NO x conversion on porous LSF15–CGO10 cell stacks with KNO3 or K2O impregnation

Abstract

In the present work it was investigated how addition of KNO 3 or K 2 O affected the NO x conversion on LSF15-CGO10 (La 0.85 Sr 15 FeO 3 -Ce 0.9 Gd 0.1 O 1.95 ) composite electrodes during polarisation. The LSF15-CGO10 electrodes were part of a porous 11-layer cell stack with alternating layers of LSF15-CGO10 electrodes and CGO10 electrolyte. The KNO 3 was added to the electrodes by impregnation, and kept either as KNO 3 in the electrode or thermally decomposed into K 2 O before testing. The cell stacks were tested in the temperature range 300-500 °C in 1000 ppm NO, 10% O 2 and 1000 ppm NO + 10% O 2 . During testing the cells were characterized by electrochemical impedance spectroscopy (EIS) and the NO conversion was measured during polarization at -3 V for 2 h. The concentration of NO and NO 2 was monitored by a chemiluminiscence detector, while the concentration of O 2 , N 2 and N 2 O was detected on a mass spectrometer. A significant effect of impregnation with KNO 3 or K 2 O on the NO x conversion was observed. In 1000 ppm NO both impregnations caused an increased conversion of NO into N 2 in the temperature range 300-400 °C with a current efficiency up to 73%. In 1000 ppm NO + 10% O 2 no formation of N 2 was observed during polarisation, but the impregnations altered the conversion between NO and NO 2 on the electrodes. Both impregnations caused increased degradation of the cell stack, but the exact cause of the degradation has not been identified yet.

NOx conversion on LSM15-CGO10 cell stacks with BaO impregnation

“…The presence of such a process on perovskite/CGO10 electrodes is in good agreement with previous findings in our group. 28,30 Processes on impregnated electrodes…”

Effects of the Ba Impregnation on Pt Electrode on NO Electrochemical Reduction Mechanism

“…Both the impregnation of KNO 3 and MnOx can cause the decrease of the polarization resistance related to the formation of NO 2 from NO oxidation. They [26][27] (LSM-GDC) composite electrodes respectively based on the GDC electrolyte cell stacks. Results showed that high NOx conversion can be obtained with the NOx adsorption layer between 300°C and 500°C.…”

Diffuse Reflectance Infrared Fourier Transform Study of NOx Adsorption on CGO10 Impregnated with K2O or BaO

“…13−15 Frequently, a composite electrode is applied, i.e., an electrode with both an electron conducting phase (for instance, a perovskite) and an O 2− conducting phase (for instance, yttria stabilized zirconia (YSZ) or CGO). 13,15,16 An obstacle in the investigation and understanding of electrochemical deNO x is a limited knowledge of the adsorption of NO x on the electrode materials, and how this adsorption changes in the temperature ranges investigated for electrochemical deNO x (usually 300− 600 °C) and depending on the presence of NO or NO 2 . The aim in this work is to apply DRIFT (diffuse reflectance infrared Fourier transform) spectroscopy to study the NO x adsorption at conditions relevant for electrochemical deNO x .…”

“…In the investigation of suitable electrode materials for electrochemical deNO x a major challenge is to find electrode materials that have a sufficiently high activity and selectivity, i.e., which are capable of reducing NO x but not O 2 , as reduction of O 2 is a competing reaction on the cathode . Several electrode materials have been investigated for electrochemical deNO x , for example, noble metals, − spinels, and perovskites. − Frequently, a composite electrode is applied, i.e., an electrode with both an electron conducting phase (for instance, a perovskite) and an O 2– conducting phase (for instance, yttria stabilized zirconia (YSZ) or CGO). ,, An obstacle in the investigation and understanding of electrochemical deNO x is a limited knowledge of the adsorption of NO x on the electrode materials, and how this adsorption changes in the temperature ranges investigated for electrochemical deNO x (usually 300–600 °C) and depending on the presence of NO or NO 2 . The aim in this work is to apply DRIFT (diffuse reflectance infrared Fourier transform) spectroscopy to study the NO x adsorption at conditions relevant for electrochemical deNO x .…”

“…One of the intentions in this work is to relate the adsorption studies on CGO to findings on electrochemical removal of NO x . Three of the main findings from the conversion studies on electrochemical cells are as follows: 15,16,18,52 (1) The highest NO x conversion is found in NO atmospheres without presence of O 2 on both nonimpregnated and impregnated electrodes. (2) On nonimpregnated electrodes the conversion increases with temperature, but the selectivity/current efficiency decreases.…”