Metal Encapsulation Strategies to Optimize and Minimize PGE Use in Heterogeneous Catalysts

The goal of this project is to reduce the amount of platinum-group elements (PGEs) in heterogeneous catalysts used in catalytic converters in automobiles. Catalytic converters account for 33% of the world's Pt use, 85% of Pd, and 90% of Rh, and an improvement in their utilization would directly lead to a crucial decrease in our dependency on these rare and expensive metals. PGEs usage is about 400 tonnes/year, and since the automotive industry accounts for more than half of the need, an improvement in the stability for automotive emission catalysts would cut the demand of PGEs. Therefore, this project has the potential to lead to the saving of hundreds of tonnes of PGEs per year, with consequential effects on the many aspects of PGE mining and its applications. The reason for using larger amounts of Pt, Pd and Rh than necessary in catalytic converters is due to their unstable nature at high temperatures in the exhaust gas mixture, which leads to their sintering and loss of activity. Our preliminary work demonstrates an approach where Pt/Pd catalysts are active and stable under air and steam conditions above 1,000 °C. These preliminary results prompt us to investigate and understand the reasons for such unprecedented stability, as well as how to further improve these catalysts through a theory-driven approach supported by detailed operando characterization and precise synthesis. Overall, the project vision is to understand the catalytic activity and stability of PGE-containing materials and ultimately significantly improve their efficiency and reduce their usage by more than 50%. This project details fundamental science that will be developed to contribute to the DOE's mission of producing science, technology and engineering solutions for re-establishing U.S. competitiveness in the use of critical precious elements. This project is also in line with the goals of developing hypothesis-driven research towards synthesis approaches that result in reduced and optimized use of PGEs in the technology that uses the most of these precious metals, namely, automotive emission control systems.