Ritzmann Andrew M, Dieterich Johannes M, Carter Emily A
Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA.
Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA.
Phys Chem Chem Phys. 2016 Apr 28;18(17):12260-9. doi: 10.1039/c6cp01720g.
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).
降低工作温度是使固体氧化物燃料电池（SOFC）技术可行的关键一步。实现这一目标的一个有前景的策略是采用混合离子电子传导（MIEC）阴极。La1-xSrxCo1-yFeyO3-δ（LSCF）是应用最广泛的MIEC阴极材料；然而，对LSCF组成进行合理优化需要深入了解其电子结构与缺陷化学之间的联系。为了提供必要的见解，采用密度泛函理论加U（DFT+U）计算来研究LSCF（xSr = 0.50，yCo = 0.25）的电子结构。DFT+U计算表明，由于添加了钴，LSCF的电子结构与La1-xSrxFeO3有显著不同，但La0.5Sr0.5Co0.25Fe0.75O3和La0.5Sr0.5Co0.5Fe0.5O3之间的电子结构差异最小。计算了La0.5Sr0.5Co0.25Fe0.75O3中不同局部环境下的氧空位形成能（ΔEf,vac）。这些结果表明，某些构型具有最高的ΔEf,vac，而某些构型具有最低的ΔEf,vac，并且可能作为某些物质的陷阱。我们得出结论，Fe含量高于Co的组成更受青睐，因为额外的位点将导致更高的整体ΔEf,vac（和更低的浓度），而这些位点的俘获强度相对较弱（约0.3 eV）。
