Synthesis and photoelectrocatalytic activity of In₂O₃ hollow microspheres <i>via</i> a bio-template route using yeast templates

Abstract

Indium oxide (In₂O₃) 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)₃ to form the precursor. The resulting In₂O₃ 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), N₂ adsorption-desorption isotherms and UV-Vis diffuse reflectance spectroscopy. The results showed that the diameter of the In₂O₃ hollow microspheres was about 2.0-3.0 μm and the spherical shells were composed of In₂O₃ nanoparticles with a size of ∼20 nm. The BET specific surface area of the sample was 19.23 m² g^-1. The photoelectrocatalytic test results showed that the photoelectrocatalytic degradation efficiency of methylene blue (MB) using In₂O₃ 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.