Metastable morphological states of catalytic nanoparticles
Pin Ann Lin1, Bharath Natarajan, Michael Zwolak
1Center of Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland, USA. michael.zwolak@nist.gov renu.sharma@nist.gov.
Nanoscale
|February 21, 2018
Summary
Catalytic nanoparticles form metastable states during carbon nanostructure synthesis. These nanoparticles elongate and retract in a cycle influenced by structure tapering, impacting catalyst lifetime and product formation.
Area of Science:
- Materials Science
- Nanotechnology
- Chemical Engineering
Background:
- Catalytic synthesis of nanostructures involves complex phenomena like phase separation and precipitation.
- Understanding nanoparticle behavior is crucial for controlling nanostructure growth.
Purpose of the Study:
- To investigate the functional, metastable states of catalytic nanoparticles during carbon nanostructure synthesis.
- To elucidate the thermodynamic cycle governing nanoparticle behavior and its influence on product formation.
Main Methods:
- In situ, real-time transmission electron microscopy (TEM) imaging.
- Thermodynamic modeling of nanoparticle-nanostructure interactions.
- Analysis of energy landscapes and phase transitions.
Main Results:
- Catalytic nanoparticles exhibit metastable states, elongating due to metal-carbon interactions overriding surface energy.
- Nanoparticle retraction is driven by free energy changes, allowing continued catalysis within nested structures.
- Structure tapering universally influences the elongation-retraction cycle, determining catalyst lifetime and final product.
Conclusions:
- A unifying nonequilibrium thermodynamic framework explains nanoparticle behavior in catalytic nanostructure synthesis.
- Findings offer insights into CO oxidation and boron nitride nanotube growth.
- Provides routes for optimizing catalytic processes and catalyst longevity.
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