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Synthesis of Bimetallic Pt/Sn-based Nanoparticles in Ionic Liquids
Published on: August 23, 2018
Long-range segregation phenomena in shape-selected bimetallic nanoparticles: chemical state effects
Mahdi Ahmadi1, Farzad Behafarid, Chunhua Cui
1Department of Physics, University of Central Florida , Orlando, Florida 32816, United States.
ACS Nano
|September 11, 2013
Summary
Nickel segregation on platinum-nickel nanoparticles is influenced by their chemical state and environment. Surface composition changes affect electrocatalytic CO oxidation activity, revealing alloy formation dynamics.
Area of Science:
- Materials Science
- Nanotechnology
- Surface Chemistry
Background:
- Shape-selected octahedral platinum-nickel (Pt0.5Ni0.5) nanoparticles (NPs) are crucial for catalysis.
- Understanding their morphological and chemical stability is key to optimizing performance.
- Support interactions, such as on highly oriented pyrolytic graphite (HOPG), influence NP behavior.
Purpose of the Study:
- To investigate the morphological and chemical stability of Pt0.5Ni0.5 NPs on HOPG.
- To monitor NP mobility and study atomic segregation and alloy formation under various conditions.
- To correlate NP surface composition with electrocatalytic CO oxidation activity.
Main Methods:
- Ex situ atomic force microscopy (AFM) for morphological analysis.
- In situ X-ray photoelectron spectroscopy (XPS) for chemical state and surface composition analysis.
- Controlled environments including vacuum, H2, and O2 with varying thermal treatments.
Main Results:
- Nickel (Ni) segregation to the NP surface was observed in all environments when platinum oxide (PtOx) species were present.
- Enhanced Ni surface segregation occurred in the presence of oxygen at all temperatures.
- In H2 and vacuum, Ni segregation was limited to lower temperatures (<200-270 °C) while PtOx persisted; higher temperatures led to Pt diffusion and Ni-Pt alloy formation.
Conclusions:
- The chemical state of Pt0.5Ni0.5 NPs significantly dictates their surface composition and stability.
- Environmental conditions (vacuum, H2, O2) and temperature control atomic segregation and alloy formation.
- A direct correlation exists between NP surface composition and electrocatalytic CO oxidation activity, highlighting the importance of surface engineering.
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