Electrical performance degradation relating to materials interactions at elevated temperatures is one of the primary technical limitations to the near term successful commercialization of solid oxide electrolysis cells (SOECs). Electrochemical performance and structural degradation of nickel-YSZ fuel electrodes (SOEC cathodes) were studied as functions of materials, preparation techniques, and operating conditions. Significant electrochemical degradation was observed in cells operated at 840 degrees C with and without voltage bias. Carbon deposition, Ni evaporation, and impurity poisoning were not observed to negatively affect performance. However, the high Ni content and large initial Ni particle size caused rapid Ni migration and agglomeration. The agglomeration reduced Ni electrical interconnectivity as well as contact area with the current collector. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.