Photocatalytic properties of Zirconium oxide – Impact of the calcination temperature

SSCI-VIDE+CARE+CGU:FDA:GBEInternational audienceThe interest of ZrO2 as semiconductor for photocatalytic applications has increased because of its non-toxicity, chemical stability, low cost and environmental friendliness. Zirconia is a wide band-gap oxide with an Eg value of about 5 eV. Therefore, controlling its defect profile in order to induce energy states in the band gap is the only possibility to make it a photocatalyst active.In our work, ZrO2 photocatalysts were prepared using a ‘one-pot’ sol-gel method followed by drying under supercritical conditions of solvent and calcination at temperatures varying between 400°C and 800°C. Samples were characterized by means of nitrogen adsorption-desorption isotherms at 77K, X-Ray Diffraction (XRD), Thermal analysis (TG), Raman spectroscopy, (High Resolution) Transmission Electron Microscopy (HR)TEM, Diffuse Reflectance Spectroscopy (DRS), Photoluminescence spectroscopy (PL) and X-ray photoelectron spectroscopy (XPS). Results emphasize that the aerogel preparation allows the creation of lower band gap states making it active under UV irradiation. The photoactivity of ZrO2 samples for the formic acid degradation follow the order; ZrO2 400 > ZrO2 800 > ZrO2 700 > ZrO2 500 > ZrO2 600. This activity order depends on the surface area, the nature of the ZrO2 phase (tetragonal or monoclinic) and the tendency to lattice distortion for high temperature treated samples. In this respect, ZrO2 800, even if calcined at high temperature, presents the highest surface density of structural defects compensating the low surface area (21 m2/g). This aerogel method of preparation therefore allows obtaining highly active zirconia photocatalytic samples in a wide range of thermal post-treatment