The electrochemical properties of the interface between Ni and yttria-stabilized zirconia (YSZ) in the H-2-H2O-Ni-YSZ electrode have been investigated in order to obtain knowledge on the effect of segregation of impurities to the electrode-electrolyte interface on performance. Even for a relatively pure nickel electrode, a film of impurities was found at the contact between Ni and YSZ and on the surface of YSZ. Impurity ridges were also found at the three-phase boundary. Impurities in these locations all have the potential of impeding processes and reactions at the electrode-electrolyte interface. The pure electrodes showed a lower resistance compared to most electrodes discussed in the literature. (C) 2004 The Electrochemical Society.