In Operando Vibrational Raman Studies of Chlorine Contamination in Solid Oxide Fuel Cells

Vibrational Raman spectroscopy coupled with voltammetry and impedance measurements was used to explore the effects of chlorine on solid oxide fuel cell (SOFC) performance and durability. Experiments described in this talk use newly developed vibrational Raman methods to acquire vibrational spectra from SOFC anodes exposed to CH₃Cl and CH_4.  SOFC anodes were exposed to 110 ppm dry CH₃Cl at 650°C for up to four hours while intermittently exposing the cell to methane for ten minute intervals. In these experiments Raman spectroscopy was used to monitor carbon accumulation kinetics and using a new optically accessible apparatus designed to fit on the stage of the Raman microscope. Electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) measurements performed under CH₄ following 1 hour of exposure to CH­₃Cl showed marked degradation.  This degradation was less apparent when the SOFC was operated with H₂ following exposure to CH₃Cl.  Under methane peak power reduced at a rate of 13.8% per hour in the presence of CH₃Cl. EIS with CH₄ following exposure to CH₃Cl showed a small increase of bulk resistance yet consistent polarization resistance (R_pol) until the end of the final exposure, when R_pol increased dramatically. Observable carbon accumulation during CH₃Cl exposure became less pronounced over time and eventually stopped accumulating at all suggesting that the primary effect of the Cl contaminant was deactivation of the Ni catalyst. Interestingly, these effects of Cl on SOFC performance with methane proved largely reversible as performance and carbon accumulation behavior recovered upon removal of the CH₃Cl.