Humidity and temperature influence on the self-cleaning performance of building materials containing the photocatalysts

Titanium dioxide is a well-known substance for its photocatalytic properties.The aim of this article is to describe the influence of humidity and temperature on the self-cleaning properties of construction surfaces covered with a layer of titanium dioxide (further labeled as TiO2).Its bandgap allows for the use of its photocatalytic properties strictly when exposed to the UV irradiation.The physico-chemical characteristics of the used TiO2 were investigated and described using analytical methods: x-ray diffraction spectroscopy (XRD), diffuse reflectance spectroscopy (DRS) and scanning electron microscopy (SEM).The experiments carried out aimed to identify the effect of humidity and temperature on the self-cleaning performance of TiO2 coated surfaces.The effect of humidity was tested at 20, 40, 60 and 80 % of relative humidity in testing chambre, the temperature was kept constant at 20 C.The effect of temperature was tested for the 10, 20 and 30 C, and the relative humidity was kept constant at 60 %.It was observed that increasing of relative humidity always led to higher self-cleaning performance.With respect to the temperature effect, a more complicated relationship was observed between the temperature and self-cleaning performance.The lowest self-cleaning ability was observed for the samples tested at 20 C.The highest self-cleaning effect was observed for samples tested at 10 C; this effect was slightly lower for samples tested at 30 C.The best self-cleaning performance was observed for the experimental conditions of 80% RH and 10C.Relative humidity was identified as a key factor influencing the self-cleaning ability of TiO2 coated cement pastes.