Gas Sensing Characteristics of WO3 (II)

Details: Category: Tungsten Information; Published on Thursday, 05 February 2015 17:58; Written by cq; Hits: 1671

(2) Gas sensing characteristics to H2S

Hydrogen sulfide (H2S) is a malodorous toxic gas, as the one of representative reducing inorganic gases, which draws researcher’s interests. Studies showed the nanowires and platelets performed more quickly response to the same concentration of H2S gas in the same working temperature compared to the nanoparticles. This is because the larger surface area provides more adsorption desorption sites and results in a higher sensitivity. The sensing mechanism of WO3 to H2S is also provided.

First, the atmospheric oxygen adsorbs electrons from the conduction band (CB) of WO3 and occurs on the oxide surface in the form of O2-and O-

O2(air) + e-→O2(ads)-

O2(ads)-+e-→2O(ads)-

In this way, oxygen adsorption reaction creates a thin electron-depleted layer at the surface of WO3. Then H2S reacted with the adsorbed oxygen species according to the following formula

H2S + 3O( ads)-→SO2+H2O + 3e-

Thus, the resistance of WO3 decreases. As the detection of H2S was usually based on the reaction between H2S molecules and surface oxygen of WO3.

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