Project Title: GOALI: Sinter-Resistant, Self-Regenerating Platinum Group Metal Catalysts for Automotive Exhaust Treatment
Advanced combustion engines being developed for meeting our transportation needs achieve improved fuel efficiency by lowering exhaust temperatures. This puts demands on the technology for catalytic converters, since these catalysts must become active at lower temperatures. The proposed research addresses the design of these catalysts, leading to improvements in air quality and to societal needs for energy. Automotive exhaust catalysts lose activity during use due to precious metal sintering. This loss of performance requires a new exhaust catalyst, thereby putting pressure on prices for precious metals such as Pt and Pd. By developing ways to slow the growth of metal particle size, demand for these precious metals is reduced, and they can be used more efficiently. This GOALI award recognizes the strategic importance of this research to the U.S., and is in support of an industry-university collaboration between Abhaya Datye of the University of New Mexico and Chang Kim and Gongshin Qi of General Motors Global R&D. The university participants will use model catalysts that allow characterization with advanced microscopy techniques which cannot be applied to actual commercial automotive catalysts. The results will be shared with the scientists at GM, and the team will attempt to implement the findings in new technologies for exhaust emissions control. An added educational feature is that students will spend time working in the industry partner laboratories as part of this collaborative research program.
The research challenge being addressed here impacts the entire class of precious metal heterogeneous catalysts used for meeting the needs for energy, materials and fuels. Three way catalysts in automotive exhaust (especially those in the close coupled position) are subjected to elevated temperatures that lead to growth of nanoparticle size and loss of activity. The research will address Ostwald ripening of nanoparticles, investigating the key steps of atom emission and capture, by using model catalysts. Industrial supported metal catalysts do not lend themselves to direct measurements of processes such as atom emission or capture, which are critical to understanding catalyst sintering. This research program uses novel forms of model catalysts that can be heated to temperatures and gas atmospheres encountered in automotive exhaust. The model catalysts allow obtaining time-lapsed electron micrographic images of the same region of the sample, so that rates of atom transport can be inferred. These rates, coupled with a robust physics-based model, will help improve predictions of catalyst sintering. Methods will be developed to modify the rates of emission and novel approaches developed to capture mobile species. Concepts developed using model catalysts will be translated to powder catalysts and tested under realistic conditions using the facilities of the industry partner. The close participation of industry and university researchers is critical for validating the concepts and models. GM has committed significant resources in terms of people time and access to facilities, to enable this research to be successful. The partnership will help address significant unknowns in the understanding of catalyst sintering, and will lead to advances in the synthesis of novel catalysts with improved reactivity.
