The Strong-Metal Support Interaction: Insights from Molecular Theories and Experiments

Purdue University, West Lafayette IN

Investigators

Abstract

Catalysts play an essential 'behind-the-scenes' role in many aspects of modern society. For example, catalysts lower the energy loss of producing high performance gasoline from crude oil. In the production of plastics, catalysts selectively lead chemical reactions down a certain pathway to produce desired products. The number of potential pathways in catalytic reactions is large, and the catalyst structure itself may change significantly during the reactions. Due to this complexity, molecular-level aspects of many phenomena in catalysis have not been fully elucidated. Despite being discovered nearly thirty years ago, the strong metal-support interaction (SMSI) is one such phenomenon that remains poorly understood at a molecular level. SMSI refers to the strong interaction between a catalytic metal nanoparticle and an oxide support, to which the metal is anchored. Under reaction conditions that are relatively common, a portion of the oxide support may actually form a film that partially covers the catalytic nanoparticle. This film can either promote or inhibit catalytic processes, depending upon the particular catalytic materials involved, and a general strategy to understand and control its properties does not exist. The central goal of this project is, therefore, to unravel the molecular science of how the different components of these catalyst systems work together to enhance catalyst performance. To use SMSI to promote catalysis by leveraging molecular-level insights, this project will combine periodic Density Functional Theory calculations with surface science experiments and measurements on model nanoparticles to study trends in the structure, energetics, and electronic properties of ultrathin (hydroxy)oxide films on transition metal substrates. Rigorous models of the films' structures as a function of ambient pressures and temperatures will be developed. The predictions will be performed on single crystal substrate models, and will be refined against a series of ultrahigh vacuum surface science experiments. The trends that emerge from these combined theoretical and experimental studies will then be validated on nanoparticle models. It is anticipated the project will provide a wealth of information about ultrathin (hydroxy)oxide/metal interfaces and will suggest new strategies for controlling and exploiting the SMSI. This fundamental knowledge may, in turn, lead to the development of robust catalysts for energy and health applications. The work will be carried out by two graduate students who will be trained in state-of-the-art techniques in theoretical and experimental catalysis. The students will be assisted by high school interns from economically disadvantaged backgrounds who will also be exposed to these forefront scientific methods. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.