Combustion synthesis-aqueous hybridization of nanostructured graphene-coated silicon and its dye removal performance

Abstract

An ultra-fast and green combustion synthesis methodology is employed to reduce quartz sea sand (SiO2) into a Mg2Si(Si)/MgO nanostructured material. Moreover, highly conductive graphene nanosheets with a specific bulk electrical conductivity of 27 S cm2 g−1 are prepared by the molten salt exfoliation of graphite in molten salt. A simple one-pot acid treating of the combustion synthesized material, and graphene nanosheets leads to the preparation of a nanostructured Si-graphene hybrid material (NSG) with clean interface, promoting the dye adsorption and photocatalyric activity of the nanostructured material, outperforming the commercially available silicon nanoparticles. The dye removal performances of the silicon materials (1.0 g L−1) are evaluated using methylene blue as the model dye with the initial concentration of 50 mg L−1 in dark and under visible blue LED irradiation with the peak output at the wavelength of 475 nm. While commercial Si nanoparticles exhibit neither considerable dye adsorption nor photocatalytic activity, 69 present of the dye is absorbed at the adsorption equilibrium within 50 min of exposure to NSG, followed by the complete dye removal upon LED light irradiation within 300 min. The enhanced adsorption and photocatalytic performance of NSG is attributed to the unique morphology of NSG, in which highly crystalline few layer graphene nanosheets with low level of structural defects are in contact with silicon semiconductor nanocrystals.