Preparation of the Visible Light Responsive N 3−-Doped WO 3 Photocatalyst by A Thermal Decomposition of Ammonium Paratungstate

Preparation of the visible light responsive N 3−-doped WO 3 photocatalyst by a thermal decomposition of ammonium paratungstate

Ammonium paratungstate (or APT) is a white crystalline salt of ammonium and tungsten, with the chemical formula (NH₄)₁₀(H₂W₁₂O₄₂)·4H₂O.

Ammonium paratungstate is produced by separating tungsten from its ore. Once the ammonium paratungstate is prepared, it is heated to its decomposition temperature, 600 °C. Left over is WO3, tungsten(VI) oxide. From there, the oxide is heated in an atmosphere of hydrogen, reducing the tungsten to elemental powder, leaving behind water vapor. From there, the tungsten powder can be fused into any number of things, from wire to bars to other shapes.
 

The nitrogen doped WO3 (N-WO3) photocatalyst was successfully prepared by a thermal decomposition of an ammonium paratungstate [(NH4)10W12O41·5H2O] containing NH4+ ions as a nitrogen source. The N-WO3 prepared at 673–873K efficiently absorbed visible light in longer wavelength regions as compared to a commercial N-free WO3. Although small amount of Pt particles must be deposited on the catalyst surfaces, the N-WO3 photocatalysts were found to decompose gaseous methanol into CO2 and H2O under visible or solar light irradiations. As well as, the Pt particles on the N-WO3 surfaces to enhance the photocatalytic activity showed an oxidation catalysis property at low temperatures of 323–333K. These results suggest that the N-WO3 deposited with Pt particles can effectively utilize the sunlight as light and/or heat sources.

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