TiO2–ZnO Composite Sphere Decorated with ZnO Clusters for Effective Charge Isolation in Photocatalysis

Abstract

TiO2 and ZnO are extensively used photocatalysts, but their activity needs improvement due to rapid charge recombination. Herein, we designed and synthesized a novel structure of a TiO2–ZnO composite sphere decorated with ZnO clusters by a one-pot solvethermal method. TEM and EDX characterizations show this structure contains a TiO2 core, TiO2–ZnO composite (type II heterojunction) surface layer, and surface c-axis ZnO clusters. The in situ Au and PbO2 photodeposition shows that the photoinduced electrons and holes are driven to ZnO clusters and TiO2, respectively, attributed to the synergy of the type II heterojunction of TiO2–ZnO and high electron mobility of ZnO. The PL spectra confirm that such a structure is much more efficient in retarding the charge recombination than the sole TiO2–ZnO sphere. Importantly, this structure shows higher photoactivity in degradation of rhodamine B and isomerization of norbornadiene than pure TiO2, ZnO, and TiO2–ZnO composite spheres.