Influence of oxygen deficiency on the synthesis of tungsten oxide and the photocatalytic activity for the removal of organic dye

Self-assembly flower-like WO3/W18O49 and W15O49 were synthesized through a facile solvothermal method. By reducing the content of oxygen, the phase of WO3/W18O49 changes to pure W18O49 and the morphology of the W18O49 shows an obvious evolution from nanowire to flower-like W18O49 assembled by nanoneedle. The crystallite size of WO3/W18O49 and W18O49 are 29.85 nm and 14.13 nm, respectively. The photocatalytic activity of W18O49 UV-light irradiation is about 8 times as high as that of WO3/W18O49. This enhanced activity is attributed to smaller crystallite size and larger surface area. Furthermore, XPS analyses reveal that the lattice oxygen reduces under N-2 atmosphere. The increasing of oxygen vacancy results in a narrowing bandgap and strong light absorption performance. By combining the results of the transient photocurrent and electrochemical impedance measurements, the electron-hole pair separation rates and carrier migration rates of the W18O49 have been greatly improved. (C) 2016 Elsevier B.V. All rights reserved.