Tuning Surface Chemistry through Polarization

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In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Prof. Eric I. Altman of Yale University will investigate the fundamentals of how polarization in oxides can be used to manipulate surface chemical and catalytic properties. The overall program objective is to understand how polar interfaces can be exploited to induce new surface chemistry, and to create materials whose surface chemistry can be dramatically altered by switching the polarization direction of a ferroelectric support. This understanding is essential to developing new methods to tune catalytic activity for demanding reactions, to create new classes of materials that allow surface reactions to be turned on and off, and to create materials whose surface properties can be reversibly altered and patterned. The objective is met through three complementary thrusts that all exploit the dramatic polarization-direction dependent properties of ZnO(0001). The first thrust focuses on the ability to induce polarization-dependent properties in catalytically important oxides that are non-polar; the Cr2O3/ZnO (0001) system will be studied as a prototypical system anticipated to give the largest polarization dependence possible. The second thrust is directed towards inducing switchable surface properties in a material that in bulk form is polar but not ferroelectric. In this case Professor Altman and his students aim to induce ferroelectricity in ZnO by supporting it as an ultra-thin layer on a ferroelectric support. The third thrust focuses on new ferroelectric materials in which the constituent oxides have similar reducibilities and are both chemically active; ZnSnO3 will be studied as a model for this new class of materials. The proposed work relies on atomically precise fabrication tools and characterization methods to determine the intrinsic surface chemical properties of well-defined surfaces, and collaboration with first principles theory to understand the mechanisms responsible for the observed behavior. The project will have a broad impact through its contributions to education and training in emerging areas of science and technology. The graduate and undergraduate students working on this project will get a unique opportunity to develop new strategies for tuning reactivity. To meet these objectives the students will develop expertise in fields spanning surface science, materials science, kinetics and dynamics and spectroscopy in a collaborative environment integrating experiment and theory and international experiences. In addition, international partnerships will allow students from overseas to contribute to the project and for Yale students to travel abroad; as research is now an international endeavor, these partnerships provide valuable international connections and exposure to international cultures that greatly benefit the students' future careers.