Kinetics of oxidation of fuel cell cathode materials lanthanum strontium manganates (III)(IV) at actual working conditions: In situ powder diffraction studies
- Odense Univ. (Denmark). Dept. of Chemistry
- Brookhaven National Lab., Upton, NY (United States). Chemistry Dept.
Strontium substituted lanthanum manganates(III)(IV), La{sub 1{minus}x}Sr{sub x}MnO{sub 3+{delta}} (LSM) are cathode materials for high temperature solid oxide fuel cells/SOFC. Time resolved synchrotron X-ray powder diffraction methods have been used to study the kinetics of oxidation of lanthanum strontium manganates(III, IV) in a flow of oxygen. The process studied is La{sub 1{minus}x}Sr{sub x}MnO{sub 3.00} + {delta}/2O{sub 2}{leftrightarrow}La{sub 1{minus}x}Sr{sub x}MnO{sub 3.00+{delta}} (for x = 0.00, 0.10, 0.15). A contraction of the unit cell is observed on oxidation of the materials. The unit cell volume changes linearly with the mean oxidation state of the manganese. Rate constants for the process can consequently be determined from time resolved X-ray diffractograms. The reactions follow first-order kinetics. Arrhenius plots based on rate constants determined at 4 temperatures in the range 700--900 C are linear as an indication that only one rate determining step is involved. The activation energy for oxidation is 136 kJmol{sup {minus}1} for LaMnO{sub 3.00}, 179 kJmol{sup {minus}1} for La{sub 0.90}Sr{sub 0.10}Mn{sub 1.01}O{sub 3.01}, and 160 kJmol{sup {minus}1} for La{sub 0.84}Sr{sub 0.15}Mn{sub 1.01}O{sub 3.00}.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- Statens Naturvidenskabelige Forskningsraad, Copenhagen (Denmark); USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 329121
- Journal Information:
- Journal of Solid State Chemistry, Vol. 141, Issue 1; Other Information: PBD: 15 Nov 1998
- Country of Publication:
- United States
- Language:
- English
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