Facile preparation of spherical TiO2 inverse opals with enhanced visible-light photodegradation of methylene blue

In this work, the spherical TiO2 inverse opal photonic crystals (IOPCs) have been successfully prepared through the combination of sol–gel and liquid phase deposition (LPD) method using SiO2 spheres as the templates. The characterization results show that the spherical TiO2 inverse opal structure can significantly increase the specific surface area and total pore volume. The photocatalytic experiments reveal that the removal rate of Methylene blue (MB) by TiO2 with spherical inverse opal (IO) structure (TiO2-710) was 98% under illumination for 40 min, while the degradation rate of TiO2 without IO structure (TiO2-Sol) was only 17.7%. Moreover, the TiO2-710 sample exhibits the highest reaction rate constant, which is about 9.1 times that of TiO2-Sol. The enhancement of photocatalytic activity can be attributed to the existence of the unique spherical inverse opal structure.