Selective decomposition of nitrogen monoxide to nitrogen in the presence of oxygen on RuO 2/Ag(cathode)/yttria-stabilized zirconia/Pd(anode)

Abstract

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 RuO 2≫Pt>Rh 2O 3>Ni>none>Ag>WO 3. The activity of the system modified by RuO 2 has been investigated as a function of the kind of electrode, the applied voltage, and the reaction temperature. The cell of RuO 2/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.