Hollow Spherical Hierarchical MoO₃/SiO₂–TiO₂ Structures for Photocatalytic Decomposition of Organic Pollutant in Water

In this study MoO₃/TiO₂–SiO₂ layered spherical composites, having hierarchical structure, were synthesized on TOKEM-320Y anion exchanger template using by sol-gel methods. Properties of MoO₃/TiO₂–SiO₂ composites were characterized by XRD, EDS, SEM, 3D X-ray microtomography, Raman, IR, DRS, BET, and PL techniques. The SEM, 3D X-ray microtomography and EDS analysis showed hollow spherical composites with diameters ranging from 200 to 400 μm with core/shell structure. The formation of TiO₂–SiO₂ shell on the MoO₃ core results in lower oxygen vacancy concentrations in composite (0.0425) and a reduced bandgap width (2.56 eV in compare to 3.19 eV for MoO₃ sample, which was analyzed through the UV–VIS DRS method). The performance of MoO₃/TiO₂–SiO₂ composites was evaluated by photocatalytic degradation of methylene blue (MB) aqueous solution irradiated with an I₂ excilamp (λ_max = 312 nm). The photoabsorption energy properties of MoO₃/TiO₂–SiO₂ composites are related to the interaction between TiO₂–SiO₂ and MoO₃ which occurs through oxygen in Ti-O-Mo and Si-O-Mo. The MoO₃/TiO₂–SiO₂ composites exhibited a much higher photocatalytic activity (rate constant is 0.0645 min^‒1, degradation efficiency is 93% (20 min). This work demonstrates the relation between the formation of heterostructure in core/shell composite and its photocatalitic activity, providing fundamental guidance to improve photocatalytic performance of materials.