Influence of Fe3+ and Ho3+ co-doping on the photocatalytic activity of TiO2

The un-doping, single-doping and co-doping TiO2 nanoparticles have been prepared by sol–gel method with Ti(OC4H9)4 as a raw material and characterized by X-ray diffraction (XRD) and UV–vis absorption spectra, and their photocatalytic activities have been investigated by photocatalytic oxidation of methyl orange. It is found that Fe3+-doping broadens the absorption profile, improves photoutilization of TiO2, and then generates more electron–hole pairs. Ho3+-doping restrains the increase of grain size, leads to crystal expansion and matrix distortion and retards the recombination of the photoexcited charge carriers. The photocatalytic activity of TiO2 co-doped with Fe3+ and Ho3+ ions is markedly improved due to the cooperative actions of the two dopants.