Influence of Zr as TiO2 doping ion on photocatalytic degradation of 4-chlorophenol

Nanosized Zr-doped TiO2 photocatalysts were prepared using the homogenous co-precipitation method from aqueous solutions containing TiOSO4 and ZrCl4 by urea as a precipitation agent, with subsequently annealing at various temperatures of 400–1100 °C. Structural changes of the photocatalysts upon heating were studied by X-ray powder diffraction. Anatase-to-rutile phase transformation is shifted to higher temperatures in comparison with undoped TiO2. Spherical clusters morphology was revealed by scanning electron microscopy. Energy dispersive X-ray spectrometry confirmed a Zr content of 0.8 mol% in all samples. The band-gap energies were determined from diffuse reflectance UV–vis spectra. The spectral thresholds are shifted toward visible region, except for the unheated catalyst. X-ray photoelectron spectroscopy measurements revealed that the binding energy of Ti 2p3/2 electrons is not influenced by Zr doping. On the contrary, the binding energy of Zr 3d5/2 electrons is lower than that of Zr ions in ZrO2. Photocatalytic degradation of 4-chlorophenol was employed to test photoactivity of the catalyst. The photocatalyst annealed at 900 °C has a 1.5 times higher degradation rate than the standard TiO2 P25 (Degussa).