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Dissolution of oxygen reduction electrocatalysts in an acidic environment: density functional theory study
The Journal of Physical Chemistry. A
|August 11, 2006
Summary
Density functional theory reveals iridium is the most stable pure metal against dissolution in acid medium oxygen reduction reaction catalysts. Alloying with platinum generally decreases platinum stability, except for nickel.
Area of Science:
- Computational chemistry
- Materials science
- Electrochemistry
Background:
- Investigating the stability of oxygen reduction reaction (ORR) catalysts is crucial for fuel cell technology.
- Dissolution of catalyst active sites, particularly platinum (Pt), leads to performance degradation.
- Understanding metal dissolution thermodynamics in acidic media is essential for designing durable catalysts.
Discussion:
- Density functional theory (DFT) calculations were used to model the thermodynamics of metal atom dissolution from ORR catalysts.
- Electrochemical dissolution pathways involving adsorbed oxygenated intermediates were identified as thermodynamically favorable.
- The relative stabilities of pure transition metals (Ir, Pd, Rh, Ni, Co) and their alloys with Pt were evaluated.
Key Insights:
- Iridium (Ir) exhibits superior stability against dissolution compared to pure platinum (Pt) and other transition metals studied.
- Alloying Pt with most transition metals (e.g., Ir, Pd, Rh, Co) decreases the stability of Pt against dissolution.
- Nickel (Ni) alloying with Pt does not significantly affect Pt stability, while Pt alloying with Ir enhances Ir stability.
Outlook:
- DFT provides a powerful tool for predicting catalyst stability under operating conditions.
- Further research into Pt-Ir and Pt-Co alloys may yield more durable ORR catalysts.
- Understanding dissolution mechanisms is key to developing strategies for enhanced catalyst longevity.
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