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In situ vibrational Raman scattering has been employed to examine rates of carbon formation and removal from Ni/YSZ cermet anodes in functioning, electrolyte-supported solid oxide fuel cells (SOFCs). Specifically, Raman scattering characterized the ability of different gas phase species commonly used as reforming agents to remove carbon that had accumulated on Ni/ YSZ cermet anodes at 730 °C. Anodes held at open circuit voltage (OCV) were exposed first to a dry methane feed and then to an inert carrier gas containing either H 2 O (g) , CO 2 , or O 2 . Carbon deposits began to form within 5 s of methane exposure. Vibrational Raman spectra showed that the carbon deposits consisted of highly ordered graphite as evidenced by a single pronounced feature in the spectra at 1556 cm −1 . Changing the incident gas phase environment over the anode to Ar containing either H 2 O (2%), CO 2 (6%), or O 2 (6%) led to quantitative removal of the carbon and partial or complete oxidation of the Ni as evidenced by the growth of a NiO vibrational band (at 1080 cm −1 ) in the Raman spectra. Carbon removal rates from the Ni/YSZ anode were fastest with vapor phase H 2 O, then O 2 , and finally slowest with CO 2 . The extent of Ni oxidation was much more pronounced with O 2 than with either H 2 O or CO 2 . These chemical processes observed directly in the Raman spectra were reflected in the device's open circuit voltage (OCV). Correlating findings from these two methodsin situ Raman spectroscopy and voltage measurementsprovided a direct connection between the chemical composition of SOFC anodes and the electrochemical condition of the device. These results inspire confidence that any of the reforming agents usedH 2 O, O 2 , and CO 2 will remove carbon from Ni anodes quantitatively on a time scale of ∼10 to ∼125 s. However, H 2 O and CO 2 appear less likely to damage the cell following carbon removal, as H 2 O and CO 2 do not quantitatively oxidize the Ni in the cermet anode. In contrast, exposure to O 2 leads to much more extensive Ni oxidation and an OCV that approaches 0.0 V, implying that the Ni/NiO equilibrium sustained by H 2 O and CO 2 is driven completely to NiO by O 2 .

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