Influence of Ultraviolet Light on Photocatalytic ${\mathsf{TiO}}_{\mathsf{2}}$ Materials

${\mathrm{NO}}_{\mathrm{x}}$ gases affect the diurnal rise and fall of tropospheric ozone. By removing ${\mathrm{NO}}_{\mathrm{x}}$ gases through the use of titanium dioxide (${\mathrm{TiO}}_2$) photocatalytic materials, tropospheric ozone concentrations could be reduced. Recent developments related to the photocatalytic pollution reduction capabilities of ${\mathrm{TiO}}_2$ have led a movement to understand the material properties required to create construction materials which have the potential to reduce ${\mathrm{NO}}_{\mathrm{x}}$ air pollutants. A research program was undertaken to isolate variables that impact the kinetics of ${\mathrm{TiO}}_2$ reaction. Six ${\mathrm{TiO}}_2$ materials were tested for ${\mathrm{NO}}_{\mathrm{x}}$ removal efficiencies. The productive ${\mathrm{TiO}}_2$ materials were then tested at multiple concentrations to determine the effect of ultraviolet (UV) irradiance on their efficiency to reduce ${\mathrm{NO}}_{\mathrm{x}}$ air pollutants. It was found that specific anatase ${\mathrm{TiO}}_2$ phases manufactured and sized to have high levels of photocatalytic activity could reduce ${\mathrm{NO}}_{\mathrm{x}}$ air pollutants at high efficiencies. The ${\mathrm{NO}}_{\mathrm{x}}$ removal efficiency was 2.4 times higher at a UV irradiance of $1,300\mathrm{\mu W}/{\mathrm{cm}}^2$ than at $150\mathrm{\mu W}/{\mathrm{cm}}^2$, equivalent to a sunny or shady surface, respectively.