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 W18O49 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 N2 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.