Nano-Tungsten Oxide Electron Injection Effect

Electrochromism of nanotungsten oxide is an electron injection effect. Oxygen ions have a conductive effect in nano-tungsten oxide. When an oxygen ion near the negative electrode leaves the original position, the corresponding tungsten ion becomes a highly active ion.

Highly active tungsten ions can be reduced by one electron and the presence of low-valence tungsten ions discolors the nano-tungsten oxide. The ions near the electrode can transfer the electrons it acquires to similar ions and reacquire electrons from the electrodes. This process continues so that the color of the nano-tungsten oxide constantly changes color from the negative electrode to the positive electrode. The fading is due to the loss of electrons from low-valence ions to high prices, which is equivalent to the inverse of the above process.

The conventional tungsten oxide bulk has no electrochromic phenomenon, and the nano-sized tungsten oxide bulk has obvious electrochromic effects as described above. This is due to the surface effect of the nanomaterials, so that oxygen ions at the surface of the grains can migrate in the nano-tungsten oxide. Tungsten ions have a higher activity than conventional nano-tungsten oxide and can combine or separate from electrons under the influence of an applied electric field. Therefore, the nano-tungsten oxide can be discolored with applied voltage. However, in conventional tungsten oxide bulk tungsten oxides, oxygen ions cannot migrate, and tungsten ions do not have sufficient activity. So nano-tungsten oxide does not change color. The difference in scale between nanomaterials and conventional materials has led to dramatic changes in physical properties, demonstrating the novel properties of nanomaterials.

Conclusion: Nano-sized tungsten oxide bulks exhibit electrochromic properties that are not found in conventional materials. Structural analysis showed that the microstructure and phase structure of nanometer tungsten oxide did not change significantly. The physical mechanism of discoloration is that electrons are injected into the material, causing a portion of the high-priced tungsten ions to become cheap, resulting in a change in the color of the material. The coloring/fading state can be changed by simply changing the polarity of the voltage, and the discoloration does not affect the structure and appearance of the material and damage. Therefore, the electrochromic effect of nano-sized tungsten oxide bulks may lead to some new applications.

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