Synthesis, surface and optical properties of Ag2Cu(VO3)4 and Cu(VO3)2 vanadates

Ag2Cu(VO3)(4) and Cu(VO3)(2) were prepared via the sol-gel chemical synthesis. The phase formation was confirmed by X-ray powder polycrystalline diffraction (XRD) measurements. The surface properties were measured with the scanning electron microscope (SEM), energy dispersive spectra (EDS), transmission electron microscopy (TEM), and nitrogen adsorption-desorption isotherms. The optical properties and the band-gap structures were investigated. The vanadates have efficient optical absorption in the UV to visible wavelength region with an indirect allowed transition. Ag2Cu(VO3)(4) has smaller band gap (1.85 eV) than that of Cu(VO3)(2) (2.03 eV). The narrowed band gap is due to the hybridization between the Ag-4d and O-2p in the valence band. The photocatalysis was investigated by photodegradation of methylene blue (MB) solutions excited by the light with wavelength longer than 420 nm. Correspondingly Ag2Cu(VO3)(4) has more efficient photocatalytic activity on MB photodegradation than that of Cu(VO3)(2). The photocatalytic mechanisms were suggested according to the band positions and the trapping experiments. (C) 2016 Elsevier B.V. All rights reserved.