Photocatalytic abatement of ambient NOx by TiO2 coated solar panels†

Abstract

Nitric oxide and nitrogen dioxide (combined, known as NO_x) and their contribution to ozone and photochemical smog generation are persistent issues in urban environments. Many technologies have been developed to alleviate this issue, including photochemical transformation. While previous experiments have focused on incorporating photocatalysts into paving and building materials, we report coating glass substrates for the eventual application to solar panels that are inherently positioned to optimize the amount of solar exposure they receive, creating a surface compatible with photocatalytic coatings. As most photocatalyst materials absorb the ultraviolet spectrum outside the light range used for energy production, this approach could enable dual-functionalized solar panels for energy generation and air remediation. Proof of concept testing was conducted to determine the effectiveness of TiO₂-based photocatalytic products to oxidize NO_x to NO₃⁻/HNO₃. It was found that the tested TiO₂-based photocatalytic products can successfully reduce NO_x concentrations by up to 36%. With the success of laboratory proof of concept experiments, field testing was conducted to determine if glass panels coated with TiO₂ products can reduce NO_x concentrations in environmental conditions. Deionized water washes of the coated glass panels were analyzed through ion chromatography to determine the concentration of NO₃⁻ formed on the surface of the coated glass panels. Field testing resulted in flux values up to 33 mg of NO₃⁻ per m² per day and an average flux up to 8.8 mg of NO₃⁻ per m² per day, representing an order of magnitude value to evaluate possible large-scale implementation. Utilizing field testing results, scale-up estimations suggest widespread application would have a limited impact on total NO_x concentrations. Still, at the local scale, deployment at sites with elevated NO_x concentrations could meaningfully improve local air quality.