Removal of Nitric Oxide (NO) by Perovskite‐Type Composite Catalytic Thick Film, La0.6Sr0.4Co0.2Fe0.8O3−δ and Gadolinia‐Doped Ceria Electrolyte, Gd0.2Ce0.8O2−δ

Abstract

Electrochemical cells consisting of a La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)–Gd0.2Ce0.8O2−δ (CGO) composite catalytic electrode and a CGO solid electrolyte were fabricated for direct nitric oxide (NO) decomposition, and the electrocatalytic properties and NO decomposition behaviors of the cells were investigated. The electrochemical cells were operated at 600°C in a reactant gas mixture containing 1000 ppm NO and 2% O2 in He, with a flow rate of 50 mL/min. LSCF sintered at temperatures <1000°C seemed to be a better electrode for oxygen reduction than LSCF sintered at 1100°C and platinum (Pt) (+CGO) sintered at 1000°C. An LSCF/CGO/LSCF electrochemical cell sintered at high temperature showed low ohmic resistance, because of good physical contact between the LSCF and the CGO, whereas grain growth and crystal‐structure change appeared to lead to high polarization resistance. Two electrochemical reactions, NO and O2 reductions, occurred at the cathode when the electric current was applied to the electrochemical cells. Of the two reactions, O2 reduction was the preferred reaction, and this tendency was predominant at the LSCF electrode, which had a high affinity for oxygen. Although the onset current for NO decomposition of the LSCF/CGO/LSCF electrochemical cell was slightly higher than that of the other electrochemical cells, excess oxygen could be effectively pumped at a relatively low voltage (<1.3 V at 600°C). As a result, the LSCF/CGO/LSCF electrochemical cell significantly decreased the electric power needed to decompose NO.