Synthesis Of WO_x Nanostructures And Their Photocatalytic Properties

Metal oxides are the key ingredients for the development of many advanced functional materials and smart devices. Tungsten oxides（WO x） are transition metal oxide with wide range applications. They are applied mainly in chromism, sensing, photocatalysis. Furthermore, tungsten oxides have been being studied for solar-cell, catalysis and Surface Enhanced Raman Scattering as well.Interest in WO_x can be dated back to the 17 t h century. More recently, renewed research interest in WO x was sparked by the discovery of its electrochromic（EC） effect. In comparison to many other functional metal oxide nanostructures, such as TiO 2, ZnO, N iO, and their substoichiometric forms, the study of WO_x chromic properties is much more advanced. Nanostructured WO_x is also a well-studied material for photocatalysis and sensing. While metal oxides such as SnO2, TiO2, ZnO, as well as their various substoichiometric forms, are commonly used in photocatalytic systems and sensors. For solar-cell research, nanostructured WO_x has received relatively little attention. However, the application of WO x in solar cells and photocatalysis should be encouraged, since it offers similar functional properties to TiO2 and ZnO, which are now widely used in the relevant industries.There exit argue that whether the WO₃ or the WO x（x<3） is the active species reacted in chromism, catalysis and other like. For the questions mentioned above, WO x（x<3） and WO₃ with fine morphology were prepared and their photocatalytic properties were investigated as wel. According the works done in this paper, the main results are listed as follows.1. Tungsten oxides（WO_x） with different morphologies were prepared by solvothermal method. The urchin- like WO x with three-dimensional structure had more oxygen vacancies than the WO x nanowires. The morphology influence on the photocatalytic activity was taken into account. The results revealed that the one-dimensional WO x exhibited better photocatalytic activity, which indicated that the one-dimensional structure played the leading role in enhancing the photocatalytic activity.2. Hydrothermal method was adopted to synthesize WO₃ nanoplate. Fine morphology was obtained through optimize parameters, such as precursor concentration, reaction time, p H and capping agent. The photocatalytic activities of WO₃ nanoplates were evaluated by their efficiency in the degradation of pollutants under UV light irradiation. Compared with WO 3 nanoplates, the WO_x（x<3） nanostructures showed enhanced photocatalytic activity.3. The surface photocurrent measurement of the WO 3 nanoplate and the WO_2.72 nanostructures with different morphologies were carried out to analyze the different photocurrent response. The photocurrent value of the WO_2.72 nanowire electrode was about double as high as the urchin- like WO_2.72 nanostructures. While the photocurrent of WO₃ nanoplate was the lowest among three nanostructures. This result was corresponding to the photocatalysis.