Aspect Ratio-tunable Magn（?）li Phase W₁₈O₄₉ And Pt/W₁₈O₄₉ Nanorods:Preparation,Characterization,and Photoelectrochemistry Application

With the rapid development of economy, energy and environmental issues had increasingly become the focus issue. Photoelectrochemical technology was a kind of non-polluting advanced oxidation technology that organic pollutants degradation and new energy conversion were conducted with solar-driven. As photoelectrochemical process catalyst, several requirements should be satisfied:First, strong visible light adsorption ability; Second, Fast photo-generated electron transport properties; Third, Good stability. Magneli phase tungsten oxide is an important semiconductor photocatalyst and Dye-sensitized Solar Cell （DSSC） cathode material, which has been used in the field of photovoltaic and photocatalytic optoelectronics research field by many researchers. Magneli phase W18O₄9 has monoclinic structure and one-dimensional W18O₄9 nanorods has good electrical conductivity and rich oxygen vacancy, optical band-gap is 2.6-3.0 eV, making it good adsorption property to visible light. All the characteristics of W18O₄9 nanorods make it suitable to use as new visible light photocatalyst and cathode material for Dye-sensitized Solar Cell. This paper carried out the following work:Study the influence of different source of tungsten concentration and annealing temperature on length-diameter ratio and phase composition of W18O₄9 nanorods. Then Pt-nanoparticles was loaded on W18O₄9 sample with optical aspect ratio. Last, the properties of photodegradating organic plllutants:methylene blue （MB）, methyl orange （MO）, Rhodamine B （RhB） and using as electrode material of DSSC was studied.Firstly, （NH4）2WO₄ precursors were prepared by hydrothermal method with different concentration of Na2WO₄ solution. Then different length-diameter ratio W18O₄9 nanorods were synthesized by pyrolysing （NH4）.WO₄in the atmosphere of 5 % vol H2/Ar. The results demonstrated that:when the synthetic condition is tungsten source concentration is 0.05 mol/L and annealing temperature is 650 ℃, the obtained W18O₄9 nanorods have the most optimal length-diameter ratio.Secondly, Pt-nanoparticles were loaded on W18O₄9 nanorods which was prepared with the most optimum synthesis condition. Chloroplatinic acid solution was used as Pt source and ethylene glycol was used as solvent and reducing agent, the Pt/W18O₄9 nanorods were obtained.Finally, the photocatalytic experiments of degrading MB, MO and RhB were conducted with W18O₄9 and Pt/W18O₄9 nanorods that had most optimal length-diameter ratio under visible light irradiation. The results showed that:the W18O₄9 sample and Pt/W18O₄9 sample prepared under optimal synthetic conditions had the best photocatalytic activity. W18O₄9 sample with most length-diameter ratio has good photocatalytic effect on MB, and the photocatalytic efficiency reached to 67%, but the photocatalytic activities to MO and RhB should be improved. Compared with W18O₄9 nanorods, The photocatalytic degradation efficiency of Pt/W18O₄9 nanorods was improved obviously, its photocatalytic degradation efficiencies to MB, MO and RhB were reached to 98%,72% and 54%, respectively. Photoelectric performance test showed that WONRs-2 and Pt/WONRs-2 counter electrodes which were prepared by different process; after assembled into devices, the photoelectric conversion efficiency reached to 5.35% and 5.68%, respectively.