Fabrication of superhydrophilic self-cleaning SiO2–TiO2 coating and its photocatalytic performance

Generally, superhydrophilic self-cleaning coatings are prepared from semiconductors with photocatalytic properties. Organic pollutants attached to the coating surface can be degraded by its photocatalytic performance realizing a self-cleaning goal. Herein, SiO2–TiO2 composite particles were fabricated by the hydrolysis and precipitation of TiOSO4, and SiO2 microspheres were chosen as carriers, which are inexpensive and environmentally friendly. Then, superhydrophilic self-cleaning SiO2–TiO2 coatings were fabricated by spraying the composites on the surfaces of substrates. The morphology, structure and self-cleaning performance of the SiO2–TiO2 coating were characterized and tested. The results revealed that nano-TiO2 was loaded on the surfaces of SiO2 microspheres uniformly forming a hierarchical micro/nanostructure. The SiO2–TiO2 composite particles exhibited excellent photocatalytic degradation performance, and the degradation rate of methyl orange (10 ppm) was more than 98% under UV irradiation for 40 min. Furthermore, the coating prepared with the SiO2–TiO2 composite particles exhibited superhydrophilicity. A water droplet spreads completely on the coating surface in 0.35 s, and the contact angle reaches 0°. In addition, rhodamine B (RhB) and methylene blue (MB) on the coating surface can be degraded efficiently under sunlight irradiation. The SiO2–TiO2 composite particles can be sprayed directly on the surfaces of concrete, brick, wood, and glass slides. Therefore, the particles showed good adaptability to different substrates. The superhydrophilic property was due to the hydrophilicity of SiO2 and TiO2, the hierarchical micro/nanostructure of the SiO2–TiO2 composites, and the photoinduced superhydrophilicity of TiO2. The above experimental results show that the as-prepared superhydrophilic self-cleaning SiO2–TiO2 coating has a large application potential.