Spectroscopic and Microscopic Investigations of Solid Oxide Fuel Cell Cathodes
EMSL Project ID
48741
Abstract
Solid Oxide Fuel Cells (SOFCs) are energy conversion devices that convert chemical energy to electricity directly at high efficiencies and thus are being studied intensively for environmentally friendly distributed power generation applications. As in any electrochemical device, polarization losses that occur at the electrodes account for significant performance losses in SOFCs. Presently there is a concerted effort to decrease the operating temperature of the cell from 1000oC, down to below 800oC. In doing so, the polarization losses at the cathode become performance limiting. Of particular interest are the electrocatalytic processes that occur at the surface and in the sub-surface layers of the cathodes. In the last few years, our group has focused on bringing hard and soft x-ray spectroscopic tools to bear on the compositional and structural changes that occur at the gas-cathode interface to better understand the role of these changes to the oxygen reduction process which are rate determining. These changes are best studied using clean, model, epitaxial thin films deposited on suitable single crystal substrates. It is conjectured that the presence of CO2 in the atmosphere might also play an important role in this segregation phenomenon because of its contribution to formation of SrCO3. In the anode gas recycle (AGR) SOFC, the exhaust gas contains as high as 30% CO2 produced by hydrocarbon fuels. In this case, any gas leakage from the anode side resulting from crack formation in the seals, electrolyte or interconnects will risk exposing the cathode to much higher CO2 concentration (up to 30%) compared with that in air (~400 ppm). In general, the new phases containing SrO and SrCO3 formed on the surface as a result of Sr surface segregation are considered detrimental to the performance of SOFCs due to their insulating nature and that their presence might block the available sites where oxygen reduction reaction takes place. Pulsed laser deposition (PLD) provides a convenient method to grow such thin films.
Project Details
Project type
Limited Scope
Start Date
2015-01-26
End Date
2015-03-28
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
Yu Y, AY Nikiforov, TC Kaspar, JC Woicik, KF Ludwig, S Gopalan, UB Pal, and SN Basu. 2016. "Chemical characterization of surface precipitates in La0. 7Sr0. 3Co0. 2Fe0. 8O3-? as cathode material for solid oxide fuel cells." Journal of Power Sources 333:247-253. doi:10.1016/j.jpowsour.2016.09.166
Yu Y, KF Ludwig, JC Woicik, S Gopalan, UB Pal, TC Kaspar, and SN Basu. 2016. "Effect of Sr Content and Strain on Sr Surface Segregation of La1-xSrxCo0. 2Fe0. 8O3-delta as Cathode Material for Solid Oxide Fuel Cells." ACS Applied Materials & Interfaces 8(40):26704-26711. doi:10.1021/acsami.6b07118