Abstract
Use of silicon dioxide (SiO2) and titanium dioxide (TiO2) have been widely investigated individually in coatings technology, but their combined properties promote compatibility for different innovative applications. For example, the photocatalytic properties of TiO2 coatings, when exposed to UV light, have interesting environmental applications, such as air purification, self-cleaning and antibacterial properties. However, as reported in different pilot projects, serious durability problems, associated with the adhesion between the substrate and TiO2, have been evidenced. Thus, the aim of this work is to synthesize SiO2 together with TiO2 to increase the durability of the photocatalytic coating without affecting its photocatalytic potential. Therefore, synthesis using sonochemistry, synthesis without sonochemistry, physical characterization, photocatalytic evaluation, and durability of the SiO2, SiO2@TiO2 and TiO2 coatings are presented. Results indicate that using SiO2 improved the durability of the TiO2 coating without affecting its photocatalytic properties. Thus, this novel SiO2@TiO2 coating shows potential for developing long-lasting, self-cleaning and air-purifying construction materials.
Highlights
Current environmental problems observed in big cities, such as air pollution and associated infrastructure deterioration, encourage research for the development of new technologies and products that mitigate these modern, urban threats
Recent applications of photocatalytic building materials in urban pilot projects have demonstrated that maintaining the durability of the air-purifying and self-cleaning properties remains challenging, Coatings 2018, 8, 120; doi:10.3390/coatings8040120
It was observed that the morphology of the SiO2 @TiO2 coating was not affected by the use of sonochemistry
Summary
Current environmental problems observed in big cities, such as air pollution and associated infrastructure deterioration, encourage research for the development of new technologies and products that mitigate these modern, urban threats. Among the different environmentally-friendly technologies, heterogeneous photocatalytic oxidation using TiO2 has become an interesting technology due to its durability and high photocatalytic activity [1]. The incorporation of TiO2 (e.g., coatings or additives) into construction materials used in urban infrastructure, such as concrete and mortars, has been an interesting approach to reduce NOx and VOCs (volatile organic compounds) at outdoor concentrations using sunlight as the only energy source; these are the so-called air purifying properties. TiO2 under UV-A light irradiation can generate oxidative (·OH) and reductive (·O2 ) species, which are able to degrade different organic and inorganic compounds [2,3,4]. Recent applications of photocatalytic building materials in urban pilot projects have demonstrated that maintaining the durability of the air-purifying and self-cleaning properties remains challenging, Coatings 2018, 8, 120; doi:10.3390/coatings8040120 www.mdpi.com/journal/coatings
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