HNbxTa1-xWO6 monolayer nanosheets solid solutions: Tunable energy band structures and highly enhanced photocatalytic performances for hydrogen evolution

HNbxTa1-xWO6 monolayer nanosheets solid solutions were successfully synthesized through a top-down method. The crystal structure and morphology of the prepared materials were investigated by X-ray diffraction patterns (XRD), Raman spectra, and transmission electron microscopy (TEM). Atomic force microscopy (AFM) further confirmed that the thicknesses of the nanosheets solid solutions were at a range of 1.50-2.00 nm. As the ratios of Nb increased from x=0.0 to 1.0 in HNbxTa1-xWO6 nanosheets solid solutions, the photo-absorption spectra were red-shifted, showing a decrease in the band gaps (from 3.26 to 3.10 eV), and the flat band potentials were shifted positively (from -0.78 to -0.68 eV). The photocatalytic activities of hydrogen evolution from water for these samples were found to be strongly dependent on their composition, which would increase as the mole ratios of Nb to Ta increases. Among the prepared nanosheets solid solutions, HNb0.7Ta0.3WO6 nanosheets showed the highest photocatalytic activity for H-2 evolution with a rate constant of 1320.0 mu mol h(-1) g(-1). Combining with the photo-electrochemical analyses, precise control of the energy band structure via a solid solution strategy is a useful method for band engineering to develop an efficient photocatalyst. (C) 2016 Elsevier B.V. All rights reserved.