Photocatalytic Decolorization of Methyl Red on Nanoporous Anodic ZrO2 of Different Crystal Structures

High surface area, self-organized nanoporous ZrO2 arrays with perfect adhesion to the Zr substrate were synthesized by anodization in an aqueous electrolyte containing (NH4)2SO4 and NH4F. The obtained semiconductor materials tested as photocatalysts for decolorization of methyl red (MR) a model azo dye pollutant. It was demonstrated that as-synthesized anodic layers are already crystalline and, therefore, do not require further thermal treatment provide high photocatalytic performance. However, efficiency could be improved annealing at relatively low-temperature 350 °C. Higher temperatures caused gradual drop activity. behavior correlated crystal phase transformation ZrO2. found higher activity observed tetragonal over monoclinic (predominant elevated temperatures). results from optimal complex electronic structure annealed three different energy states having absorption edges 2.0, 4.01 5.28 eV.