Yellow tungsten oxide, which is well-known as tungsten trioxide or WO3, is a semiconductor material developed in recent years with excellent gasochromic property. So, WO3 is often used as a gasochromic material for applications of different gas sensors such as NO2 sensors. The gasochromic property of yellow tungsten oxide is often explained by the polaron model. The following is an example given by the researchers.
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Taking hydrogen as an example, hydrogen molecules are chemically adsorbed and decomposed on the surface of catalysts (such as Pt); then, H diffuses and migrates along the pores of the film; reacts with WO3 to generate polarons and H2O, and H2O escapes, and the "transition" of polarons from one lattice (W5+) to another (W6+) results in light absorption and gasochromic phenomenon. Therefore, the research on WO3 gasochromic property mainly focuses on promoting the diffusion of substances during the discoloration process.
