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Fuel cells are likely to play a key role in any low-carbon economy. Solid oxide fuel cells (SOFCs) are currently capable of sustained and continuous operation on high-purity fuels, but they must demonstrate that they can overcome a number of challenges before they are commercially viable on a large scale. Fuels such as natural gas, and those derived from renewable sources such as gasified biomass, contain many contaminants, typically sulfur-and carbon-containing compounds. To address this it will be necessary to improve our understanding of failure modes in operating SOFCs, and act on this to reduce degradation rates. A combination of techniques will be needed to develop a rigorous approach to understanding and mitigating degradation. The intent of this article is to present a synopsis of the current state of the art in our understanding of the effect of carbon and sulfur on SOFC anodes. Emphasis is placed on the comparison between thermodynamic and kinetic models, and experimental validation of these. In particular the applicability of thermodynamic models to the study of such contaminants is questioned. Additionally the uses of multiscale kinetic models capable of predicting transient conditions are reviewed alongside recent analytical techniques necessary for their validation.

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Degradation of a polymer electrolyte membrane fuel cell (PEMFC) with electrosprayed cathode catalyst layers is investigated during cyclic start-up and shut-down events. The study is carried out within a single cell incorporating an array of reference electrodes that enables measurement of cell current as a function of local cathode potential (localized polarization curves). Accelerated degradation of the cell by start-up/shut-down cycling gives rise to inhomogeneous performance loss, which is more severe close to the gas outlet and occurs predominantly during start-up. The degradation consists primarily of loss of cathode catalyst activity and increase in cell internal resistance, which is attributed to carbon corrosion and Pt aggregation in both anode and cathode. Cells with an electrosprayed cathode catalyst layer show lower degradation rates during the first 100 cycles, compared with those of a conventional gas diffusion electrode. This difference in behavior is attributed to the high hydrophobicity of the electrosprayed catalyst layer microstructure, which retards the kinetics of corrosion of the carbon support. In the long term, however, the degradation rate is dominated by the Pt/C ratio in the cathode catalyst layer.

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