This thesis presents several studies on the performance and stability of solid oxide fuel cell (SOFC) anodes operating in natural gas and coal gas. It also presents a novel approach for high efficiency electrical energy storage with a methane/air solid oxide cell.
In Ni- 8mole%Y2O3 stabilized ZrO2 (YSZ) anode-supported cells, the addition of inert, anode-side porous barrier layers (3mole%Y2O3 stabilized ZrO2) was critical to eliminate coke formation in natural gas and air mixtures. An electronically-conducting oxide cell support was also found to be an effective barrier layer. In this case, porous Sr0.8La0.2TiO3 supported cells with Ni-YSZ functional layers were fabricated and studied for operation on natural gas. Stable, coke-free operation was achieved at 800°C for a current as low as 0.2 Acm-2.
Strontium doped lanthanum chromites mixed with Gd0.1Ce 0.9O2-d (GDC) were evaluated as composite anodes. LaSr 2Fe2CrO3-d (LSFeCr), a mixed ionic and electronic conducting oxide, was evaluated for operation on a surrogate coal syngas and CO-H2 fuel mixtures. La0.8Sr0.2Cr0.82 Ru0.18O3-d (LSCrRu) and Pd-substituted (La,Sr)CrO 3-d, which precipitate Ru and Pd nanoparticles respectively during operation, were also studied. The LSCrRu -GDC anode was characterized in coal syngas and fuel mixtures containing H2, CO, CO2 and H 2O. The anode was less prone to coking than Ni-YSZ anodes. The Pd-substituted (La,Sr)CrO3-d-GDC anode was characterized in H2 fuel and exhibited a unique regenerative behavior: redox cycles were found to disperse and re-nucleate the Pd nanoparticles.
Finally, a novel approach is presented for using a solid oxide cell for scalable electrical energy storage with a high round-trip efficiency. Operation at a reduced temperature (∼ 600°C) and/or an increased pressure (∼10 atm) yields a storage chemistry where H2O and CO2 are electrolyzed to a CH4-rich gas. The CH 4-forming electrolysis reactions are less endothermic than H2 and CO forming reactions, allowing for a lower electrolysis voltage and hence improved round-trip efficiency.
|Advisor:||Barnett, Scott A.|
|Commitee:||Faber, Katherine, Mason, Thomas, Poeppelmeier, Kenneth|
|Department:||Materials Science and Engineering|
|School Location:||United States -- Illinois|
|Source:||DAI-B 72/08, Dissertation Abstracts International|
|Subjects:||Chemical engineering, Energy, Materials science|
|Keywords:||Anode, Chromite, Energy storage, Fuel cells, Nickel-ysz, Solid oxide fuel cells|
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