Oxygen Sorption and Desorption Properties of Selected Lanthanum Manganites and Lanthanum Ferrite Manganites

Jimmi Nielsen, Eivind M. Skou, Torben Jacobsen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Temperature‐programmed desorption (TPD) with a carrier gas was used to study the oxygen sorption and desorption properties of oxidation catalysts and solid‐oxide fuel cell (SOFC) cathode materials (La0.85Sr0.15)0.95MnO3+δ (LSM) and La0.60Sr0.40Fe0.80Mn0.20O3‐δ (LSFM). The powders were characterized by X‐ray diffractometry, atomic force microscopy (AFM), and BET surface adsorption. Sorbed oxygen could be distinguished from oxygen originating from stoichiometry changes. The results indicated that there is one main site for oxygen sorption/desorption. The amount of sorbed oxygen was monitored over time at different temperatures. Furthermore, through data analysis it was shown that the desorption peak associated with oxygen sorption is described well by second‐order desorption kinetics. This indicates that oxygen molecules dissociate upon adsorption and that the rate‐determining step for the desorption reaction is a recombination of monatomic oxygen. Typical problems with re‐adsorption in this kind of TPD setup were revealed to be insignificant by using simulations. Finally, different key parameters of sorption and desorption were determined, such as desorption activation energies, density of sorption sites, and adsorption and desorption reaction order.
Original languageEnglish
JournalChemPhysChem
Volume16
Issue number8
Pages (from-to)1635-1645
Number of pages11
ISSN1439-4235
DOIs
Publication statusPublished - 2015

Keywords

  • Chemisorption
  • Fuel cells
  • Perovskites
  • Strontium‐doped lanthanum manganite
  • Temperature‐programmed desorption

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