Photocatalytic activity under visible light irradiation of cement based materials containing TiO2-xNy nanoparticles

Self-cleaning activity of Portland cement pastes blended with nanoparticles of titanium oxynitride (TiO2−xNy ) was studied. Samples with various amounts of TiO2−xNy (1% and 3%) were evaluated under irradiation of UV and visible light, and with two curing ages (65 hour and 28 days). Rhodamine B was the pigment used and its loss of color on the cement pastes was carried out using a Spectrometer UV/Vis measuring the coordinates CIE (Commission Internationale de l’Eclairage) L ∗ , a ∗ , b ∗ . Discoloration of Rhodamine B on the surface of the samples was established as the photocatalytic efficiency coefficient (e). In addition, samples with TiO2 nanoparticles (1% and 3%) were studied under the same conditions and their performances were compared with TiO2-xNy . The presence of nitrogen in the tetragonal structure of TiO2 was evidenced by X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectrophotometry and Carbon, Hydrogen and Nitrogen (CHN) analysis. The band gap for TiO2 and TiO2-xNy was determined by the transformed Kubelka-Munk function ( [F (R∞) hv] 1/2 ) . The results have shown a similar behavior for both additions under UV light irradiation, with 3% being the addition with the highest photocatalytic efficiency obtained in the early ages of curing time. TiO2−xNy showed activity under irradiation with visible light, unlike TiO2, which could only be activated under UV light. At the late curing ages, the samples with 3% of TiO2-xNy showed the highest efficiency under irradiation of UV and visible light.