Photocatalytic and photophysical properties of a novel series of solid photocatalysts, BiTa1−xNbxO4 (0⩽x⩽1)

BiTa1−xNbxO4 (0⩽x⩽1) solid photocatalysts were prepared by solid-state reaction and characterized by powder X-ray diffraction and Rietveld structure refinement. The structure of BiTa1−xNbxO4 (x=0.0 and 0.5) is triclinic. However, the structures of x=0.2, 0.8 and 1.0 are orthorhombic. The H2 evolution was obtained from an aqueous CH3OH/H2O solution and from pure H2O with BiTa1−xNbxO4 (0⩽x⩽1) under UV irradiation. The orthorhombic photocatalysts exhibit much higher activity than that of triclinic photocatalysts. The orthorhombic photocatalyst at x=0.2 showed the highest activity. An UV–vis diffuse reflectance spectroscopy measurement revealed that the band gap of orthorhombic photocatalysts is more narrow than that of triclinic photocatalysts.