CAREER: Dynamics of Interfaces in Electrochemical Ceramic Systems

<p>NON-TECHNICAL DESCRIPTION: Solid Oxide Fuel Cell (SOFC) technologies offer a means of minimizing emissions and increasing efficiency associated with electricity production from a variety of fossil fuels. The impact of successful development and commercialization of SOFC systems would fundamentally change future power generation. However, it remains a major challenge to develop electrochemical ceramic systems that offer high performance with long-term stability. SOFC systems are constructed of multiple materials in distinct layers. During operation, chemical and structural changes at the interfaces between these layers can lead to performance losses. This project uses coupled electrochemical measurements and microscopy/spectroscopy at the nanoscale to understand how different material interfaces evolve under SOFC operational conditions, such that more efficient and more durable material combinations can be designed. Over the course of this project, undergraduate students from the NSF California Alliance for Minority Participation (CAMP) program, an NSF REU program, and other undergraduate research programs will be involved in academic year and summer research activities (10-15 students during the project). In addition, high school teachers from three high-need southern California school districts will be engaged in summer research and curriculum development projects. The teacher-researcher program is a key factor in outreach to high school students, impacting ~150 students by the end of the project, introducing them to the materials science discipline and encouraging more students to enter into science and engineering careers that will address our nations future energy needs. TECHNICAL DETAILS: The overarching objective is to develop an improved understanding of the interplay between mechanisms that govern performance in high-temperature electrochemical systems, and microstructural instabilities that lead to performance losses over time. The effort couples high-resolution imaging and microanalysis with traditional linear and emerging non-linear electrochemical test methodologies to better understand the links between the mixed ionic and electronic conduction (MIEC) characteristics of constituent materials, defect chemistry, microstructure, test/exposure conditions, and relevant electronic and ionic transport mechanisms. A primary focus is the systematic investigation of the electrochemical behavior of different classes of cathode materials that, despite spanning a wide range of relative electronic and ionic conductivities, show positive attributes as SOFC cathodes. Comparative testing of target materials sets, in symmetric and full cell test configurations, is used to discriminate between rate-controlling interfacial processes, thereby elucidating mechanisms that control the stability of key interfacial regions, and correlating these behaviors with the intrinsic electrode material properties using models of electrode mechanisms. Energy-filtered transmission electron microscopy and focused ion beam (FIB) techniques allow direct correlation of materials evolution (interface and surface chemistry and microstructure), electrochemical measurements, and intrinsic constituent material properties - at length scales relevant to the controlling mechanisms. Comparison of interfaces subjected to electric potential with regions that are disconnected from the electroded regions (using FIB techniques) is used to identify synergistic effects of electric fields, current density and exposure conditions on degradation processes. A mechanism-based model of these correlations is being developed to enable design of improved materials sets, and guide optimal development of a wide range of technologically important high temperature electrochemical devices. The graduate and undergraduate researchers will make fundamental contributions to the understanding of mixed conducting ceramics as electrochemical system electrodes, and be trained in cutting-edge research techniques critical to supporting future energy system development. </p>