Photocatalytic Properties and 121Sb Mössbauer Spectra of Antimonic Acid Fine Nanoparticles Prepared by Soft Chemical Solution Process

Abstract

Two kinds of dispersed nanoparticle photocatalysts of antimonic acid, HSbO 3 ·nH 2 O, namely, SbI and SbII, were prepared separately by the direct reactions of an aqueous H 2 O 2 solution with Sb alkoxide complex, Sb(O-i-C 3 H 7 ) 3 and metallic Sb powder according to a soft chemical solution process. Their photocatalytic properties were evaluated from methylene blue (MB, C 16 H 18 N 3 SCl) degradation. SbI showed very strong adsorption capability and high photocatalytic activity under UV light irradiation. The average rates of MB degradation were estimated to be 2.403 x 10 -5 m mol h -1 for SbI and 4.01 x 10 -6 m mol h -1 for SbII. To investigate the reason for their difference in photocatalytic MB degradation, the two Sb-based photocatalysts were characterized by 121 Sb Mossbauer spectroscopy in connection with powder X-ray diffraction and photoabsorption property measurement. The lattice parameters, particle sizes, and relative surface areas were estimated to be 10.372(3) A, 35 nm, and 43.5 m 2 g -1 for SbI and 10.362(4) A, 70 nm, and 31.4 m 2 g -1 for SbII, respectively. Valuable information was obtained on valence state and coordination structure of Sb contained in them. These results revealed that SbI had the advantages of high dispersion, fine crystallinity, and large relative surface area as well as only containing the octahedrally coordinated Sb 5+ species with d 10 electronic configuration, resulting in having the high photocatalytic activity for MB degradation under UV light irradiation. A small amount of Sb 3+ species with d 8 electronic configuration should be considered to be the main reason the photocatalytic performance of SbII for MB degradation was definitely lower than that of SbI.