Efficiencies Evaluation of Photocatalytic Paints Under Indoor and Outdoor Air Conditions

Abstract

The removal of indoor and outdoor air pollutants is crucial to prevent environmental and health issues. Photocatalytic building materials are an energy-sustainable technology that can completely oxidize pollutants, improving in situ the air quality of contaminated sites. In this work, different photoactive TiO 2 catalysts (anatase or modified anatase) and amounts were used to formulate photocatalytic paints in replacement of the normally used TiO 2 (rutile) pigment. These paints were tested in two different experimental systems simulating indoor and outdoor environments. In one, indoor illumination conditions were used in the photoreactor for the oxidation of acetaldehyde achieving conversions between 37 and 55%. The other sets of experiments were performed under simulated outdoor radiation for the degradation of nitric oxide, resulting in conversions between 13 and 35%. This wide range of conversions made it difficult to directly compare the paints. Thus, absorption, photonic, and quantum efficiencies were calculated to account for the paints photocatalytic performance. It was found that the formulations containing carbon-doped TiO 2 presented the best efficiencies. The paint with the maximum amount of this photocatalyst showed the highest absorption and photonic efficiencies. On the other hand, the paint with the lowest amount of carbon-doped TiO 2 presented the highest value of quantum efficiency, thus becoming the optimal formulation in terms of energy use.

Using visible light to activate antiviral and antimicrobial properties of TiO2 nanoparticles in paints and coatings: focus on new developments for frequent-touch surfaces in hospitals

“…The outdoor experiments under UV light showed that the conversion ability of the different paints all decreased substantially with time, possibly due to oxidation products forming on the surfaces. 124 , 125 …”

“…The outdoor experiments under UV light showed that the conversion ability of the different paints all decreased substantially with time, possibly due to oxidation products forming on the surfaces. 124,125 Currently, most commercial self-cleaning window surface coatings can only be activated by UV light. Recently, Peeters et al manufactured a transparent photocatalytic self-cleaning Au/TiO 2 coating that is activated in normal light conditions.…”

“…They achieved a > 99.99% (> 4.17-log) reduction in viral activity after irradiation with a 15 W UVA lamp for 20 min. 127 Salvadores et al 124 used undoped and carbon-doped TiO 2 in different amounts in the formulation of waterbased and pseudo-paints and tested them for degradation of acetaldehyde under indoor conditions using visible light. They also evaluated the degradation of NOx under outdoor conditions using UV light.…”

Can photocatalysis help in the fight against COVID-19 pandemic?

“…showing that titanium(IV) oxide is active against gram-positive and gram-negative bacteria ( Lactobacillus acidophilus and Escherichia coli , respectively) and yeast Saccharomyces cerevisiae [ 20 ]. The main area of photocatalysis application is the preparation of self-cleaning surfaces (also for antifouling purposes) [ 21 , 22 , 23 , 24 , 25 ]. However, more and more interest has recently been focused on indoor air purification [ 26 ], water/wastewater treatment [ 27 ], fabrication of masks and clothes [ 28 ], and medical purposes (wound healing [ 29 , 30 ]).…”

Low temperature curable titanium-based sols for visible light photocatalytic coatings for glass and polymeric substrates

“…With the aim of developing titanium-based photoactive coatings under visible light, some research works have focused on reducing the band gap of these materials. Some of the strategies employed are based on doping titanium dioxide with other metals, such as silver, 10 aluminum, 11 tin, 12 iron and zinc, 13 or with non-metals, such as carbon, 14 nitrogen 15,16 and mixtures of silicon-nitrogen. 17 Some other research works have focused on developing photoactive coatings with low processing temperatures by doping amorphous titanium(IV) oxide with nickel and nitrogen.…”