Preparation, Characterization And Photoelectrochemical Application Of Tungsten Oxides

With the rapid development of the world economy, the fossil energy is faced with the danger of exhaustion. The contamination generated and emitted in the production and daily life makes the environment deteriorate. As a new green cell, the dye-sensitized solar cell (DSSC) is an effective measure to solve the energy shortage problem. The photocatalytic degradation of pollutants technology is an important method of environmental governance. WO3 have various phases, including tetragonal, monoclinic, orthorhombic, cubic, hexagonal and triclinic. W18O49 is the monoclinic crystal of the hexagonal unit cell, and it has good electric conductivity. Tungsten oxide (WOx) is an n-type semiconductor material, with narrow band gap ranging from 2.4 to 3.2 eV. It can absorb not only the ultraviolet light but also the visible light. With good photocatalytic and photoelectrochemical properties, it can be used for the photocatalytic degradation of pollutants and the counter electrode of DSSC. The innovative point of this thesis:the preparation of the three-dimensional ordered macroporous of WOx, the photocatalytic degradation efficiency is 91.1%.This thesis focuses on following works:(1) Synthesize the monodisperse poly methyl methacrylate (PMMA) microspheres with the emulsion polymerization and non-emulsion polymerization, and assemble the PMMA colloidal crystal template with the centrifugation and water bath drying at constant temperature. Then use ammonium tungstate, tungsten trioxide and the tungsten powder material as a precursor to prepare three-dimensional ordered macroporous (3DOM) tungsten oxide. The samples are characterized by XRD and SEM techniques. The results shows that:1) by dissolving the tungsten trioxide in the hydrofluoric acid, the sample prepared has a small amount of non-stoichiometric WOx; 2) use tungsten powder to prepare 3DOM WO3 through the sol-gel method, the pore diameter structure is more ordered, and the pore wall connectivity is good.(2) W18O49 of different morphologies are fabricated by a facile solventinduced assembly menthod. The samples are characterized by SEM, XRD and Raman techniques et al. The results shows that:nanowire, shuttle and sea urchin stoichiometric W18O49 have been prepared.(3) Use the above prepared W18O49 sample as the photochemical catalyst, and carry out the photocatalytic degradation of methyl orange (MO) experiment under the illumination of UV-visible light. The results shows that:among the three morphologies, the W18O49 nanowire has the best photocatalytic effect, the photocatalytic degradation efficiency of the W18O49 nanowire after 90 minutes of illumination can be as high as 91.1%. Use the prepared W18O49 samples of different morphologies as the DSSC counter electrode materials respectively, the FTO glass with TiO2 thin films which used as anode is assembled into DSSC cells, photoelectronic conversion efficiency of the W18O49 nanowire DSSC(2.46%) is higher than the other two species.