LUB0068A Abstract

In Texas and many parts of the USA, NO_x 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 proposed photocatalytic coating has potential to economically reduce nitrogen oxides (NOx) emissions and to directly decompose ozone 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 Texas ozone-non-attainment areas.

The Lamar portion of the proposal will address the synthesis of high activity, visible-light photocatalyst and the application of the advanced composite materials on concrete pavements. In order to tailor the photocatalysis to a specific application, whether it is NOx/VOC oxidation, NO/O₃ decomposition, or CO₂/metal reduction, it is important to tune the conduction and valence band levels to implement the required redox reactions and to harvest the maximum amount of light energy. The newly developed visible-light photocatalysts such as N-doped TiO₂ (TiO_xN_y) and exfoliated TiO₂-pillared MoS₂ typically have a smaller bandgap (~2.4 eV) and an absorption edge shifted to a lower energy region (365-550 nm). Exfoliated, pillared crystalline structures also offer a high surface area and activity. Further, photocatalysts can be enhanced with ferroelectric optical crystals (BaTiO₃ & LiNbO₃) via increased transmission/ scattering and electron-hole pair stabilization.

The objectives of this proposal are 1) to synthesize (or purchase) photocatalysts with doping and/or exfoliation techniques to realize both high surface area and high light harvesting.; 2) to modify the photocatalysts modified with ferroelectric optical crystal additives; 3) to test the photocatalytic activity on concrete slab and paint for NO oxidation and O₃ decomposition The photocatalytic materials will be furnished to the University of Houston for fabricating green construction materials and testing the products.

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. The requested funding from TARC is $40,000 for the first year. This project will be cost-shared with on-going HARC/EPA project in photocatalytic coating on urban surfaces, SAWC/USDA project on atrazine treatment & analysis, and other potential TxDOT/USEPA/USDOE projects.