Preparation of three-dimensional interconnected mesoporous anatase TiO2-SiO2 nanocomposites with high photocatalytic activities

In this article, we report the preparation of a three-dimensional (3D) interconnected mesoporous anatase TiO2-SiO2 nanocomposite. The nanocomposite was obtained by using an ordered two-dimensional (2D) hexagonal mesoporous anatase 70TiO2-30SiO2-950 nanocomposite (crystallized at 950 °C for 2 h) as a precursor, NaOH as an etchant of SiO2via a “creating mesopores in the pore walls” approach. Our strategy adopts mild conditions of creating pores such as diluted NaOH solution, appropriate temperature and solid/liquid ratio, etc. aiming at ensuring the integrities of mesopores architecture and anatase nanocrystals. XRD, TEM and N2 sorption techniques have been used to systematically investigate the physico-chemical properties of the nanocomposites. The results show that the intrawall mesopores are highly dense and uniform (average pore size 3.6 nm), and highly link the initial mesochannels in a 3D manner while retaining mesostructural integrity. There is no significant change to either crystallinity or size of the anatase nanocrystals before and after creating the intrawall mesopores. The photocatalytic degradation rates of rhodamine B (RhB, 0.303 min−1) and methylene blue (MB, 0.757 min−1) dyes on the resultant nanocomposite are very high, which are 5.1 and 5.3 times that of the precursor; even up to 16.5 and 24.1 times that of Degussa P25 photocatalyst, respectively. These results clearly demonstrate that the 3D interconnected mesopores structure plays an overwhelming role to the increments of activities. The 3D mesoporous anatase TiO2-SiO2 nanocomposite exhibits unexpected-high degradation activities to RhB and MB in the mesoporous metal oxide-based materials reported so far. Additionally, the nanocomposite is considerably stable and reusable. We believe that this method would pave the way for the preparation of other 3D highly interconnected mesoporous metal oxide-based materials with ultra-high performance.

Graphical AbstractAn ordered mesoporous anatase-silica nanocomposite with 3D interconnected mesopores presents unexpectedly high photocatalytic degradation activities toward RhB and MB dyes, significantly higher than the corresponding non-interconnected mesoporous precursor and a commercial Degussa P25 photocatalyst.Figure optionsDownload as PowerPoint slide