Indium oxide (InO) hollow microspheres were prepared using yeast as a bio-template with the aid of a precipitation method. The yeast provided a solid frame for the deposition of In(OH) to form the precursor. The resulting InO hollow microspheres were obtained by calcining the precursor at 650 °C. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N adsorption-desorption isotherms and UV-Vis diffuse reflectance spectroscopy. The results showed that the diameter of the InO hollow microspheres was about 2.0-3.0 μm and the spherical shells were composed of InO nanoparticles with a size of ∼20 nm. The BET specific surface area of the sample was 19.23 m g. The photoelectrocatalytic test results showed that the photoelectrocatalytic degradation efficiency of methylene blue (MB) using InO hollow microspheres as catalysts under visible light irradiation and a certain voltage could reach above 95% after 4 hours, much higher than that of only photodegradation. The enhanced photoelectrocatalytic activity could be attributed to the hydroxyl radicals HO˙ produced by the light irradiation reaction process which could oxidize the electron donors and were beneficial to reducing the recombination of electrons and holes.

The nanotubes with an anatase structure were hydrothermally synthesized using the Fe-doped anatase nanopowder precursors that were annealed in air and reductive atmospheres. The microstructure and physicochemical properties of the nanotubes were comparably investigated. Results show that the reductive pre-annealing yields more surface-chemisorbed oxygen by introducing lower valance Fe 2+ and Ti 3+ ions. The specific surface area, methylene blue adsorption and photoabsorption threshold of the nanotubes are greatly enhanced by the reductive annealing when comparing with annealing in air. 1 mol% Fe doping and reductive annealing yield the highest adsorption, photocatalytic efficiency and durability for degradation of MB solution; extreme Fe doping decreases the photocatalytic efficiency. The Fe content of the nanotubes is decreased by the hydrothermal synthesis, especially in the case of annealing in air. Moreover, the action mechanism of the Fe doping and reductive annealing was discussed.