In situ Raman spectroscopy and linear sweep voltammetry were used to characterize graphite formation on Ni/YSZ cermet anodes in solid oxide fuel cells (SOFCs) operating at 715 °C. The membrane electrode assemblies were run continuously with Ar-diluted H 2 and exposed to intermittent bursts of hydrocarbons. The appearance and disappearance of carbon deposits was monitored as a function of cell potential and hydrocarbon fuel identity. The hydrocarbon fuels employed in these studies included methane, ethylene, and propylene. Kinetic modeling predicts that of these three fuels, propylene is the most reactive under the conditions of the SOFC experiments. Methane was predicted to be virtually unreactive in the gas phase. Limited exposure of the SOFC anode to methane led to no observable carbon deposits and no appreciable change in SOFC electrochemical performance. Extended exposure to a continuous methane feed resulted in the formation of highly ordered graphite as evidenced by a single feature (assigned as the "G" band) at 1585 cm -1 in the Raman spectrum. The addition of ethylene to the incident fuel leads initially to the formation of highly ordered graphite as evidenced by the rapid growth of the G band and a small "D" band (at 1365 cm -1 ) in the Raman spectrum. 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 of tetrahedrally coordinated carbon, and SOFC performance suffered reversible degradation. Applying an overpotential to the anode led to the disappearance of carbon deposits with the intensity of the D band diminishing more rapidly than the G band. The disappearance rates depended directly on the anode overpotential.

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An apparatus for the study of solution phase kinetics using FT-IR spectroscopy has been developed. The observation chamber consists of an integrated tangential mixer-flow cell and a ZnSe element permitting attenuated total reflectance (ATR) measurements. The short optical pathlength afforded by ATR allows mid-IR observation of chemical reactions in aqueous solution, including the spectral region near the water bending vibration (1640 cm−1). High hydraulic backpressures required to force solution rapidly through a thin layer flow cell are not necessary with the ATR flow cell because the optical pathlength and the flow cross-section have been decoupled, allowing for a relativity large flow chamber when compared with instruments incorporating a transmission flow cell. Overall system performance has been evaluated using the hydrolysis of methylchloroacetate as a test reaction. The feasibility of observing reactions with initial half-lives of approximately 250 ms is demonstrated. The system is very robust, with little risk of damaging the optics during routine maintenance.

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