A new family of electrochemical cells ((Electro-catalytic electrode) /Pt(Cathode) / YSZ / Pt(Anode)) for NO decomposition in the presence of excess oxygen have been designed and investigated. It was shown that by control of the composition of the (NiO)(x)-(YSZ)(1-x) electro-catalytic electrode, it was possible to minimize the values of the cell operating voltage. The electrochemical properties of an electrochemical cell for NO decomposition were investigated and correlated with the compositions of the (NiO)(x)-(YSZ)(1-x) electro-catalytic electrode using the effective medium percolation theory (EMPT). The optimum NiO addition (35% by volume) to the electro-catalytic electrode resulted in a decrease of the cell operating voltage and in a decrease in the electrical power required for NO decomposition. A mechanism of NO decomposition by this new type of the electrochemical cell with composite electro-catalytic electrode was proposed and investigated. (C) 2003 Elsevier Science B.V. All rights reserved.