Hydrocarbon Fuels in Solid Oxide Fuel Cells: In Situ Raman Studies of Graphite Formation and Oxidation
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- 作者：Michael B. Pomfret ; Jonathan Marda ; Gregory S. Jackson ; Bryan W. Eichhorn ; Anthony M. Dean ; Robert A. Walker
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：April 3, 2008
- 年：2008
- 卷：112
- 期：13
- 页码：5232 - 5240
- 全文大小：333K
- 年卷期：v.112,no.13(April 3, 2008)
- ISSN：1932-7455
文摘
In situ Raman spectroscopy and linear sweep voltammetry were used to characterize graphite formation onNi/YSZ cermet anodes in solid oxide fuel cells (SOFCs) operating at 715 
C. The membrane electrodeassemblies were run continuously with Ar-diluted H2 and exposed to intermittent bursts of hydrocarbons.The appearance and disappearance of carbon deposits was monitored as a function of cell potential andhydrocarbon fuel identity. The hydrocarbon fuels employed in these studies included methane, ethylene, andpropylene. Kinetic modeling predicts that of these three fuels, propylene is the most reactive under the conditionsof the SOFC experiments. Methane was predicted to be virtually unreactive in the gas phase. Limited exposureof the SOFC anode to methane led to no observable carbon deposits and no appreciable change in SOFCelectrochemical performance. Extended exposure to a continuous methane feed resulted in the formation ofhighly ordered graphite as evidenced by a single feature (assigned as the "G" band) at 1585 cm-1 in theRaman spectrum. The addition of ethylene to the incident fuel leads initially to the formation of highly orderedgraphite as evidenced by the rapid growth of the G band and a small "D" band (at 1365 cm-1) in the Ramanspectrum. Subsequent additions of ethylene created more disorder and led to deteriorating SOFC performance.Small amounts of propylene added to the fuel feed formed disordered carbon having significant amounts oftetrahedrally coordinated carbon, and SOFC performance suffered reversible degradation. Applying anoverpotential to the anode led to the disappearance of carbon deposits with the intensity of the D banddiminishing more rapidly than the G band. The disappearance rates depended directly on the anodeoverpotential.
C. The membrane electrodeassemblies were run continuously with Ar-diluted H2 and exposed to intermittent bursts of hydrocarbons.The appearance and disappearance of carbon deposits was monitored as a function of cell potential andhydrocarbon fuel identity. The hydrocarbon fuels employed in these studies included methane, ethylene, andpropylene. Kinetic modeling predicts that of these three fuels, propylene is the most reactive under the conditionsof the SOFC experiments. Methane was predicted to be virtually unreactive in the gas phase. Limited exposureof the SOFC anode to methane led to no observable carbon deposits and no appreciable change in SOFCelectrochemical performance. Extended exposure to a continuous methane feed resulted in the formation ofhighly ordered graphite as evidenced by a single feature (assigned as the "G" band) at 1585 cm-1 in theRaman spectrum. The addition of ethylene to the incident fuel leads initially to the formation of highly orderedgraphite as evidenced by the rapid growth of the G band and a small "D" band (at 1365 cm-1) in the Ramanspectrum. Subsequent additions of ethylene created more disorder and led to deteriorating SOFC performance.Small amounts of propylene added to the fuel feed formed disordered carbon having significant amounts oftetrahedrally coordinated carbon, and SOFC performance suffered reversible degradation. Applying anoverpotential to the anode led to the disappearance of carbon deposits with the intensity of the D banddiminishing more rapidly than the G band. The disappearance rates depended directly on the anodeoverpotential.