Photocatalytic Performance of Cementitious Composites Modified with Second-Generation Nano-TiO2 Dispersions: Influence of Composition and Granulation on NOx Purification Efficiency

This study investigated the influence of the composition of photocatalytic dispersions made with second-generation nano-TiO2 on the air purification performance of photocatalytic cementitious composites. Nine mortar series were prepared, incorporating photocatalytic dispersions of variable content of nano-TiO2, dispersing agent (superplasticizer), and hydrophobic admixture. The total mass content of nano-TiO2 in investigated mortars was kept at the same level. For investigated composites, photocatalytic removal of NOx was evaluated under simulated laboratory conditions mimicking polish autumn/winter irradiation conditions. The results indicate that within the tested range of variability, the dispersion composition significantly influenced the granulation of the dispersed nano-TiO2 particles, which in turn affected the air purification performance of the composites. A predictive model was developed to account for environmental factors potentially influencing photocatalytic performance in urban environments. The model estimated that, depending on environmental conditions and photocatalytic dispersion composition, the composite’s photocatalytic layer could remove up to 1.067 g/m2 of NO2 per year in favorable environmental conditions. Photocatalytic cementitious composites can act as environmentally beneficial composites, contributing to carbon-negative construction practices and improving urban air quality. This highlights the dual benefits of offsetting embedded carbon emissions and enhancing air purification efficiency in sustainable urban infrastructure.