Band Gap Tailored Zn(Nb1-xVx)(2)O-6 Solid Solutions as Visible Light Photocatalysts

Abstract

Zn(Nb1-xVx)(2)O-6 solid solutions (0.01 <= x <= 0.1) were synthesized by incorporation of V into the lattice of ZnNb2O6 by solid-state reaction. The wide-band-gap semiconductor ZnNb2O6 (3.98 eV) became visible-light-active with the band gap energy shifted down to ca. 2.5 eV. Physical characterization with XRD, XPS, and XANES revealed that homogeneous solid solutions were synthesized, which showed systematic variation of electronic structure with concentration of incorporated vanadium. Theoretical band structure calculation indicated that d orbitals of vanadium were responsible for the band gap reduction by forming the bottom part of the conduction band of the solid solution. All V-incorporated solid solutions loaded with RuO2 as a cocatalyst showed photocatalytic activities for H-2 or O-2 production from aqueous solutions of sacrificial reagents under visible light irradiation (lambda >= 420 nm) and RuO2(3 wt %)-loaded Zn(Nb0.94V0.06)(2)O-6 showed the highest activity