Bi24Ga2O39 for visible light photocatalytic reduction of Cr(VI): Controlled synthesis, facet-dependent activity and DFT study

The sillenite-type Bi24Ga2O39 photocatalysts with different exposed facets were successfully synthesized using a controlled hydrothermal method and their facet-dependent photocatalyic activity was confirmed by DFT calculation. Bi24Ga2O39 micro -tetrahedrons (BGO-T) enclosed by (1 1 1) facets were obtained at 1 M NaOH and micro-cubes (BGO-C) enclosed by (1 0 0) facets were obtained with ammonium hydroxide as mineralizer. The photocatalytic performances of the catalysts were evaluated by the reduction of Cr (VI) in water under irradiation of visible light (lambda > 400 nm). The BGO-C enclosed by {100} facets showed higher photocatalytic activity toward Cr(VI) reduction than the other samples. XPS analysis revealed the reduction of Cr(VI) into Cr(III) happened over Bi24Ga2O39 photocatalyst under visible light illumination. The surface energy calculated by VASP showed that the cleavage energy of (1 0 0) surface was lower than that of (1 1 1) surface, which was consistent with our experimental results. The mechanism on the facet dependent photocatalytic property of Bi24Ga2O39 has been investigated by the surface electronic structures and photoluminescence spectra. (C) 2016 Elsevier B.V. All rights reserved.