Band gap tailored ZniNb_1-xv_xO₆ solid solutions as visible light photocatalysts

Zn(Nb_1-xV_x)₂O₆ 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 visiblelight-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 orbitais 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 H₂ or O₂ production from aqueous solutions of sacrificial reagents under visible light irradiation (λ > 420 nm) and RuO₂(3 wt %)-loaded Zn(Nb _0.54V_0.36)O₆ showed the highest activity.