Preparation and investigation of structural and photocatalytic properties of phosphate modified titanium dioxide

A series of high surface area titanium dioxide samples (P-TiO2) with varying phosphate content have been prepared by the sol–gel technique. The structural characterization of the samples included X-ray powder diffraction, diffuse reflectance infrared and UV–vis spectroscopy (DRIFT and UV–vis–DR), and nitrogen adsorption measurements. The structural properties of the P-TiO2 samples significantly changed with the phosphate content and calcination temperature. According to XRD data the presence of phosphate shifts the anatase rutile phase transition to higher temperatures, revealing that phosphate improves the thermal stability of the samples. The specific surface area and the semiconductor band gap energy increase with the phosphate content.The photocatalytic activity of TiO2 and P-TiO2 was studied by phenol degradation in liquid phase. A small amount of phosphate of the catalysts increases the photocatalytic activity, but further increase of the P/Ti molar ratio (above 0.01), leads to a considerable loss in activity. The optimal calcination temperature of P-TiO2 was 300–500 °C. The phenol conversion rate is highest with catalysts calcined at 700 °C, but phenol does not degrade to carbon dioxide.