Photocatalytic properties of phosphor-doped titania nanoparticles

Phosphor-doped titania nanoparticles in an anatase phase were prepared by a simple modified sol–gel method with hypophosphorous acid as a precursor. The resulting materials were characterized by differential thermal analysis-thermogravimetry (DTA-TG), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), nitrogen physical adsorption at 77 K, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), FT-IR pyridine adsorption spectroscopy, and UV–vis spectroscopy. It was found that the phosphor-doped species could significantly increase the surface area of the materials, and consequently gave them a higher content of surface hydroxyl groups. Moreover, the phosphor-doping improved the thermal stability of titania and decreased the phase transformation of anatase to rutile to a certain extent. UV–vis spectra proved that the modification by phosphor shifted the absorption edge of titania to the visible region, making it an effective photocatalyst in visible light. This was demonstrated by the degradation of MB and 4CP under visible-light (>400 nm) irradiation. The excellent photocatalytic activity of phosphor-doped titania compared with pure titania could be explained by its high surface area and small crystallite size.