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

Abstract

TiO2/SiO2 films were deposited on glass substrates by sol-gel method, and the effects of SiO2 on the photocatalysis and hydrophilicity of TiO2 films were studied. Zeta potential measurements show that SiO2 can effectively inhibit the growth of TiO2 colloidal particles, and improve the stability of sols. XRD and AFM observations discover that, with the increase of SiO2, the size and crystallinity of TiO2 particles, and the porosity and roughness of films all gradually decrease. XPS and FTIR analyses indicate that SiO2 also affect the composition of the films. In addition, the blue shift of the absorption boundary gradually increases with SiO2. The fitting results show that the photocatalytic reaction of films basically follows the first-order kinetics law. The films with 15% SiO2 exhibit the best photocatalytic activity, whose degradation efficiency is about twice that of the pure TiO2 films. The films with 20%wt SiO2 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 SiO2 own the best overall performance.