin-like microspheres, which further developed into nanosheet-assembled yolk–shell microspheres through a dissolution–precipitation procedure. The intermediate acid washing and final calcination transformed the microspheres to phase-pure anatase TiO₂. The yolk–shell anatase microspheres exhibited a photocatalytic activity twice that of the urchin-like microspheres when utilized to assist the photodegradation of both rhodamine B and phenol in water under the illumination of UV light.