Interfacial design of nano-TiO2 modified recycled concrete powder for building self-cleaning

In this study, nano-TiO2 was loaded on recycled concrete powder (RCP) to synthesize RCP/TiO2 composites (RCPT) via a mechanochemical method, which can be employed to create smart surfaces with the functions of antipollution and self-cleaning in urban buildings. Microstructure of the as-prepared RCPT were characterized by multiple testing technologies. Based on the microstructure information, the bonding state between nano-TiO2 and RCP was confirmed and the distribution model of nano-TiO2 was proposed. The self-cleaning performance of RCPT was evaluated by photocatalytic decolorization of RhB. Our results clearly showed that nano-TiO2 was homogenously immobilized on RCP, and RCPT exhibited higher self-cleaning efficiency than pure TiO2 due to the enhanced photocatalytic efficiency and hydrophilicity. Specifically, the charge transfer between nano-TiO2 and RCP can boost the photocatalytic efficiency, and the enhanced surface roughness of RCPT contributed to improve the hydrophilicity. Our work reveals the effect of the interaction between nano-TiO2 and RCP on the self-cleaning performance, and provides some guidance on the preparation of low-cost nano-TiO2 composite self-cleaning material via a facile method.