Long term self-cleaning and photocatalytic performance of anatase added mortars exposed to the urban environment

TiO2 alterations with natural aging: Unveiling the role of nitric acid on NIR reflectance

“…Outdoor exposure campaigns were first carried out on commercial materials: fiber-reinforced mortars [27] and bituminous roofing membranes coated with siloxane paint, both exposed in triplicate and both in a standard formulation and in a photoactive one, the latter containing anatase TiO2. The reflectance of samples with standard composition decreased, especially in the wavelength range between 400 and 2200 nm, consistently with previous work [29,35], due to the complex of UV aging, soot and other particulate deposition ( Figure S1, Supporting Information).…”

“…One focused on uncoated commercial fiber-reinforced mortars, containing TiO2 in mass in the mortar formulation, constituting the outer skin of pre-cast thermally insulated panels produced by PIZ SpA [25,27]. The mortar formulation, with special reference to the type and content of photocatalytic admixture, was previously optimized [28]; composition is reported in Table 1.…”

Self-cleaning building materials: The multifaceted effects of titanium dioxide

“…Then, the full characterization was performed on complete samples (paint, sand, and NPs). To check photocatalytic activity, rhodamine Ban azo dye with magenta huewas chosen, as it is commonly accepted and utilized to test the efficiency of photocatalytic materials as representative of organic pollutants, as attested by several independent research groups [14,29,31,[47][48][49][50].…”

“…While the mechanisms of photocatalytic and self-cleaning activity have been long studied, together with the development of materials with improved photoactivated performance, their durability and the appraisal of the photoactivated effects over time, in real working conditions, remain only marginally treated. This is particularly true in the case of building materials used outdoors, where environmental agents such as rain, wind, pollution and microbiological growth may gradually deactivate the TiO2 component, or cause the degradation of the whole material by erosion or other physical mechanisms [11,12,[29][30][31][32].…”

“…We recently demonstrated that anatase added materials suffer a less pronounced drop in solar reflectance upon environmental exposure (0.19 instead of 0.26, after two years) [35]. In the second portion of the near-infrared wavelength range, namely between 1500 nm and 2500 nm, as aging proceeds, the reflectance increases even in comparison to the freshly prepared material, which was ascribed to the material photocatalytic NOx degradation, responsible for the formation of nitric acid that alters the optical properties of the TiO2 nanoparticles (NPs) present in the material [29,35].…”