The role of ceria in LSM-GDC composite cathode for electrochemical reduction of nitric oxide

Abstract

Electrochemical reduction of nitric oxide (NO) in a solid state cell reactor (SSCR) is conducted at intermediate-temperature (500–550°C) using three (La0.85Sr0.15)0.9MnO3 (LSM)- Ce0.8Gd0.2O2 (GDC) composite cathodes (LSM:GDC=3:1, 2:2 and 1:3wt.%, denoted respectively as LSM-GDC31, LSM-GDC22, and LSM-GDC13). GDC-free LSM cathode is compared as blank sample. The NO conversion and current generation are evaluated. In the absence of oxygen, NO apparent conversion at the closed circuit state at 550°C is almost 60%, and the corresponding current density at 0.3V is 17mAcm−2 with LSM-GDC22. NO apparent conversion and current produced are greatly enhanced up to 80% and 66.7mAcm−2 in 2000ppm NO-10% O2 at 500°C due to the electrochemical promotion of catalysis (EPOC). The combined electrochemical impedance spectra, in-situ diffuse reflectance infrared fourier transform spectra, scanning electron microscope and Raman spectra are applied and prove that the oxygen-storage properties of ceria improves the selectivity towards NO electrochemical reduction in oxygen-rich atmosphere. In addition, the introduction of GDC enhances the electrode activities due to the increased three phase boundary (TPB) for oxygen reduction reaction.