TY - JOUR
T1 - Density functional theory + U analysis of the electronic structure and defect chemistry of LSCF (La0.5Sr0.5Co0.25Fe0.75O3-:δ)
AU - Ritzmann, Andrew M.
AU - Dieterich, Johannes M.
AU - Carter, Emily A.
N1 - Funding Information:
The simulations presented in this article were performed on computational resources supported by the Princeton Institute for Computational Science and Engineering (PICSciE) and the Office of Information Technology's High Performance Computing Center at Princeton University. HeteroFoaM, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under award number DE-SC0001061, supported this work. We thank Professors Michele Pavone, Ana B.Mun?z-Garc?a, and John A. Keith for helpful discussions. We also thank Nari Baughman for her help revising this manuscript.
Publisher Copyright:
© 2016 the Owner Societies.
PY - 2016
Y1 - 2016
N2 - Reducing operating temperatures is a key step in making solid oxide fuel cell (SOFC) technology viable. A promising strategy for accomplishing this goal is employing mixed ion-electron conducting (MIEC) cathodes. La1-xSrxCo1-yFeyO3-δ (LSCF) is the most widely employed MIEC cathode material; however, rational optimization of the composition of LSCF requires fundamental insight linking its electronic structure to its defect chemistry. To provide the necessary insight, density functional theory plus U (DFT+U) calculations are used to investigate the electronic structure of LSCF (xSr = 0.50, yCo = 0.25). The DFT+U calculations show that LSCF has a significantly different electronic structure than La1-xSrxFeO3 because of the addition of cobalt, but that minimal electronic structure differences exist between La0.5Sr0.5Co0.25Fe0.75O3 and La0.5Sr0.5Co0.5Fe0.5O3. The oxygen vacancy formation energy (ΔEf,vac) is calculated for residing in different local environments within La0.5Sr0.5Co0.25Fe0.75O3. These results show that configurations have the highest ΔEf,vac, while have the lowest ΔEf,vac and may act as traps for. We conclude that compositions with more Fe than Co are preferred because the additional sites would lead to higher overall ΔEf,vac (and lower concentrations), while the trapping strength of the sites is relatively weak (∼0.3 eV).
AB - Reducing operating temperatures is a key step in making solid oxide fuel cell (SOFC) technology viable. A promising strategy for accomplishing this goal is employing mixed ion-electron conducting (MIEC) cathodes. La1-xSrxCo1-yFeyO3-δ (LSCF) is the most widely employed MIEC cathode material; however, rational optimization of the composition of LSCF requires fundamental insight linking its electronic structure to its defect chemistry. To provide the necessary insight, density functional theory plus U (DFT+U) calculations are used to investigate the electronic structure of LSCF (xSr = 0.50, yCo = 0.25). The DFT+U calculations show that LSCF has a significantly different electronic structure than La1-xSrxFeO3 because of the addition of cobalt, but that minimal electronic structure differences exist between La0.5Sr0.5Co0.25Fe0.75O3 and La0.5Sr0.5Co0.5Fe0.5O3. The oxygen vacancy formation energy (ΔEf,vac) is calculated for residing in different local environments within La0.5Sr0.5Co0.25Fe0.75O3. These results show that configurations have the highest ΔEf,vac, while have the lowest ΔEf,vac and may act as traps for. We conclude that compositions with more Fe than Co are preferred because the additional sites would lead to higher overall ΔEf,vac (and lower concentrations), while the trapping strength of the sites is relatively weak (∼0.3 eV).
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U2 - 10.1039/c6cp01720g
DO - 10.1039/c6cp01720g
M3 - Article
C2 - 27079696
AN - SCOPUS:84966365342
SN - 1463-9076
VL - 18
SP - 12260
EP - 12269
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 17
ER -