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ACS Appl Mater Interfaces. 2018 Nov 21;10(46):39785-39793. doi: 10.1021/acsami.8b14693. Epub 2018 Nov 12.

Improving the Electrocatalytic Activity and Durability of the La0.6Sr0.4Co0.2Fe0.8O3-δ Cathode by Surface Modification.

Author information

1
Guangzhou Key Laboratory for Surface Chemistry of Energy Materials, New Energy Institute, School of Environment and Energy , South China University of Technology , Guangzhou 510006 , China.
2
School of Advanced Materials , Shenzhen Graduate School, Peking University , Shenzhen 518055 , China.
3
Materials Science and Engineering , Georgia Institute of Technology , Atlanta , Georgia 30332-0245 , United States.
4
Institute of Nuclear and New Energy Technology (INET) , Tsinghua University , Beijing 100084 , China.
5
Institute of Nuclear Physics and Chemistry , China Academy of Engineering Physics , Mianyang 621000 , China.
6
Guangdong Engineering and Technology Research Center for Surface Chemistry of Energy Materials, School of Environment and Energy , South China University of Technology , Guangzhou 510006 , PR China.

Abstract

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 Pr xCe1- 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.

KEYWORDS:

electrodes; oxide heterostructures; oxygen defects; oxygen reduction reaction; surface engineering

PMID:
30372019
DOI:
10.1021/acsami.8b14693

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