Stretching Epitaxial La0.6Sr0.4CoO3-δ for Fast Oxygen Reduction
arXiv:1712.05869 · doi:10.1021/acs.jpcc.7b06374
Abstract
The slow kinetics of the oxygen reduction reaction (ORR) is one of the key challenges in developing high performance energy devices, such as solid oxide fuel cells. Straining a film by growing on a lattice-mismatched substrate has been a conventional approach to enhance the ORR activity. However, due to the limited choice of electrolyte substrates to alter the degree of strain, a systematic study in various materials has been a challenge. Here, we explore the strain modulation of the ORR kinetics by growing epitaxial La0.6Sr0.4CoO3-δ (LSCO) films on yttria-stabilized zirconia substrates with the film thickness below and above the critical thickness for strain relaxation. Two orders of magnitude higher ORR kinetics is achieved in an ultra-thin film with ~0.8% tensile strain as compared to unstrained films. Time-of-flight secondary ion mass spectrometry depth profiling confirms that the Sr surface segregation is not responsible for the enhanced ORR in strained films. We attribute this enhancement of ORR kinetics to the increase in oxygen vacancy concentration in the tensile-strained LSCO film owing to the reduced activation barrier for oxygen surface exchange kinetics. Density functional theory calculations reveal an upshift of the oxygen 2p-band center relative to the Fermi level by tensile strain, indicating the origin of the enhanced ORR kinetics.
References in corpus (5)
- Strain controlled oxygen vacancy formation and ordering in CaMnO
- Enhancing Perovskite Electrocatalysis through Strain Tuning of the Oxygen Deficiency
- Strain Control of Oxygen Vacancies in Epitaxial Strontium Cobaltite Films
- Understanding and controlling the work function of perovskite oxides using Density Functional Theory
- Strain-Induced Spin States in Atomically Ordered Cobaltites