Properties, Electrochemical Activity, and Stability of 

Solid Oxide Cell Fuel-Electrode Materials 

Scott Barnett, Department of Materials Science, Northwestern University

The importance of reaching net-zero CO₂ emissions by 2050 is becoming increasingly clear.  Projected pathways for reaching net-zero envision extensive use of devices called Solid Oxide Cells – applications include electrolytic hydrogen production, electricity storage, and efficient fuel cell electrical generation.  Hydrogen will also be produced from biofuels with CO₂ sequestration; utilization of this resource using solid oxide cells has significant advantages including high electrical generation efficiency and maximal reduction of CO₂ emission.  

The present proposal focuses on fundamental studies of new materials that hold promise to improve solid oxide cell characteristics and long-term stability, thereby enhancing their ability to contribute towards carbon-neutral energy systems.  The focus of this proposed research is on the solid oxide cell’s fuel electrode, motivated by the significant challenges with the currently-used electrode materials.  Our previous studies under DOE-BES funding led to the discovery of a new class of fuel electrodes – oxide materials that exsolve performance-enhancing metallic nanoparticles during cell operation.  This project’s results show that these electrodes can provide better electrochemical performance and specific advantages compared with the incumbent electrodes.  

The proposed studies will yield an in-depth understanding of materials properties and the resulting electrode performance and stability, providing a basis for improved solid oxide cells.  Specific research directions include: (1) fundamental in situ studies to determine the pathways of nanoparticle exsolution and associated oxide phase transformations, under a range of different fuel conditions and reduction-oxidation cycling; (2) studies of oxide electronic transport properties including development of new higher-conductivity compositions; (3) studies of how electrode processes are affected by nanoparticle exsolution and associated oxide phase changes; (4) exploration of the stability of the electrodes relative to SOC electrolytes, with an aim towards developing novel thin-electrolyte cells; and (5) explore the factors determining the long-term performance stability of electrodes, including the effects of nanoparticle coarsening and reduction/oxidation cycles, as well as studies of degradation due to high-current electrolysis.