acid, or platinum in the photocatalytic oxidation of NO (50 ppm) with a flowing 7% O2 + N2 mixture under UV
irradiation in a flow reactor at room temperature and atmospheric pressure is reported. Because of the progres-
sive blocking of active sites of the photocatalyst by the reaction products (NO2,
), it is impossible to realize prolonged continuous removal of NOx (NO + NO2) from air without catalyst regeneration at elevated tempera-
tures. The efficiency of the photocatalysts is characterized by specific photoadsorption capacity (SPC) calcu-
lated from the total amount of NOx adsorbed during 2-h-long irradiation. Modification of TiO2 with 5% BaO or
5% urea raises the SPC of the catalyst by a factor of 2–3. Presumably, this promoting effect is due to the basic
properties of these dopants, which readily sorb NO2 and
. A considerable favorable effect on SPC is also attained by adding 0.5% Pt to (5% BaO)/TiO2. The SPC of the (0.5% Pt)/TiO2 catalyst depends on the state of
the platinum. The samples calcined in air at 500
C, which contain Pt+ and Pt2+, have an approximately 2 times higher SPC than unpromoted TiO2 and ensure a much larger NO2/NO ratio at the reactor outlet. Conversely, the
samples reduced in an H2 atmosphere at 200
C, whose platinum is in the Pt0 state, show a lower SPC than the initial TiO2 and cause no significant change in the NO2/NO ratio.