High photocatalytic activity of aerogel tetragonal and monoclinic ZrO2 samples

Abstract

ZrO2 nanoparticles have been investigated in the photodegradation of formic acid under UV irradiation. 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 adsorption-desorption isotherms, XRD, Thermal analysis, Raman spectroscopy, HRTEM, DRS, PL and XPS. The aerogel preparation allows the creation of intermediate band gap states making it active under UV irradiation. The photoactivity of ZrO2 samples follow the order; ZrO2 400 ≥ ZrO2 800 > ZrO2 700 > ZrO2 500 > ZrO2 600 in agreement with their optical properties. The lower the value of mid band gap, the higher the photocatalytic activity. The value of mid band gap depends on the nature of the ZrO2 phase (tetragonal or monoclinic), surface oxygen defects and the tendency to lattice distortion for samples treated at high temperature. This study therefore shows for the first time that adequate preparation of oxide materials (here ZrO2) allows finely tuning the creation of intermediary band gap sites through thermal post-treatments making ZrO2, a large band gap material, able to photocatalytically work under UV irradiation.