In USA and many parts of the world, NOx emissions have become a constraint for sustainable economic development due to ozone non-attainment. Under light illumination over a photocatalyst free radicals are generated to oxidize or decompose pollutants. In air pollution control, NOx are oxidized to nitric acid while volatile organic compounds (VOCs) are oxidized to water, CO2, and chloride. Ozone can be decomposed to oxygen over photocatalysts. Recent developments in Europe, Japan, and US have demonstrated the interest in deploying photocatalytic technologies in environmental remediation. The photocatalytic coating has potential to economically reduce nitrogen oxides (NOx) emissions at ambient conditions nearly maintenance-free. NOx will be oxidized to nitric acid, neutralized by the alkaline base materials in concrete, and washed away by rain. The reduction on the number of high ozone days can be significant to allow sustainable economic developments in the many ozone-non-attainment areas worldwide.

We report the application of photocatalytic coating on concrete pavements to harvest the light energy for NOx pollution control. One of the focuses will be pavement coated visible-light photocatalysts such as N-doped TiO2 (TiOxNy). Further, photocatalysts can be enhanced with ferroelectric optical crystals (BaTiO3 & LiNbO3) via increased transmission/ scattering and electron-hole pair stabilization. The developed technology can be transferred to the cement and coating industries to meet the tighter emission standards and will give architects and town planners a new weapon in the fight against pollution in the foreseeable future.

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