期刊
JOURNAL OF PHYSICS-ENERGY
卷 4, 期 4, 页码 -出版社
IOP Publishing Ltd
DOI: 10.1088/2515-7655/ac8a76
关键词
Ce0.75Zr0.25O2; ceria-zirconia solid solution; phase stability; complete dissociation; enhanced cation diffusion
资金
- Energy Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) - Ministry of Trade, Industry and Energy, Republic of Korea [20193010032460]
- KIST
- Education and Research Promotion Program of KOREATECH in 2022
- Korea Institute of Energy Technology Evaluation & Planning (KETEP) [20193010032460] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
Solid solution CeO2-ZrO2 has been widely used in three-way catalysts due to its high oxygen storage capacity. However, the stability of CeO2-ZrO2 has been a controversial issue. This study demonstrates theoretically and experimentally that a Ce0.75Zr0.25O2 solid solution will completely separate into CeO2 and ZrO2 phases due to its inherent thermodynamic instability. The enhanced cation diffusion in a reducing atmosphere is responsible for the inherent stability problem and increased phase separation kinetics of CZO materials.
Solid solution CeO2-ZrO2 has long been used as a non-noble metal oxide promoter for three-way catalysts owing to its high oxygen storage capacity. However, the stability issue of the CeO2-ZrO2 has been controversial for a long time. In particular, the phenomena observed by phase instability are so diverse and inconsistent that the related causal analysis is still a matter of debate. In this study, for the first time, it was demonstrated theoretically and experimentally that a Ce0.75Zr0.25O2 (CZO) solid solution must be completely separated into CeO2 and ZrO2 phases owing to its inherent thermodynamic instability. According to an extensive evaluation via defect chemical calculations and well-controlled model experiments with grain-boundary-free epitaxial thin film samples, CZO materials undergo phase separation until they are completely separated, and the separation rate is particularly high in a reducing atmosphere. The underlying inherent stability problem and enhanced phase separation kinetics of the CZO material are attributed to the enhanced cation diffusion in a reducing atmosphere, where more mobile cationic defects (interstitial cations) are generated and an easier pathway with a lower migration energy is available.
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