Systems where lean combustion processes are carried out in excess air offer significant fuel efficiency benefits that can contribute to reductions of greenhouse gas (GHG) emissions. However, an important byproduct of lean combustion is NOx (x = 1, 2). While cost-effective technologies have been demonstrated for the remediation of NOx produced at stationary sources, solutions for the aftertreatment of NOx produced by mobile sources including diesel powered vehicles remains a major challenge. One of the most significant aspects is that Platinum-containing catalysts are the most effective catalysts for this operation, and the amount of platinum required makes these catalysts prohibitively expensive. In this proposal which calls for collaboration between PIs Thompson from University of Michigan and Schneider from University of Notre Dame, an industrial partner, General Motors, is added to make it a GOALI proposal as well as a Collaborative one. The intent is to resolve why catalytic activity of about the same magnitude as platinum has been observed with a non-precious metal containing perovskite catalyst originally observed by General Motors scientists, and to determine if rugged, inexpensive catalysts can be demonstrated which could in fact replace platinum. This would be a significant change in our understanding of reactions that are catalyzed by platinum, and on a more practical level, would open up the area of diesel-powered vehicles with the improved efficiencies and reduced GHG emissions expected, as less-expensive catalytic after-treatments or mufflers could be available. The program involves the two universities and the industrial partner at many points of contact and in various phases of the work. Students will benefit from the collaboration and from the contact with industry. In addition the PIs will leverage existing education and outreach programs on the campuses to both interest and educate society about the issue and benefits from success in the project.
Nitrogen oxides are regulated emissions from vehicles because of their harmful impact on the environment. Current emissions control systems all rely on precious metals in some way or form to convert the nitrogen oxides into harmless materials. Much less expensive base metal oxides have been identified as potential replacements, but little is understood about how these oxides interact or transform the nitrogen oxides. In this collaborative project, we use molecular-level computer models to determine how and to what extent the nitrogen oxides interact with these materials. We use this information both to understand experiments carried out by our collaborators and to predict the behavior of materials not yet studied in the lab. In particular, we have been able to identify key characteristics of the oxides that promote the oxidation of NO to NO2, an important step in emissions control, and to understand how other components of the exhaust, in particular sulfur, interfere with this function. This work involved collaboration between two universities and an industry partner and engaged undergraduates, graduate students, and post-doctoral scholars in the research. The work was disseminated at regional and national meetings, is documented in two peer-reviewed publications, and will be further documented in a Ph.D. dissertation and associated publications.
