Exploration of Electronic and Catalytic Behavior in Epitaxial Complex Oxide Films and Nanocomposites

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Non-Technical Abstract:Thin films of metal oxides have long been studied for their various unique physical properties. It is only in the past few years, however, that research exploring oxide thin films for practical applications has emerged. Many of these materials exhibit excellent chemical performance, rivaling that of expensive precious metals such as platinum and iridium. This is particularly true for reactions that are relevant to fuel cells: the oxygen evolution and oxygen reduction reactions, which are both necessary for fuel cell technology. Various oxides have been shown to perform well in one reaction or the other, but few, if any, individual materials match the performance of platinum in both reactions. This project focuses on the synthesis of a composite material that combines two distinct types of oxides into a single surface so that their combined behavior can lead to catalytic performance that matches or exceeds precious metals. The research is integrated with outreach activities to encourage middle and high school students to pursue careers in science, math, and technology through participation in the Auburn University Summer Science Institute and Destination STEM. Through these programs, the PIs will perform demonstrations and lead group activities for students in rural and underserved areas of Alabama to broaden their exposure to science. Technical Abstract:Complex oxide thin films have been studied for many years for their wide array of properties, including ferromagnetism, ferroelectricity, and superconductivity. The development of metal oxide materials for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) electrocatalysis is directly relevant to fuel cell technologies. In this project the investigators perform systematic synthetic studies of transition metal oxides using molecular beam epitaxy to generate epitaxial matrix-pillar nanocomposite thin films where the perovskite oxide matrix phase is a strong OER catalyst and the spinel oxide pillar phase targets ORR. The work is delineated into three tasks: synthesis of perovskite and spinel powders, epitaxial thin films, and nanocomposites; spectroscopic and electrochemical characterization of electronic structure and band alignment, including ambient-pressure x-ray photoelectron spectroscopy studies; and preliminary electrocatalytic studies of uniform thin films and nanocomposites. These studies address fundamental materials chemistry and surface science questions as they relate to improving the performance and economic viability of transition metal oxide hybrid bifunctional materials. The project also provides educational experiences for undergraduate students to learn about materials characterization and for graduate students to perform state-of-the-art experiments at national user facilities.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.