Collaborative Research: Elucidating the Roles of Electric Fields Within Mixed Ionic and Electronic Conducting Oxides Under Electrochemical Reducing Conditions

NON-TECHNICAL DESCRIPTION: High temperature electrochemical devices are critical elements needed for new high efficiency energy conversion systems. For example, a solid oxide electrolysis cell can provide hydrogen via steam electrolysis. Alternatively, as envisioned in this work, such a system can also provide syngas (carbon monoxide and hydrogen) from steam and carbon dioxide. Such complex systems operate with high efficiency and can use electricity obtained from intermittent power sources. However, their performance requires proper optimization to avoid degradation. Recent work has shown that mixed ionic-electronic conducting oxide-based cathodes exhibit promising activity and stability, which facilitates the use of pure carbon dioxide in the feed. However, a fundamental understanding of how these oxides work for processing of carbon dioxide is still limited. In this project, PIs Nikolla and McEwen integrate experiments and theory to determine how a mixed ionic-electronic conducting ceramic material interacts with carbon dioxide to facilitate its processing. Design criteria for identification of robust (active and stable) oxide cathodes in a solid oxide electrolysis cell environment are being developed. PIs Nikolla and McEwen are also actively engaged in outreach activities through training graduate and undergraduate students, who typically find employment in industry or academia. The research team also partners with industry by interacting with the Toyota Research Center. As such, this research exposes students to an industrial research environment and enables them to see the link between fundamental work in academia and application in industry. TECHNICAL DETAILS: Experimental and theoretical techniques are combined to develop a fundamental understanding of the electrochemical reduction of CO2 on mixed ionic-electronic conducting (MIEC) oxides. This fundamental understanding then enables design criteria for identification of robust (active and stable) oxides as solid oxide electrolysis cell (SOEC) cathodes to be defined. SOECs are high temperature, solid-state electrolyzers characterized by high efficiencies and unique scalability. In this project, the heterogeneities in an oxide layer, which alter the local electric field at its surface and correlate to the performance of a SOEC, are examined and the effect of the composition on the reducibility of MIEC oxides is elucidated. This knowledge is used to define the design criteria for robust MIEC-cathode SOECs. Activities that enhance the education of the next generation of students, including a summer research exchange program among the two groups for students, and partnerships with the Toyota Research Center that expose students to an industrial research environment and provide a link between the fundamental work in academia and application in industry, ensure the broad impacts of this project. 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.