Understanding the Sensing Mechanism of WO3 Based Gas Sensors.

The first commercially available semiconducting metal oxide gas sensor, patented by Taguchi in the 1970s, was based on SnO2. Even today, most commercially produced sensors are based on SnO2. As computing power becomes more prevalent and metal oxide gas sensors are used in a broader range of applications, materials with complementary sensing characteristics will be needed. WO3 is a promising material that shows high responses to volatile organic compounds and NO2. Interestingly, humidity is reported to have an oxidizing effect on the material, which is the opposite of what is commonly reported for SnO2. Here the surface reaction which is responsible for the sensing mechanism of NO2 is examined using diffuse reflectance infrared Fourier transform spectroscopy. The effect of humidity on the sensor response is understood and a comparison to SnO2 is made.