YSZ((X))- Pt(1-X) (YSZ, yttria-stabilized zirconia) ceramics have been studied as a cathode for electrochemical cells (electrocatalytic electrode)\(cathode)\YSZ\(anode) for selective NO decomposition. A YSZ-Pt cathode with high electronic conductivity along the cathode plane and with high oxygen ionic conductivity in the direction perpendicular to the electrocatalytic electrode through the cathode to the YSZ solid electrolyte was successfully designed. The conductivity of the YSZ-Pt cathode was investigated and correlated with the composition of the cathode using the two-dimensional percolation model. The optimum cathode composition (YSZ less than or equal to 50% by volume) resulted in a decrease of the cell operating voltage and a decrease in the electrical power required for NO decomposition. The electrochemical properties of a cell with a multilayer electrode for NO decomposition were investigated and correlated with the composition of the cathode. Structure evolution of the NiO-YSZ electrocatalytic electrode was studied by X-ray diffraction and correlated with the YSZ((X))- Pt(1-X) cathode composition. It was found that the highest rate of reduction of NiO into Ni in the NiO/YSZ interface regions occurred at the optimum cathode composition. (C) 2004 The Electrochemical Society.