Smart Surfaces: Heterogeneous Photo-Catalysis on TiO 2 Based Coatings for De-pollution Purposes in Indoor and Outdoor En
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ORIGINAL PAPER
Smart Surfaces: Heterogeneous Photo‑Catalysis on TiO2 Based Coatings for De‑pollution Purposes in Indoor and Outdoor Environments Dimitrios Kotzias1,4 · Vassilios Binas2,3 · George Kiriakidis2,3
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Heterogeneous photocatalysis using semiconductors, e.g. T iO2 as photocatalyst is a promising technology for the degradation of environmental pollutants. Preliminary evidence indicates that T iO2 containing construction materials and paints efficiently destroy the ozone precursors NO and N O2 up to 80% and 30% respectively. The materials and paints containing T iO2 developed so far are mostly for outdoor use. In the last decades, substantial efforts made to investigate further the photocatalytic activity of materials containing TiO2 towards priority air pollutants like NO, NO2, and volatile organic compounds (VOCs) frequently accumulated in indoor environments. A particular asset of these studies was to modify the titanium dioxide (TiO2) in such a way that it can be activated by visible light to use in building materials and paints used indoors, too. Keywords Photocatalysis · TiO2 · NOx · VOC
1 Introduction In the last decades heterogeneous photocatalysis using semiconductor oxides e.g. T iO2 as photocatalyst found great attention [1, 2]. Light excitation of TiO2 (3.2 eV energy gap), with wavelengths between 360 and 380 nm (UV-light), generates electrons and positive holes in the conduction and valence bands, respectively. These species are very reactive and can either recombine very fast (within femtoseconds) or diffuse to
Presented at the World Chemistry Forum, May 22–24, 2019, Barcelona/Spain. * Dimitrios Kotzias [email protected] 1
Form.Sen. Official, EC‑Joint Research Centre, Institute for Health and Consumer Protection, 21027 Ispra, VA, Italy
2
Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, P.O. Box 1527, 71110 Heraklion, Greece
3
Department of Physics, Crete Center for Quantum Complexity and Nanotechnology, University of Crete, P.O. Box 2208, 71003 Heraklion, Greece
4
Present Address: Bonn, Germany
semiconductor surface where they are trapped by adsorbed molecules of e.g. water and oxygen (Fig. 1). They initiate the formation of hydroxyl radicals and other reactive species that can attack pollutant molecules e.g. NOx, volatile organic compounds (VOCs) and thus degrade them. NOx gases, known as atmospheric ozone precursors, are oxidized to nitrates using T iO2-modified materials activated by UV-light. Similar processes were investigated for VOCs leading to the degradation of priority pollutants e.g. toluene. Hence, building materials modified/enriched with TiO2 gained an increasing importance, given the full range of possible applications [3–7]. TiO2-based photocatalytic materials are initially developed and used as outer coatings in the facades of buildings to clean the air along the roadways that is polluted by automobile exhaust gase
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