期刊
ACS APPLIED MATERIALS & INTERFACES
卷 -, 期 -, 页码 -出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.2c10700
关键词
Mixed conductor; surface exchange reaction; ligand hole; X-ray photoelectron spectroscopy; (La; Ca)FeO3-?
资金
- JSPS KAKENHI
- [17H03391]
This study investigated the surface reaction mechanism of mixed conductive materials using operando X-ray photoelectron spectroscopy. The results showed that applying current from negative to positive can increase the number of active reaction sites, thereby improving oxygen evolution performance.
High oxygen permeability of mixed conductive La0.65Ca0.35FeO3-delta (LCF) is applicable to pure oxygen gas generators and cathodes for solid oxide fuel cells, etc.; however, lower surface exchange reactions at temperatures below 800 degrees C reduce permeability. To understand the microscopic surface reaction mechanism, operando soft X-ray photoelectron spectroscopy of an LCF film surface was conducted during the evolution and incorporation of oxygen. LCF film was prepared on yttria-stabilized zirconia and a current was applied throughout the film at similar to 600 degrees C. From operando X-ray photoelectron spectra, surface oxide species involved in the surface exchange reaction obviously appeared on the film during the evolution of oxygen from the surface. The number of surface oxide species abruptly decreased during incorporation of oxygen. By applying the current from a negative to positive value, the numbers of surface oxide species and ligand holes near Fe3+ ions on the surface both significantly increased. The results infer that ligand holes in the Fe 3d-O 2p hybrid orbitals correspond to active reaction sites at which surface oxide species change to oxygen molecules. Increasing the number of active reaction sites is key to improving oxygen evolution of mixed conductive oxides.
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