Effect of impregnation of La0.85Sr0.15MnO3/yttria stabilized zirconia solid oxide fuel cell cathodes with La0.85Sr0.15MnO3 or Al2O3 nano-particles

Abstract

Strontium substituted lanthanum manganite and yttria stabilized zirconia solid oxide fuel cell composite electrodes were impregnated with nano-particles of strontium substituted lanthanum manganite or alumina. A clear positive effect was observed on low performing electrodes and on good performing electrodes if the temperature was kept low after the impregnation with strontium substituted lanthanum manganite. On good performing electrodes the effect disappeared on heating.Alumina nano-particles had a detrimental effect on the activity of the strontium substituted lanthanum manganite based electrodes.

An Investigation of Oxygen Reduction Kinetics in LSF Electrodes

“…This observation is consistent with the results shown in Figure 2 (open symbol), where an increase in free oxygen vacancy sites was observed after heating the LSF coated with 50 cycles of Al 2 O 3 to 1073 K. These results provide strong evidence that the deactivation associated with the addition of Al 2 O 3 at lower temperatures is due to physical blocking of the surface, since one might expect electrode deactivation to be more pronounced after heating if deactivation were due to a chemical process, such as reaction between Al 2 O 3 and LSF. 24 Assuming that deactivation is due to physical blocking of the surface by Al 2 O 3 , the performance recovery at 1073 K likely results from the Al 2 O 3 film breaking up due to thermally induced mechanical stresses. In Figures 8 and 9, it is also important to notice the characteristic frequencies shift to lower values in the electrodes deactivated by Al 2 O 3 .…”

“…Al 2 O 3 was chosen because it is expected to act primarily as a physical blocker of electrochemical reactions on the surface of the perovskite, and not form a chemical compound with the LSF or act as a catalyst for O 2 adsorption. 24 As an added benefit, the deposition of Al 2 O 3 using trimethyl aluminum (TMA) and water as precursors is one of the most thoroughly characterized ALD systems. 36,39 The reaction between TMA and the substrate is rapid and has been shown to work well on a large number of different substrates.…”

“…4 Additional evidence that a surface process limits cathode performance comes from the strong dependence of cell impedance on the surface area of the perovskite phase of the composite cathode 4 and by the fact that cathode performance can be enhanced by the addition of various promoters onto the surface of the electrodes. 7,9,[16][17][18][19][20][21][22][23][24] Finally, a number of mathematical models have stressed the importance of maximizing the electrode active area 7,8,25,26 and point to the adsorption of molecular oxygen on a perovskite vacancy site as the most probable rate-limiting step. 7,8,10 Despite a large amount of work aimed at characterizing the oxygenreduction reaction on various materials, there is still much that is not known about the reaction or how to promote it.…”

Modifications of interface chemistry of LSM–YSZ composite by ceria nanoparticles

“…Examples for the impregnation of LSM-YSZ electrodes with various different materials and the effect of the nanoparticles and nanostructures on electrochemical performance were discussed in literature [5][6][7][8][9][10][11][12][13][14]. For example, it was shown that the presence of SDC (samarium substituted ceria) nanoparticles significantly improved the electrochemical performance of LSM-YSZ cathode materials [13,14].…”

Performance Improvement of an Inhomogeneous Cathode by Infiltration

“…This includes fabrication an electrode backbone, then infiltrating an aqueous salt precursor solution into the porous structure followed by calcination at temperatures typically only slightly higher than operating temperature. This technique helps bypass the high temperature methods by depositing catalytic nanoparticles inside the active porous electrode , . The nano particles may form continuous layers or discrete particles on the inner electrode surface.…”