Solid oxide fuel cells (SOFCs) are a rapidly emerging energy technology for a low carbon world, providing high efficiency, potential to use carbonaceous fuels, and compatibility with carbon capture and storage. However, current state-of-the-art materials have low tolerance to sulfur, a common contaminant of many fuels, and are vulnerable to deactivation due to carbon deposition when using carbon-containing compounds. In this review, we first study the theoretical basis behind carbon and sulfur poisoning, before examining the strategies toward carbon and sulfur tolerance used so far in the SOFC literature. We then study the more extensive relevant heterogeneous catalysis literature for strategies and materials which could be incorporated into carbon and sulfur tolerant fuel cells.

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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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Energy storage is a critical component to supply local energy generation for both grid and off‐grid connected facilities and communities, enabling localized grid independent energy secure power in cases of emergencies or unreliable traditional grid use. The high cost and energy security of importing fuel to islanded grids has led to a growing need to generate power onsite with alternative and renewable energy technologies while reducing facility costs of importing electrical power. However, utility grid operators are being faced with the challenges of intermittent and variability in energy production from renewables. Therefore, energy storage is crucial to balance micro and utility grids, improve efficiency, reduce fuel consumption, and provide critical power in the event of power outages. There has been particular interest in reversible solid oxide fuel cells (RSOFCs) in the energy sector for electricity, energy storage, grid stabilization and improvement to power plant system efficiency due to favorable thermodynamic efficiencies of high temperature steam electrolysis. Boeing has been active in the development of a fully integrated, grid tied RSOFC system for micro grid and commercial utility energy storage using Sunfire fuel cell technology. In this system, excess grid energy or curtailed power generated by renewables is sent to the system operating in electrolysis mode to produce H2. The H2 is stored and then used in the system's fuel cell mode to provide supplemental power to the grid during peak hours or as needed. As part of this program, Boeing has developed a H2 storage and compression system, power distribution system, and master controller to interface with RSOFC subsystems. Sunfire developed a reversible solid oxide cell module with a power output of 50 kW in SOFC mode and 120 kW input in electrolysis mode producing 3.5 kg H2 hr−1. The system was demonstrated while connected to the local utility grid and operated in a microgrid test environment. This paper will discuss the development, integration, and demonstration of the RSOFC system.