TiO2 is one of the most commonly used photocatalysts. In Hong Kong, a study titled "Ambient Air Treatment by Titanium Dioxide Based Photocatalyst" was conducted in 2002 (you can find the paper in the web). The purpose of the study was to determine the durability of TiO2 catalyst. Extensively used TiO2-coated paving blocks were tested for their use in the photocatalytic oxidation of NOx. (a) State the properties of TiO2 that are critical for its photocatalytic activity, showing the chemical equations for the generation of high oxidizing power hydroxyl radicals under UV radiation (wavelength