Synthesis and characterization of phosphor and nitrogen co-doped titania

Phosphor and nitrogen co-doped titania were prepared by a simple modified sol–gel method with hypophosphorous acid and ammonia as the P and N sources, respectively. The resulting materials were characterized by X-ray diffraction (XRD), nitrogen physical adsorption at 77 K, Fourier transformed infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and UV–vis spectroscopy. It was found that modification by phosphor could retard the phase transformation of anatase to rutile and increase the surface area significantly, while the doped nitrogen had little influence on the thermal stability and texture of the titania. The chemical nature of N and P was identified by XPS as NTiO and TiOP in the anatase TiO2 lattice. UV–vis spectra showed that modification by phosphor or nitrogen extended the spectral response of titania into the visible region. The photocatalytic activity of titania modified by only nitrogen was limited, much lower than that of phosphor-doped titania. However, when titania was co-doped with both phosphor and nitrogen, the photocatalytic activity was further enhanced efficiently.