Effects and mechanism of SiO₂ on photocatalysis and super hydrophilicity of TiO₂ films prepared by sol-gel method

TiO 2 /SiO 2 films were deposited on glass substrates by sol-gel method, and the effects of SiO 2 on the photocatalysis and hydrophilicity of TiO 2 films were studied. Zeta potential measurements show that SiO 2 can effectively inhibit the growth of TiO 2 colloidal particles, and improve the stability of sols. XRD and AFM observations discover that, with the increase of SiO 2 , the size and crystallinity of TiO 2 particles, and the porosity and roughness of films all gradually decrease. XPS and FTIR analyses indicate that SiO 2 also affect the composition of the films. In addition, the blue shift of the absorption boundary gradually increases with SiO 2 . The fitting results show that the photocatalytic reaction of films basically follows the first-order kinetics law. The films with 15% SiO 2 exhibit the best photocatalytic activity, whose degradation efficiency is about twice that of the pure TiO 2 films. The films with 20%wt SiO 2 have the best super hydrophilicity, whose water contact angle (WCA) drops to 2° in 3s. More significantly, its super hydrophilicity can last for more than 6 days under dark, that is, the films obtain an enhanced durable super hydrophilicity. In summary, the films with 15%wt–20%wt SiO 2 own the best overall performance.