Photocatalytic activity of nanocrystalline Fe3+-doped anatase TiO2 hollow spheres in a methylene blue solution under visible-light irradiation

Fe3+-doped anatase TiO2 hollow spheres (Fe:THs) were prepared using carbon sphere templates. The effects of Fe content on the microstructure, morphology, optical, and electrical properties as well as photocatalytic activity were studied. The crystallinity and crystal sizes of the Fe:THs samples decreased with increasing Fe dopant levels. The defect states of Fe4+, Fe3+, Fe2+, and oxygen vacancies that appeared in the lattice structure directly affect the optical behavior, electrical conductivity, and photocatalytic activity of Fe:THs. The hollow spheres with an Fe doping level of 0.25 mol% exhibited a maximum photodegradation efficiency of 91.93% under visible-light irradiation. This was attributed to the large surface area and high pore volume, which facilitated the permeation of synthetic dye into the hollow structure. The proper energy band gap, 3.19 eV and better electrical conductivity were the key factors affecting the reduced recombination rate of electron-hole pairs, leading to improved photocatalytic activity of the sample.