In this study electrochemical impedance spectroscopy (EIS) was used for characterization of composite electrodes of La1-xSrxCo1-yFeyO3-delta (x = 0.25, 0.40 and y = 0.8, 1) and Ce0.9Gd0.1O1.95 (CGO10) or Ce0.8Pr0.2O2 (CPO20). Symmetrical cells were produced by screen printing the electrodes on CGO10 and subjected to EIS while varying the atmosphere between 1% NO in Ar, 1% NO2 in Ar, and air in the temperature range of 300-600 degrees C. The electrodes did not react directly with NO around open circuit voltage, but instead with an intermediate, likely NO2. Electrodes with 25% Sr had increased electrochemical activity in air compared to the ones with 40% Sr; the same was seen for electrodes in 1% NO in Ar if they contained 20% Co at the B-site. Substitution on the B-site with 20% Co increased the electrochemical activity of the electrodes, both in air and in 1% NO in Ar. Replacing CGO10 with CPO20 increased the cells electrochemical activity in 1% NO in Ar, and the apparent selectivity also increased. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3496042] All rights reserved.