Insight into Carbon Removal from Solid Oxide Fuel Cells via Operando Spectroscopy

Accumulated carbon (also termed coke) formed by hydrocarbon fuels on solid oxide fuel cell (SOFC) anodes blocks electrocatalytic sites at triple-phase boundaries, impedes transport through the porous electrode, and can react with nickel (Ni) to further degrade electrode performance. These effects are mitigated in the presence of oxygen-containing reformers such as H2O, CO2, and O2. However, the mechanism responsible for carbon abatement by reforming agents remains speculative, with many models proposed but little direct, experimental evidence to support them. In this work, we use operando near-infrared thermal imaging and Fourier transform infrared emission spectroscopy to expand on previous operando Raman spectroscopic studies that examined carbon gasification of a precoked Ni-YSZ membrane electrode assembly. The work presented in this article demonstrates significant differences in the gasification of carbon by H2O compared to similar concentrations of O2. These differences include spatially homogeneous cooling over the anode under humidified Ar corresponding to the endothermic gasification of carbon with H2O versus spatially heterogeneous heating over the anode under O2 that is localized near the gas entry port of the anode chamber. The anode surface temperature differences observed between H2O- and O2-driven gasification are discussed within the context of product evolution and the impact on the SOFC electrochemical performance.