A Photocatalytic Building Façade for Improving Urban Air Quality

Fossil fuel combustion generates various types of air pollutants. Nitrogen dioxide (NO2) is the primary source of air pollution in populated urban areas, especially in developing countries. This study investigates an air pollutant reduction system that utilizes a photocatalytic substance on building facades. Titanium Dioxide (TiO2), one of the most effective photo-induced catalysts, can be excited by UV-A rays with a wavelength shorter than 385nm. Excited TiO2 can then break water vapor molecules in the air to form hydroxyl radicals. Due to its strong oxidation properties, hydroxyl radicals can subsequently react with air pollutants and form harmless substances, e.g., turning NO2 into nitrates. In this study, we conducted experiments to test the effects of photocatalytic facades reducing air pollutants under UV rays. We fabricated a small scale (30cm x 30cm) building façade model and coated it with a thin layer of titanium dioxide. The model is then put into an airtight chamber filled with exhaust gas from an internal combustion engine. Inside the chamber, we installed a set of environmental sensors that measure NO2, UV intensity, temperature, and relative humidity. The sensors were connected to a Raspberry Pi that is used to collect the sensor data. Natural sunlight was used as the UV source to activate the TiO2 on the model. Under sunlight, the concentration of NO2 dropped noticeably over time. In a controlled experiment, on the other hand, the concentration of NO2 monotonically increased without the UV rays. This study shows that photocatalytic facades with titanium dioxide coating can reduce urban air pollutants through photocatalysis. In urban areas with severe air pollution and a large amount of building surface area, photocatalytic facades can be an effective passive system to improve urban air quality.

https://doi.org/10.35483/ACSA.AM.110.6

Volume Editors
Robert Gonzalez, Milton Curry & Monica Ponce de Leon

ISBN
978-1-944214-40-1