Structure-Function Relationships for Early Transition Metal Carbide and Nitride Cataysts

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0933239 Thompson Early transition metal (Group IV-VI) carbides and nitrides are a fascinating class of materials with a broad range of potential applications including use as catalysts for energy and environmentally sustainable processes. These relatively low cost materials can be produced in nanoscale form with surface areas as high as 200 m2/gr, have been demonstrated to be active for a number of industrially significant reactions including water gas shift and alkane isomerization, and are thermally and chemically stable. The design of nanoscale early transition metal carbide- and nitride-based catalysts would benefit significantly from a better understanding of relationships between their structural, compositional and functional properties. The goal of this research is to elucidate key structural and compositional features that govern the catalytic properties of early transition metal carbides and nitrides using two commercially relevant test reactions, the water gas shift (WGS) and Fischer-Tropsch Synthesis (FTS). The principal techniques that will be employed to accomplish the project goal are ultrahigh resolution transmission electron microscopy (TEM) and in situ x-ray absorption spectroscopy (XAS). The TEM and XAS results will be complemented by results from infrared spectroscopy and x-ray photoelectron spectroscopy. This effort is responsive to the Catalysis and Biocatalysis Program goal of supporting multidisciplinary research on the synthesis and characterization of catalysts that function at the nanoscale. Potential applications for nanoscale carbide- and nitride-based catalysts include the production of hydrogen and "green gasoline" via FTS, and consequently the project supports efforts related to energy diversity and reductions in greenhouse gas emissions. The intellectual merit of the proposed research lies in a significant expansion of the knowledge base for early transition metal carbide and nitride catalysts. While the database of reactions catalyzed by these materials has grown, there is little fundamental information about relationships between their structure, composition and function. The ultrahigh resolution TEM will allow, perhaps for the first time, high resolution imaging of the non-metal atoms in the metal atom matrix of the catalyst. In addition, XAS, one of only a few in situ methods, will provide the type of compositional, structural and electronic information needed to develop unambiguous correlations. Relationships derived during the proposed research will significantly enhance our fundamental understanding of the character of carbides and nitrides, and could facilitate their design and development as catalysts and catalyst supports for the sustainable production of a variety of chemicals and fuels. With regard to the broader impacts, the proposed research will engage under-represented minority high school, undergraduate and graduate students in socially relevant research. The proposed project will leverage on-going education and outreach activities including the Michigan-Louis Stokes Alliance for Minority Participation and Undergraduate Research Opportunity Program. Through an expansion of the University of Michigan Chemical Sciences at the Interface of Education (CSIE) program, undergraduate and post-doctoral chemical engineering and materials science students will be able to add education to their professional studies. In addition, through a collaboration with the IDEA Institute, teachers from the Detroit and Ypsilanti School Districts, both of which have large populations of underserved students, will be engaged in summer camp programs focused on microscopy and surface science. Researchers engaged in the proposed project have long-standing commitments to increasing the participation of underrepresented groups in authentic research and integrating research into educational activities.