Addition of SnO₂ over an oxygen deficient zirconium oxide (Zr_xO_y) and its catalytic evaluation for the photodegradation of phenol in water

The ZrSn composites materials were prepared in one pot by chemical co-precipitation method. SnO₂ was incorporated to Zr_xO_y modifying the molar percentage from 1 to 5 mol%. The ZrSn composites were characterized by different techniques: XRD, FTIR, DRS, SEM, N₂ physisorption and HR-TEM. The ZrSn composites were dried at 80 °C and thereafter were evaluated in the photodegradation of phenol under UV irradiation. The percentages of degradation and mineralization were determined after a reaction time of 150 min by UV–Vis spectroscopy and Total Organic Carbon analysis (TOC), respectively. The composite containing SnO₂ in a 3 mol% showed the highest photoactivity with a 72% of photodegradation, a higher value compared with the obtained with TiO₂-P25 (62%). Finally, a possible reaction mechanism was proposed based on certain studies, which allows to follow the formation of the active species •OH, •O2⁻ and h⁺. The formation of the •OH specie was measured by fluorescence spectroscopy whereas the inhibition of the species •O₂⁻ and h⁺ was determined by UV–Vis spectroscopy. The results showed that the ZrSn composites not promotes the hydroxyl radical formation. In addition, the holes capture showed a full-loss of the photoactivity while the minimization of (•O₂⁻) radicals in the reaction media results in a decrement of the photoactivity. The formation of heterojunctions and the presence of localized states in the synthesized composites offer an excellent alternative for a fast photodegradation of phenol.