Facile construction of magnetic α-Fe2O3/SiO2 composite aerogels for enhanced adsorption and visible light photocatalytic activity

Magnetic iron oxide is a typical narrow-band gap semiconductor photocatalyst, but its inherent magnetic aggregation effect and high electron-hole recombination rate seriously affect its photocatalytic performance. Here, alpha-Fe2O3/SiO2 composite aerogels were prepared by combustion technology for the first time. The unique structure of alpha-Fe2O3/SiO2 composite aerogels with amorphous silica coated with nanocrystalline iron oxide was confirmed. The composite aerogels exhibited a high specific surface area (479 m2 g-1 when calcined at 500 degrees C), so that they have excellent adsorption properties for organic pollutants (MB, RhB and TC) and Cr(vi). The composite aerogels with a Fe : Si molar ratio of 1 : 2 showed the best visible light photocatalytic properties for MB, RhB and TC. Based on the study of the band gap width, photocurrent density, transient photocurrent response, impedance of photocatalysts, and the unique structure of the composite aerogels, the mechanism of photocatalytic enhancement of composite aerogels was proposed. Finally, the mechanism of the preparation of alpha-Fe2O3/SiO2 composite aerogels by combustion synthesis was analyzed. It is a potential technology for preparing high performance composite aerogel photocatalysts by high efficiency combustion technology.