Abstract
The bulk-to-surface Sr segregation can seriously compromise the stability of oxygen electrocatalysis in La1-xSrxCoO3-δ and limit its practical applications such as in solid oxide fuel cells. Here we show via in situ ambient pressure X-ray photoelectron spectroscopy (APXPS) that the surface Sr-segregation is a kinetically fast process and the equilibrium surface Sr-concentration follows Arrhenius law from 250 to 520 °C at a fixed pO2 = 1 × 10-3 atm. We also show that application of a nanoscaled, atomic layer deposition (ALD) derived ZrO2 overcoat can effectively suppress the Sr-segregation by reducing the surface concentration of oxygen vacancies. Electrochemical impedance spectroscopy (EIS) study further confirms that the ALD-ZrO2-coated LSCo epitaxial film exhibits a much lower and more stable polarization resistance than the uncoated one at 550 °C for >300 hours, suggesting that Sr-segregation is the source of the higher resistance.
| Original language | English |
|---|---|
| Pages (from-to) | 24378-24388 |
| Number of pages | 11 |
| Journal | Journal of Materials Chemistry A |
| Volume | 6 |
| Issue number | 47 |
| DOIs | |
| State | Published - 2018 |
Funding
This work is supported by National Science Foundation (NSF) under award NSF-DMR-1464112. We would like to thank Dr Yi Yu and Jun Cai in Lawrence Berkeley National Laboratory for the assistance with APXPS, and Kang-Deuk Choi in Park Systems for the assistance with AFM. This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. This research also used resources of PLD thin lm deposition at Oak Ridge National Laboratory supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Science and Engineering Division.
