Oxygen-deficient Tungsten Oxide Catalytic Mechanism

Oxygen-deficient tungsten oxide can degrade methyl orange solution, but the degradation reaction belongs to the catalytic reaction or ordinary chemical reaction, still need further verification. To verify whether the sample degrades methyl orange is a catalytic reaction or a chemical reaction, whether the crystal structure of the oxygen-deficient tungsten oxide has been degraded after the degradation experiment can be observed to determine its reaction catalytic mechanism.

By observing the XRD pattern of oxygen-deficient tungsten oxide, one can determine if the crystal structure of the sample in the methyl orange solution remains intact. The oxygen-deficient tungsten oxide was placed in 10 ml of deionized water and 10 ml of methyl orange soaked for a certain period after drying, and observed the sample XRD spectra, focusing on the crystal peak position and relative intensity changes.

When the sample has not been soaked, monoclinic tungsten [55] corresponds to [010], [511] diffraction peak stronger. When immersed in deionized water or methyl orange for 10 s, the diffraction peaks of the monoclinic tungsten with [110], [200] and [211] crystal orientations are obviously enhanced and the diffraction peaks of tungsten oxide are also enhanced. When the immersion time reaches 60 min, the diffraction peak of cubic tungsten is stronger than the diffraction peak of tungsten oxide.

And the soaking time reaches 2 days, XRD diffraction peak position and intensity has been basically unchanged. After the oxygen-deficient tungsten oxide is soaked in the solution, the thin layer of tungsten oxide on the surface of the material falls off, exposing the tungsten element inside. When soaking time to 60 min, the surface of the thin layer will gradually fall off, the sample's internal structure will be gradually exposed. When the soaking time is longer, the morphology of the sample is basically stable, and the crystal structure of the sample also tends to be stable. The trend of the XRD patterns of the samples immersed in methyl orange and deionized water was consistent. This is not a direct change in the crystal structure caused by the redox reaction between the sample and methyl orange.

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