Selective decomposition of nitrogen monoxide to nitrogen in the presence of oxygen on RuO2 Ag(cathode) yttria-stabilized zirconia Pd(anode)

Selective decomposition of nitrogen monoxide (NO) in the presence of oxygen was studied on electrochemical cells composed of yttria-stabilized zirconia (YSZ), electrodes, and surface oxide layers added. Decomposition activity was first measured on metal oxide/Pd(cathode)/YSZ/Pd(anode) at 773-973 K and 3.0 V of applied voltage in a flow of 50 ml/min containing 1000 ppm of NO and 6% of O-2 in helium. Coating of various metal oxides onto the cathode electrode greatly changed the decomposition activity; the order was RuO2>>Pt>Rh2O3>Ni>none>Ag>WO3. The activity of the system modified by RuO2 has been investigated as a function of the kind of electrode, the applied voltage, and the reaction temperature. The cell of RuO2/Ag(cathode)/YSZ/Pd(anode) was found to show the most excellent activity among the cells examined. The conversion of NO and the current efficiency for NO decomposition reached 31.8% and 11.8%, respectively, at 7 mA/cm(2) of current density induced by 2.2 V and 773 K, and the NO decomposition proceeded selectively about 13 times than the O-2 decomposition under the reaction condition. (C) 1998 Elsevier Science B.V. All rights reserved.