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Investigation of the gas sensing properties of Au/MnO x : response to CO exposure and comparison to Pt/SnO 2
Author(s) -
Srinivasan Bharat,
Gardner Steven D.
Publication year - 1998
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/(sici)1096-9918(199812)26:13<1035::aid-sia453>3.0.co;2-b
Subject(s) - x ray photoelectron spectroscopy , conductivity , adsorption , oxygen , chemistry , analytical chemistry (journal) , spectroscopy , semiconductor , inorganic chemistry , chemical engineering , materials science , environmental chemistry , physics , optoelectronics , organic chemistry , quantum mechanics , engineering
The surface conductivity changes of 2 at.% Au/MnO x , MnO x and 2 at.% Pt/SnO 2 have been measured during cyclical exposures to CO and dry air at 130°C. 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 different for each specimen and a synergistic interaction between Au and MnO x is demonstrated. Whereas exposure to dry air (or oxygen) causes the conductivity of Pt/SnO 2 to decrease, the Au/MnO x and MnO x specimens continue to exhibit positive changes in surface conductivity. This is believed to be due to sufficiently high partial pressures of oxygen that transform the MnO x ‐based materials from n‐type semiconductors to p‐type. The surface analysis data implicate the importance 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 different with respect to Au/MnO x and Pt/SnO 2 . The potential advantages of combining Au/MnO x and Pt/SnO 2 into a single gas sensor are also considered. © 1998 John Wiley & Sons, Ltd.