Improved photocatalytic degradation rates of phenol achieved using novel porous ZrO2-doped TiO2 nanoparticulate powders

Highlights: → Synthesis of TiO2 doped with ZrO2. → Decomposition of phenol from water. → Incorporation of ZrO2 strengthens material and increasing surface area. → ZrO2 also slows down the electron-hole pair recombination. → Regeneration was achieved with little adverse effect on the material. - Abstract: This paper studies the photocatalytic degradation of phenol using zirconia-doped TiO2 nanoparticles. ZrO2 was chosen due to its promising results during preliminary studies. Particles smaller than 10 nm were synthesised and doped with quantities of ZrO2 ranging from 0.5 to 4% (molar metal content). Particles were calcined at different temperatures to alter the TiO2 structure, from anatase to rutile, in order to provide an ideal ratio of the two phases. Powder X-ray diffraction (PXRD) analysis was used to examine the transformation between anatase and rutile. Degradation of phenol was carried out using a 40 W UV bulb at 365 nm and results were measured by UV-vis spectrometry. TEM images were obtained and show the particles exhibit a highly ordered structure. TiO2 doped with 1% ZrO2 (molar metal content) calcined at 700 oC proved to be the most efficient catalyst. This is due to an ideal anatase:rutlie ratio of 80:20, a large surface area and the existence of stable electron-hole pairs. ZrO2 doping above the optimum loading acted as an electron-hole recombination centre for electron-hole pairs and reduced photocatalytic degradation. Synthesised photocatalysts compared favourably to the commercially available photocatalyst P25. The materials also demonstrated the ability to be recycled with similar results to those achieved on fresh material after 5 uses.