Comparing in Situ Carbon Tolerances of Sn-Infiltrated and BaO-Infiltrated Ni-YSZ Cermet Anodes in Solid Oxide Fuel Cells Exposed to Methane

Experiments performed in this work explored how Ni-YSZ cermet anodes infiltrated with 1% Sn or 1% BaO mitigate carbon formation compared to undoped Ni-YSZ anodes in functioning solid oxide fuel cells (SOFCs). In situ vibrational Raman spectroscopy was used to study the early stages of carbon accumulation on the SOFC anodes at 730 °C with methane and under open circuit voltage (OCV) conditions. Additionally, carbon removal with different gas phase reforming agents was evaluated. The effects of these phenomenacarbon accumulation from methane and carbon removal by reforming agentson the electrochemical capabilities of a device were monitored with electrochemical impedance and voltammetry measurements. Vibrational spectra showed that the undoped and 1% Sn infiltrated anodes were very susceptible to carbon formation from methane while considerably less carbon accumulated on the 1% BaO anodes. Electrochemical data, however, implied that carbon accumulated in different regions of the anode and that both Sn and BaO effectively reduced carbon accumulation but also inhibited electrochemical oxidation. For each anode, H2O was the most effective reforming agent for removing carbon followed by O2 and then CO2. H2O and CO2, however, left the anode only partially oxidized, while prolonged exposure to O2 completely oxidized Ni to nickel oxide. The spectroscopic and electrochemical data showed strong correlations that provide mechanistic insight into the consequences of adding secondary materials to SOFC anodes with the intent of reducing carbon accumulation.