Synchronous role of coupled adsorption and photocatalytic oxidation on ordered mesoporous anatase TiO2–SiO2 nanocomposites generating excellent degradation activity of RhB dye

Abstract

In this paper, we report a synchronous role of coupled adsorption and photocatalytic oxidation on ordered 2-D hexagonal mesoporous TiO2–SiO2 nanocomposites with large pore channels (>4.0nm) and high specific surface areas (>70m2g−1). These mesoporous frameworks consist of anatase TiO2 nanocrystals and amorphous SiO2 nanomatrixes, which link mutually, coexist to form unique composite-walls, providing unprecedented spaces for “the synchronous role of coupled adsorption and photocatalytic oxidation”. SiO2 nanomatrixes are excellent adsorbents, providing better adsorption centers and enriching organic pollutant molecules; while anatase nanocrystals behave as photocatalytic active sites to oxide the organic molecules pre-enriched by the surrounding SiO2 particles. Moreover, the high accessible surface areas can provide more adsorptive and photocatalytically active sites; and the large mesopore channels allow the reactive molecules to diffuse more easily both into and out of the inner surfaces before and after photocatalytic reactions, respectively. Our strategy realizes the synchronous role by adjusting Ti/Si ratios, the number of surface hydroxyls, the size and crystallinity of the anatase nanocrystals on the unique composite-frameworks. The cationic rhodamine-B (RhB) dye is used as the target pollutant to characterize the adsorption performance and photocatalytic activities. Our results show that the synchronous role results in excellent photocatalytic degradation activity (k=0.231min−1), which is much higher than that of Degussa commercial P25 photocatalyst (k=0.0671min−1).