Investigation of the gas sensing properties of Au/MnOx: response to CO exposure and comparison to Pt/SnO2
✍ Scribed by Srinivasan, Bharat; Gardner, Steven D.
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 240 KB
- Volume
- 26
- Category
- Article
- ISSN
- 0142-2421
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✦ Synopsis
The surface conductivity changes of 2 at.% and 2 at.% have been measured during Au/MnO x , MnO x Pt/SnO 2 cyclical exposures to CO and dry air at 130 ÄC. At each stage of the gas exposures, the corresponding surface compositions were determined using x-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS). The results have been used to gain insight into the surface processes that are responsible for the observed conductivity behavior. Upon CO exposure, the extent of conductivity increase is di †erent for each specimen and a synergistic interaction between Au and is demonstrated. Whereas exposure to dry air (or oxygen) causes the MnO x conductivity of to decrease, the and specimens continue to exhibit positive changes in Pt/SnO 2 Au/MnO x MnO x surface conductivity. This is believed to be due to sufficiently high partial pressures of oxygen that transform the materials from n-type semiconductors to p-type. The surface analysis data implicate the importance MnO x -based of hydroxyl groups and/or adsorbed water to the CO gas sensing mechanism on all three materials, but there is evidence suggesting that their role is di †erent with respect to and The potential advantages of Au/MnO x Pt/SnO 2 . combining and into a single gas sensor are also considered.