Photocatalytic cement-based materials: Comparison of nitrogen oxides and toluene removal potentials and evaluation of self-cleaning performance

Using cement-based building materials as a matrix for nano-photocatalysts is an important development for the large scale application of photocatalytic technologies. Air pollution mitigation and self-cleaning surface are two major applications of photocatalytic building materials. In this study, a comparison was made to evaluate the performance of TiO2 modified concrete surface layers for NOx and VOC degradation. The self-cleaning performance of TiO2 modified self-compacting mortars (SCM) developed for decorative applications was also evaluated. The results show that the photocatalytic conversion of toluene by the TiO2 modified surface layer was not detected, although NOx could be effectively removed under the same conditions. The presence of toluene did not influence the NOx removal process. TiO2 modified SCM were found to be effective in the discoloration of rhodamine B under UV and strong halogen light irradiation. The level of adsorption of the air contaminants onto the active sites of the cement-TiO2 composite was identified to be the key factor determining the subsequent photocatalytic efficiency.