Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 10, Issue 46, Pages 39785-39793Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.8b14693
Keywords
surface engineering; oxygen reduction reaction; oxygen defects; electrodes; oxide heterostructures
Funding
- Guangzhou Science and Technology Program General Projects [201707010146]
- Fundamental Research Funds for the Central Universities [2018MS40]
- Guangdong Innovative and Entrepreneurial Research Team Program [2014ZT05N200]
- National Natural Science Foundation of China [11605063, 91745203]
- Science and Technology Planning Project of Guangdong Province, China [2017B090916002]
- Recruitment Program of Global Youth Experts of China
- Office of Science of the U.S. Department of Energy [DE-AC02-05CH11231]
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Electrode materials with high activity and good stability are essential for commercialization of energy conversion systems such as solid oxide fuel cells or electrolysis cells at the intermediate temperature. Modifying the existing perovskite-based electrode surface to form a heterostructure has been widely applied for the rational design of novel electrodes with high performance. Despite many successful developments in enhancing electrode performance by surface modification, some controversial results are also reported in the literature and the mechanisms are still not well understood. In this work, the mechanism of how surface modification impacts the oxygen reduction reaction (ORR) activity and stability of perovskite-based oxides was investigated. We took La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) as the thin-film model system and modified its surface with additive PrxCe1-xO2 layers of different thicknesses. We found a strong correlation between surface oxygen defects and the ORR activity of the heterostructure. By inducing higher oxygen vacancy concentration compared to bare LSCF, PrO2 coating is proved to greatly facilitate the rate of oxygen dissociation, thus significantly enhancing the ORR activity. Because of low oxygen vacancy density introduced by Pr0.2Ce0.8O2 and CeO2 coating, on the one hand, it does not boost the rate of ORR but successfully suppresses surface Sr segregation, leading to an enhanced durability. Our findings demonstrate the vital role of surface oxygen defects and provide important insights for the rational design of high-performance electrode materials through surface defect engineering.
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