Density Functional Theory Study of the Initial Stages of Cl-Induced Degradation of α-Cr2O3 Passive Film
Journal Article
·
· Journal of the Electrochemical Society
- Oregon State Univ., Corvallis, OR (United States)
- Univ. of Wisconsin, Madison, WI (United States); Idaho National Laboratory (INL), Idaho Falls, ID (United States)
The ion exchange and point defect models are two prominent models describing the role of anions, such as chlorides, in the degradation of passive oxide films. Here the thermodynamic feasibility of critical steps of Cl-induced degradation of a hydroxylated α-Cr2O3 (0001) surface, as proposed by these two models, are studied. Both models begin with Cl substitution of surface OH and H2O, which becomes less favorable with increasing Cl coverage. The initial stages of Cl-induced breakdown of the α-Cr2O3 depend on Cl coverage and the presence of O vacancy near the surface as follows: (1) neither Cl insertion (supporting the ion exchange model) nor Cr vacancy formation (supporting the point defect model) is feasible at low Cl coverages except in the presence of O vacancies near the surface, where Cl insertion is thermodynamically feasible even at low coverages, (2) in the absence of O vacancies, Cr vacancy formation becomes feasible from 10/12 ML onwards whereas Cl insertion by exchange with subsurface OH only becomes feasible at full coverage. This implies that at higher coverages Cl-induced degradation first initiates through a vacancy formation mechanism, but both insertion and vacancy formation would be feasible at full coverage.
- Research Organization:
- Idaho National Laboratory (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); USDOE Office of Nuclear Energy (NE), Nuclear Energy University Program (NEUP)
- Grant/Contract Number:
- AC07-05ID14517; NE0008668
- OSTI ID:
- 2371688
- Report Number(s):
- INL/JOU--20-57871-Rev000
- Journal Information:
- Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 12 Vol. 167; ISSN 0013-4651
- Publisher:
- IOP PublishingCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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