Characterizing and Exploiting the Remarkable Surface Redox Chemistry of Ceria and Its Derivatives

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NON-TECHNICAL DESCRIPTION: The goal of this research to advance the fundamental understanding of the behavior of the surfaces of ceria (CeO2), a technologically relevant material for a wide range of industrial processes and devices. These applications include solid oxide fuel cells, electrolyzers for water splitting, solar-driven thermochemical fuel production, chemical looping combustion, automotive 3-way catalysts, photodegradation of organic pollutants, and supercapacitors. The approach underway in this project combines preparation of materials with well-defined surface termination with advanced characterization tools. The insights gained enable deliberate engineering of structures and selection of appropriate chemistries to achieve exceptional performance. Students at multiple levels are incorporated into the research and training goals of this effort via internships for high school and undergraduate students, as well as doctoral research opportunities for graduate students.TECHNICAL DETAILS: This research aims to dramatically advance the understanding of the surface properties of ceria and its solid solutions. The PI proposes to acquire fundamental knowledge about the redox chemistry of both internal and exposed ceria surfaces using well-defined structures that support exquisite studies by sophisticated characterization techniques. Efforts include A.C. impedance spectroscopy of thin-film materials to determine surface activity as a function of termination, cation chemistry, and strain; angle-resolved X-ray adsorption spectroscopy studies of such films to determine both Ce oxidation state and local chemical environment about cation species; impedance studies of individually defined grain boundaries prepared by fusing film-on-substrate structures; and creation and manipulation of vertically aligned nanostructures, with potential memristive properties, via substrate modification. The research leverages the extensive growth and characterization tools available on campus. Students are engaged at multiple levels. Graduate students participate in all aspects of this research and develop mentorship skills by advising undergraduate students in summer research and senior thesis research. Furthermore, high school students participate in laboratory activities through the Northwestern Academy, a collaboration between Northwestern University and Evanston Township High.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.