| Summary: | TiO<sub>2</sub> prepared by a green aqueous sol–gel peptization process is co-doped with nitrogen and zirconium to improve and extend its photoactivity to the visible region. Two nitrogen precursors are used: urea and triethylamine; zirconium (IV) tert-butoxide is added as a source of zirconia. The N/Ti molar ratio is fixed regardless of the chosen nitrogen precursor while the quantity of zirconia is set to 0.7, 1.4, 2, or 2.8 mol%. The performance and physico-chemical properties of these materials are compared with the commercial Evonik P25 photocatalyst. For all doped and co-doped samples, TiO<sub>2</sub> nanoparticles of 4 to 8 nm of size are formed of anatase-brookite phases, with a specific surface area between 125 and 280 m<sup>2</sup> g<sup>−1</sup> vs. 50 m<sup>2</sup> g<sup>−1</sup> for the commercial P25 photocatalyst. X-ray photoelectron (XPS) measurements show that nitrogen is incorporated into the TiO<sub>2</sub> materials through Ti-O-N bonds allowing light absorption in the visible region. The XPS spectra of the Zr-(co)doped powders show the presence of TiO<sub>2</sub>-ZrO<sub>2</sub> mixed oxide materials. Under visible light, the best co-doped sample gives a degradation of <i>p</i>-nitrophenol (PNP) equal to 70% instead of 25% with pure TiO<sub>2</sub> and 10% with P25 under the same conditions. Similarly, the photocatalytic activity improved under UV/visible reaching 95% with the best sample compared to 50% with pure TiO<sub>2</sub>. This study suggests that N/Zr co-doped TiO<sub>2</sub> nanoparticles can be produced in a safe and energy-efficient way while being markedly more active than state-of-the-art photocatalytic materials under visible light.
|
|---|
