Date of Graduation

2015

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

John W Zondlo

Committee Co-Chair

Edward M Sabolsky

Committee Member

Charter D Stinespring

Abstract

The objective of this work was to investigate how fuel utilization and method of fuel delivery for a large planar fuel cell with co-flow configuration will affect the degradation rate and mechanism of phosphine poisoning of a solid-oxide fuel cell (SOFC). Coal syngas, a potential fuel source for SOFCs, contains gas phase impurities such as PH3, which rapidly degrade Ni-based SOFC anodes. Researchers have shown significant reconstruction of Ni-anodes in button cell configurations with ~0.5 mV hr-1 degradation rates, but it is not evident that these rates will occur in actual stack applications. A singular planar stack repeat unit was constructed using a Haynes 242 interconnect manifold with a cobalt-oxide coating. The cell was operated at 800°C with 10 ppm PH3 in dry H2. Cell performance was evaluated over 500 hours by means of voltage-current measurements and impedance spectroscopy. PH3 was measured entering the fuel cell and then exiting the fuel cell in the exhaust. The post-run material analysis of the contaminated cell was conducted via x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron micrographs (SEM). In this work, there was no appreciable degradation attributable to PH3 poisoning of the anode. No reconstruction of the Ni-anode was observed. This result is in contrast to the many papers published on the subject, where anode-supported SOFC in a button cell configuration degraded rapidly. It is believed that the increased fuel utilization of the large planar cell compared to the published literature using button cells contributed to increased H2O generation which led to side reactions that prevented the phosphorus from interacting with the Ni-anode; platinum components may have catalyzed these reactions.

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