Photocatalytic studies of Ho–Zr–O nano-composite with controllable composition and defects

With the help of sol–gel method assisted by melting salt, a series of Ho–Zr–O nano-composite with controllable composition and defects have been successfully prepared. Characterization results show that the positions, intensity, and width of the X-ray diffraction peaks of the products have a regular variation with the increase of zirconium element which implies the gradual changes of crystal spacing and product size. At the same time, the molar ratios between holmium and zirconium ions are consistent with the chemical formula and both of them are uniformly distributed in products further showing the perfect formation of targeted materials. Optical properties reveal that diversified defect forms of Ho–Zr–O nano-composite lead to the different absorptions of visible light. Photocatalytic experiments demonstrate Zr0.8Ho0.2O2 − δ nano-crystals have excellent visible-light-responsive photocatalytic activities on some familiar dyes (e.g.: methylene blue and Rhodamine B) which results from the special defect structure, better absorption of visible light and larger specific surface area. It follows that Zr0.8Ho0.2O2 − δ nano-crystals are a new kind of visible-light-responsive photocatalysts with better prospects in conversion and utilization of solar energy. Also, the present melting salt assisted route might be generalized to synthesize other AxByOz composite oxide nano-crystals with more complicated structures.