MTL Annual Research Report 2012

Catalytic Oxygen Storage Materials

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 and CO and HC to CO₂ and H₂O, respectively) ^[1] . In this project, we are investigating the rate at which oxygen storage materials (OSM, typically Ce_xZr_1-xO_2-δ) 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, thermogravimetry, coulometric titration, and electrical conductivity measurement 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. Previous studies on Pr_xCe_1-xO₂in our group have demonstrated the feasibility of these methods ^{[2] [3] [4]} .

1. P. Forzatti, L. Castoldi, I. Nova, L. Lietti, and E. Tronconi, “NOx removal catalysis under lean conditions,” Catalysis Today, vol. 117, pp. 316-320, June 2006. [↩]
2. D. Chen, S. Bishop, and H. L. Tuller, “Praseodymium-cerium oxide thin film cathodes: Study of oxygen reduction reaction kinetics,” Journal of Electroceramics, vol. 28, pp. 62-69, Jan. 2012. [↩]
3. D. Chen, S. Bishop, and H. L. Tuller, “The chemical capacitance of praseodymium-cerium oxide thin films and relationship to nonstoichiometry,” under review. [↩]
4. S. R. Bishop, T. S. Stefanik, and H. L. Tuller, “Electrical conductivity and defect equilibria of Pr_0.1Ce_0.9O_2-δ,” Physical Chemistry Chemical Physics, vol. 13, pp. 10165-73, Apr. 2011. [↩]