The protonic ceramic electrochemical cell (PCEC) is an emerging and attractive technology that converts energy between power and hydrogen using solid oxide proton conductors at intermediate temperatures. To achieve efficient electrochemical hydrogen and power production with stable operation, highly robust and durable electrodes are urgently desired to facilitate water oxidation and oxygen reduction reactions, which are the critical steps for both electrolysis and fuel cell operation, especially at reduced temperatures. In this study, a triple conducting oxide of PrNi 0.5 Co 0.5 O 3-δ perovskite is developed as an oxygen electrode, presenting superior electrochemical performance at 400~600°C. More importantly, the selfsustainable and reversible operation is successfully demonstrated by converting the generated hydrogen in electrolysis mode to electricity without any hydrogen addition. The excellent electrocatalytic activity is attributed to the considerable proton conduction, as confirmed by hydrogen permeation experiment, remarkable hydration behavior and computations.

The oxidation of ferritic stainless steels has been studied under solid oxide fuel cell ͑SOFC͒ interconnect ''dual'' exposure conditions, i.e., simultaneous exposure to air on one side of the sample, and moist hydrogen as the fuel on the other side. The scales grown on the air side under these dual exposure SOFC conditions can be significantly different from scales grown on samples exposed to air on both sides. In contrast, no substantial difference was observed between scales grown on the fuel side of the dual atmosphere samples and scales grown on samples exposed to moist hydrogen on both sides. The anomalous oxidation of stainless steels at the air side depends on both alloy composition and thermal history. AISI430, with 17% Cr, suffered localized attack via formation of Fe 2 O 3 hematite-rich nodules on the air side of dual exposure samples, while the spinel top layer of the air side scale of Crofer22 APU ͑23% Cr͒ was enriched in iron. For E-brite, with the highest Cr content ͑27%͒, no unusual phases were found in the scale on the air side, but the air side scale was less dense and appeared to be more prone to defects than the scale grown in air only. Increasing temperature and thermal cycling both accelerated the anomalous oxidation, which appeared to be related to the transport of hydrogen through the steel and its subsequent presence in the air side scale.

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In its most common configuration, a solid oxide fuel cell (SOFC) uses an oxygen‐ion conducting ceramic electrolyte membrane, perovskite cathode, and nickel cermet anode electrode. Cells operate in the 600–1000°C temperature range and utilize metallic or ceramic current collectors for cell‐to‐cell interconnection. Recent developments in engineered electrode architectures, component materials chemistry, cell and stack designs, and fabrication processes have led to significant improvements in the electrical performance and performance stability as well as reduction in the operating temperature of such cells. Large kW‐size power‐generation systems have been designed and field demonstrated. This paper reviews the status of SOFC power‐generation systems with emphasis on cell and stack component materials, electrode reactions, materials reactions, and corrosion processes.