SOEC efficiency and cost improvement Part 1 and 2.

Yildiz, B. ; Chang, K.-C. ; Meyers, D. J. ; You, H. ; Carter, J. D. ; Elam, J. W. ; Honegger, D. A. ; Libera, J. A. ; Pellin, M. J.

Argonne National Laboratory

关键词: 30 Direct Energy Conversion;    Advanced Photon Source;    Lanthanum;    Electrolysis;    08 Hydrogen;   

DOI  :  10.2172/947082
RP-ID  :  ANL-07/20
RP-ID  :  DE-AC02-06CH11357
RP-ID  :  947082

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来源: UNT Digital Library

【 摘 要 】

Part I: Electrochemical and X-ray Characterization of Solid-Oxide Electrolysis Cell Oxygen Electrodes on Electrolyte Substrates--The governing reaction mechanisms, and the electrode and electrolyte material compositions and structures, that controls the efficiency and durability of the solid oxide electrolysis cells (SOEC) need to be identified and well-understood for a significant improvement in nuclear hydrogen production using high temperature steam electrolysis. ANL conducted experimental analysis of SOEC electrolyte and electrodes to progress in this objective. Our study on the oxygen electrode focused on specifically the effect of electrode crystal structure on its electrochemical performance, and the evolution of the electronic and structural properties of the electrodes while under electrochemical conditions and high temperature. We found through electrochemical impedance spectroscopy experiments that, while different crystal orientations in La{sub 0.8}Sr{sub 0.2}MnO{sub 3+d} (LSM) show different initial performance and different electrochemical activation under SOEC conditions, a good mixed ionic electronic conductor La{sub 0.8}Sr{sub 0.2}CoO{sub 3+d} (LSC) does not seem to exhibit similar variations. Our in-situ x-ray and electrochemical measurements at the Advanced Photon Source of ANL have identified the chemical states of the A-site elements of the doped lanthanum manganite electrodes. We found that the changes in the concentration and in the electronic state of the La and Sr (the A-site elements of the perovskite) occurring only at the top airelectrode film interface can be responsible from the electrochemical improvement of the SOEC anode under DC current. Our observation related to the La chemical state change is unexpected and probably unique to the electrochemical current-conditioning. Part II: Progress Towards the Atomic Layer Deposition of Lanthanum Strontium Manganate--Lanthanum strontium manganate (LSM) is the most commonly used cathode material for solid oxide fuel cells (SOFC) and also solid oxide electrolysis cells (SOEC) for hydrogen production through steam electrolysis. The ability to deposit LSM in the form of thin, conformal films onto high surface area support materials will enable the development of more efficient SOFC and SOEC devices. Moreover, thin, uniform LSM films prepared on flat surfaces are ideal for performing synchrotron X-ray experiments aimed at understanding the materials issues that control SOEC performance. Atomic layer deposition (ALD) is a very effective technology for fabricating thin, conformal films on flat surfaces as well as high surface area supports. In this study, we describe our work developing ALD methods for depositing La{sub 2}O{sub 3}, MnO{sub 2}, and mixtures of these oxides using cyclopentadienyl precursors. We have utilized in situ quartz crystal microbalance (QCM) measurements to explore the range of conditions for growth of these materials as well as to determine the appropriate oxygen sources. In addition, thin films of La{sub 2}O{sub 3} and MnO{sub 2} were deposited on Si(100) substrates and analyzed using spectroscopic ellipsometry to determine the refractive index and growth rates of these materials. Finally, mixed-oxide films La{sub 2}O{sub 3} and MnO{sub 2} were prepared and analyzed with X-ray fluorescence to determine the composition of the films.