NO Decomposition Property of Lanthanum Manganite Porous Electrodes
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NO Decomposition Property of Lanthanum Manganite Porous Electrodes Kazuyuki Matsuda, Takao Kanai, Masanobu Awano1 and Kunihiro Maeda Synergy Ceramics Laboratory, Fine Ceramics Research Association, Nagoya, 463-8687, JAPAN 1 National Industrial Research Institute of Nagoya, Nagoya, 463-8687, JAPAN ABSTRACT The NOx decomposition activity of electrochemical cells composed of YSZ solid electrolyte and La1-xCaxMnO3 porous electrodes was examined. La1-xCaxMnO3 powders were prepared by solid-state reaction using corresponding metal oxides and carbonates. The powders were dispersed in polyethylene glycol and screen-printed on both sides of the electrolyte pellet. The electrochemical decomposition of NO was carried out in the temperature range from 973 to 1173 K by passing a mixed gas of 1000 ppm NO and 2% O2 in He through the cell. When the DC voltage was applied to the cell, NO was directly decomposed to N2 and O2 in the oxidizing atmosphere. The cells composed of the La0.8Ca0.2MnO3 electrodes showed a higher NO decomposition ratio and current efficiency than that of other La1-xCaxMnO3 electrodes.
INTRODUCTION The exhaust gases from lean-burn and diesel engines contain NOx and O2. The emission of NOx causes serious environmental damage. Unfortunately, three-way catalysts cannot reduce NO to N2 under oxidizing atmospheres. The selective decomposition of NOx from exhaust gases containing O2 is an important subject. Recently, the electrochemical decomposition of NO using an electrochemical cell composed of a solid electrolyte and metal electrodes has been proposed [1,2]. In these cases, high current density is required to attain substantial NO decomposition. The manganite-based perovskite oxides are catalysts for NO decomposition [3], and these oxides have been widely used as the cathode for solid oxide fuel cells (SOFC) due to their high electrical conductivity, stability at high temperature and thermal expansion compatibility with YSZ. The purpose of this study is to evaluate the NO decomposition activity of electrochemical cells composed of 8mol% Y2O3 stabilized ZrO2 (YSZ) solid electrolyte and La1-xCaxMnO3 (x = 0.1-0.7) electrodes.
EXPERIMENTAL DETAILS Calcium substituted lanthanum manganite powders were prepared by solid-state reaction. La2O3 was fired at 1173 K for 3 hours before use, to remove adsorbed water. CaCO3, La2O3 and Mn3O4 were mixed in a desired ratio and calcined at 1673 K for 5 hours. The products were ground in a ball mill for 24 hours. La1-xCaxMnO3 pastes were prepared by mixing the La1xCaxMnO3 powders and polyethylene glycol. Electrochemical cells were constructed by screenprinting the pastes on both sides of the YSZ pellets (1 mm thick and 20 mm in diameter). The cells were sintered at 1373 K for 1 hour. The electrode surface area was 1.1cm2. Platinum mesh GG9.36.1
NO/He
Mass flow controller
O2
Mass flow controller
He
Mass flow controller
Potentiostat
Cell
Impedance Analyzer
Gas Chromatograph
Vent
NOx Analyzer
Figure 1. Schematic arrangement of the experimental apparatus. and wire was
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