An Investigation of the Gas Sensing Properties of a Novel Manganese-Oxide-Supported Gold CatalystEPA Grant Number: R823130
Title: An Investigation of the Gas Sensing Properties of a Novel Manganese-Oxide-Supported Gold Catalyst
Investigators: Gardner, Steven D.
Institution: Mississippi State University - Main Campus
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1995 through September 30, 1997 (Extended to September 30, 1998)
Project Amount: $98,580
RFA: Exploratory Research - Chemistry and Physics of Air (1995) RFA Text | Recipients Lists
Research Category: Air , Engineering and Environmental Chemistry
Description:The CO gas sensing performance of a novel manganese-oxide-supported gold catalyst (Au/MnO2) will be evaluated and subsequently correlated to the surface composition. Numerous different Au/MnO2 specimens will be prepared (0 at % to 20 at % Au) and the corresponding surface conductivity will be monitored as a function of CO exposure conditions inside a controlled ultrahigh vacuum (UHV) environment. The experiments are designed in order to enable intermittent surface analysis via x-ray photoelectron spectroscopy (XPS), ion scattering spectroscopy (ISS) and Auger electron spectroscopy (AES) during the sequential CO exposures. Among the parameters to be investigated are the CO sensitivity, selectivity and response time as a function of the sensor temperature. These data will be correlated to the Au/MnO2 surface characteristics in order to identify the corresponding chemical composition, the chemical oxidation states and the interactions occurring between the surface species. The results should provide considerable insight into the key molecular processes composing the gas sensing mechanism and hence aid in the systematic engineering of optimized sensors for specific applications.
The rationale for the investigation is based upon the remarkable CO oxidation activity of Au/MnO2 (only recently discovered) and how the catalytic properties of semiconducting metal oxides are ultimately related to the gas sensing characteristics (as assessed through surface conductivity measurements). Experimental data are reviewed indicating that effective CO oxidation catalysts do indeed exhibit pronounced changes in surface conductivity upon CO exposure and that the extent of conductivity change is proportional to the catalytic activity. Therefore, it is expected that Au/MnO2 will exhibit tremendous potential as a low-cost CO gas sensor. This assertion is further supported by data attesting that Au/MnO2 is significantly more active toward low-temperature ( 200 oC) CO oxidation than Pt/SnO2 and Pd/SnO2, the latter of which constitute two of the most intensely studied and widely utilized CO gas sensing materials. When the data are collectively considered, Au/MnO2 promises exceptional CO gas sensor performance at moderate operating temperatures (i.e., low power consumption) with excellent long-term stability!