Different Hydrogenation Temperatures Affect Tungsten Oxide

To further investigate the morphology and structural changes of the samples after hydrogenation, tungsten oxide can be characterized by transmission electron microscopy. It can be seen from the figure that when the hydrogenation temperature is 300 ° C, the W-300 maintains a good morphology and is about 100 nm in size. The hydrogenation temperature is 400 ℃, W-400 size significantly smaller, are below 50nm.

At a hydrogenation temperature of 300 ° C, the edges of the W-300 nanoparticles became obscured and disordered to form a surface disorder layer of about 2 nm, a phenomenon indicating that the surface structure was destroyed and surface oxygen defects were also formed therein. When the hydrogenation temperature reaches 400 ° C, the disordered area of the W-400 nanoparticles is further enlarged, and the crystallinity of the non-disordered area also drops significantly.

As can be seen from the Fourier transform plots for the W-300 and W-400 samples, the 90 ° and atomic planes are clearly identified. This matches the monoclinic phase tungsten oxide crystal structure, indicating that the more crystalline region is still tungsten oxide. After further analysis, we found that a small part of the lattice distortion in the crystal region. This may be the reason for the appearance of some tungsten oxide peaks in XRD. This partially twisted lattice region forms a tungsten oxide structure. However, due to too little content, it is not shown in the Fourier transform and Raman plots. In addition to oxygen vacancies exist in the edge of the disorder region, while there are very few parts of the tungsten oxide surface (lattice distortion generated).

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