Combustion of fossil fuels, essential for electricity generation and vehicular propulsion, is generally incomplete, leading to harmful NOx, CO, and unburned hydrocarbons emissions.  Great progress in minimizing such emissions has relied on the operation of “three-way catalysts” (TWCs), which utilize a combination of precious metals and metal oxides with the ability to take up or release oxygen for reduction/oxidation of pollutants (NOx to N₂ plus CO and HC to CO₂ and H₂O, respectively).  In this project, we are investigating the rate at which oxygen storage materials (OSM) exchange oxygen with the atmosphere and the magnitude of oxygen they store with the aid of geometrically well-defined thin film structures. Impedance spectroscopy, Kelvin probe, and thermogravimetric methods are used to determine electrochemical performance and oxygen storage capabilities.  These properties, when correlated to actual TWC performance using a differential flow reactor, will allow for a more detailed understanding of performance criteria.