Structure, Reactivity and Transport at Surfaces and Interfaces of Doped Ceria Electrolytes and Cermets: An In Situ Atomic Resolution Investigation

Arizona State University, Scottsdale AZ

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: Developing efficient methods for generating electricity is a critical goal as society moves towards sustainable energy. Solid oxide fuel cells are a promising approach for efficiently converting the energy stored in chemical fuels directly to electricity. These ceramic cells run at high temperatures and can utilize a wide range of fuels such as natural gas, biofuels and gasoline. This fuel flexibility is a significant advantage of solid oxide fuel cells compared to other fuel cell technologies. Unfortunately, these devices are expensive and do not show long term stability because of their high operating temperatures. Many of these issues may be solved by developing new materials that would allow reliable operation of the solid oxide fuel cell at lower temperatures. Development of novel materials requires information on the behavior of materials under the harsh conditions present in a fuel cell. This project utilizes a powerful technique, electron microscopy which enables direct observation of atomic level changes taking place in materials under conditions similar to those present in a real fuel cell. This information provides a fundamental understanding of how the structural re-arrangements result in positive or negative materials functionalities. In turn, this information is being used to help in the design of new materials for improved fuel cell performance. Graduate, undergraduate and high school students are involved in this research. These research activities help them to understand how materials research can be employed to address important societal problems like the development of sustainable energy technologies. TECHNICAL DETAILS: Ionic transport properties and chemical reactivity are key factors impacting solid oxide fuel cell technologies. Cost and long-term stability problems associated with high temperature operation are unresolved materials design challenges. These issues have motivated the development of so-called intermediate temperature solid oxide fuel cells which employ novel materials that can deliver high ionic conductivity and catalytic activity at lower temperatures (500 - 700 C). Doped cerias are nonstoichiometric rare earth oxides which show high ionic conductivity and desirable catalytic properties making them potential candidates for use in intermediate temperature applications. However, there are important unresolved scientific questions related to interactions across grain boundaries in electrolytes as well as ceramic-metal and solid-gas interfaces in anodes. This project addresses these questions by using in situ aberration corrected electron microscopy along with monochromated electron energy-loss spectroscopy to develop a fundamental atomic level understanding of these interfacial processes. The nanoscale structures and chemistries affecting ionic conductivity and the reactivity in electrolytes and anode cermets are being determined. A new experimental approach is being developed to allow in situ atomic resolution observations of electroceramics under electrochemical conditions. This research is potentially transformative because it is providing new information on the dynamic processes relating structure and chemistry with electrochemical and electroceramic functionalities. This research project is training graduate and undergraduate students to learn about and contribute to the developments in energy-related oxide materials.