BiOBr@SiO2 flower-like nanospheres chemically-bonded on cement-based materials for photocatalysis

Abstract Endowment of photocatalytic property on the surface of concrete structure can contribute to the self-cleaning of the structure and purification of the polluted environment. We developed a nano-structured BiOBr@SiO 2 photocatalyst and innovatively used for surface-treatment of cement-based materials with the hope of attaining the photocatalytic property in visible-light region and surface modification/densification performances. The SiO 2 layer on the flower-like BiOBr@SiO 2 helps to maintain a stable distribution of the photocatalyst, as well as achieving a chemical bonding between the coating and the cement matrix. Results showed that the color fading rate of during the degradation of Rhodamine B dye of the BiOBr-cem sample is 2 times higher compared with the commonly studied C, N-TiO 2 -cem sample. The photo-degradation rates of samples BiOBr-cem and BiOBr@SiO 2 -cem are 93 and 81% within 150 min, respectively, while sample BiOBr@SiO 2 -cem reveals a denser and smoother surface after curing for 28 days and pore-filling effect at size within 0.01–0.2 μm when compared with untreated samples. Moreover, additional C-S-H gel can be formed due to the pozzolanic reaction between BiOBr@SiO 2 and the hardened cement matrix. Both advantages of the BiOBr@SiO 2 favor its application for surface-treatment of hardened cement-based material to acquire an improved surface quality, as well as durable photocatalytic functionality.