Dye-Sensitized Titanium Dioxide Photocatalysis – a Novel Solution for Personal Air Filtration

Abstract

Ambient air pollution is attributed to 4.2 million deaths annually and accounts for nearly 30% of the global top 6 leading causes of death. According to the World Health Organization, 99% of the world population lives in areas with dangerously high levels of pollutants, most being in low-income countries. Although current solutions exist, none are both cheap and efficient at filtering out Particulate Matter (PM) and Volatile Organic Compounds (VOCs) outdoors. Photocatalysis, a process known to occur in photovoltaic semiconductors, has proven to degrade pollutants, but only under Ultraviolet Light, which accounts for just 3-5% of sunlight. In this experiment, the dye-sensitization method was tested to increase the filtration efficiency of a semiconductor, Titanium Dioxide (TiO₂), under visible light. The dyes tested were Flavonoids, which are natural antioxidants found in fruits that have also been previously used to improve the efficiency of photovoltaic electricity production, from Blackberry, Blueberry, Raspberry and Parsley. Each filter was coated in a solution of Dye-sensitized TiO₂. The filters’ efficiencies were then evaluated by passing contaminated air through each filter into a testing chamber where the resulting quality of the air was analyzed with an air quality monitor. The Parsley-TiO₂ filter was the most efficient, removing nearly all VOCs, PM_2.5, PM₁₀ and PM₁, and the estimated cost to create the filter was approximately $2. This filter could save millions of lives, due to its low cost of production, and could potentially be applied in impoverished areas of polluted cities like Beijing and New Delhi.