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.