Photocatalyst (0.2 g) was coated
onto a dish with a diameter of 12.0 cm. The coated dish was
then pretreated at 70 °C to remove water in the suspension.
The NO gas was acquired from compressed gas cylinder at
a concentration of 48 ppm NO (N2 balance, BOC gas) with
traceable National Institute of Stands and Technology (NIST)
standard. The initial concentration of NO was diluted to about
400 ppb by the air stream supplied by a zero air generator
(Thermo Environmental Inc. model 111). The desired humidity
level of the NO flow was controlled at 70% (2100 ppmv)
by passing the zero air streams through a humidification
chamber. The gas streams were premixed completely by a
gas blender and the flow rate was controlled at 4 L.min-1 by
a mass flow controller. After the adsorption-desorption
equilibrium among water vapor, gases and photocatalysts
was achieved, the lamp was turned on. The concentration
of NO was continuously measured by a chemiluminescence
NO analyzer (Thermo Environmental Instruments Inc. model
4