Ozone formation from illuminated titanium dioxide surfaces.

The nitrogen oxides (NO(x)) decomposition on illuminated TiO(2) surfaces has been widely studied, but little is known about the subsequent formation of non-nitrogen containing products. In this study, TiO(2) coated glass surfaces and TiO(2) films with nitrate anions (either premixed with TiO(2) as KNO(3) or deposited from gaseous NO(x)) are irradiated with broad-band light. Upon irradiation, detected gas phase products include NO(2), HNO(2), and O(3). To the best of our knowledge, this is the first study that reveals the production of O(3) from TiO(2) surfaces. By surface charge transfer reactions, nitrate anions are oxidized into nitrate radicals and their photochemistry (almost in the visible) leads to O(3) formation, enhancing the oxidizing power of these surfaces.