Tantalum Tungsten Bronze

Tungsten oxide is a kind of transition metal oxide, its special property makes it be widely used in electrochromic device, gas sensor, separating material and so on. W ion in tungsten bronze belongs to changeable valence state, when introduce transition metal into crystalline structure, valence state of W transits between Ｗ^６＋，Ｗ^５＋ and Ｗ^４＋, unstable oxygen valance will form in lattice, surface of material will show defects. As a result, tungsten oxide shows special physical and chemical property. Tantalum belongs to transition metal which can be used as electrode material. Also dimension of Ta5+ is small and active, we can judge that doping tantalum can have great influence on its electric chemical property.

Preparation
1. Weighing 2g Na₂WO₄.2H₂O in reaction still with politef lining. Add in redistilled water, magnetic stirring and dissolving.
2. Adding a certain amount of 3 mol/L hydrochloric acid, control the whole reaction system pH lower than 1.5. Adding 0.05 mol/L TaCl5 and 0.5 mol/L NH₄(SO₄)2, stirring for 2hours and sealed the reaction still.
3. Heating it for 48h under 170 ℃, wash the reaction producer with distilled water to neutral, then put it in －40℃ lyophilizer.

Lead tantalum into hexagonal tungsten oxide structure by hydrothermal method, nano wire structure TaxWO₃ is obtained, the sample is even and with high purity. When Ta and W ratio in TaxWO₃ is 0.04, it reaches the settled limiting value of tantalum doping in tungsten oxide. Doping low valance state and big diameter tantalum ion into tungsten oxide, its cell parameters get affected, lattice is changed, oxygen valence on the surface of material ratio enlarged, the electron transition ability decreases, the catalytic property of material improves. Under acid condition, reduction of TaxWO₃ for H+ is more stable, it has potential application in fuel cell field.

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