Related Experiment Video
Updated: May 10, 2026
08:55
Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Strained lattice with persistent atomic order in Pt3Fe2 intermetallic core-shell nanocatalysts.
Sagar Prabhudev1, Matthieu Bugnet, Christina Bock
1Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada L8S 4L8.
ACS Nano
|June 19, 2013
Summary
Ordered platinum-iron (Pt3Fe2) core-shell nanocatalysts show remarkable stability and activity for proton exchange membrane fuel cells. Their unique structure maintains performance over 10,000 cycles, crucial for commercialization.
Area of Science:
- Materials Science
- Electrochemistry
- Nanotechnology
Background:
- Proton exchange membrane fuel cells (PEMFCs) require highly active and durable nanocatalysts for commercial viability.
- Platinum-based nanocatalysts are essential for the oxygen reduction reaction (ORR) in PEMFCs, but their activity and durability need enhancement.
Purpose of the Study:
- To quantify the structural ordering and time evolution of ordered Pt3Fe2 intermetallic core-shell nanocatalysts.
- To investigate the relationship between structural changes, catalytic activity, and durability during the oxygen reduction reaction.
Main Methods:
- Aberration-corrected scanning transmission electron microscopy (STEM) for atomic-scale imaging.
- X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) for structural and compositional analysis.
- 2-D surface relaxation and lattice strain mapping.
Main Results:
- Ordered Pt3Fe2 core-shell nanocatalysts exhibited a 228% increase in mass activity and 155% enhanced catalytic activity compared to Pt/C.
- A static core-dynamic shell regime was observed, with negligible activity decrease (9%) after 10,000 cycles.
- The ordered Pt3Fe2 core remained intact, while the Pt shell showed continuous enrichment; enhanced surface relaxation and -3% lattice strain were noted.
Conclusions:
- The enhanced activity is attributed to the strained lattice structure of the nanocatalysts.
- The sustained atomic order of the core is responsible for the extended catalytic durability.
- These findings are critical for designing next-generation, high-performance nanocatalysts for fuel cell applications.
Related Concept Videos
02:37Metallic Solids
Metallic solids such as crystals of copper, aluminum, and iron are formed by metal atoms. The structure of metallic crystals is often described as a uniform distribution of atomic nuclei within a “sea” of delocalized electrons. The atoms within such a metallic solid are held together by a unique force known as metallic bonding that gives rise to many useful and varied bulk properties.
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...
02:33Lattice Centering and Coordination Number
The structure of a crystalline solid, whether a metal or not, is best described by considering its simplest repeating unit, which is referred to as its unit cell. The unit cell consists of lattice points that represent the locations of atoms or ions. The entire structure then consists of this unit cell repeating in three dimensions. The three different types of unit cells present in the cubic lattice are illustrated in Figure 1.
Types of Unit Cells
Imagine taking a large number of identical...
Types of Unit Cells
Imagine taking a large number of identical...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
01:27Lattice Energies of Ionic Crystals
Lattice energy represents the energy released when gaseous cations and anions combine to form an ionic solid, reflecting the strength of electrostatic interactions within the crystal. This process is fundamentally governed by Coulombic attraction between oppositely charged ions, where the potential energy varies inversely with the interionic distance and directly with the product of ionic charges. As ions approach one another, the electrostatic energy becomes increasingly negative, indicating a...
02:54Trends in Lattice Energy: Ion Size and Charge
An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure of the strength of this attraction. The lattice energy (ΔHlattice) of an ionic compound is defined as the energy required to separate one mole of the solid into its component gaseous ions. For the ionic solid sodium chloride, the lattice energy is the enthalpy change of the process:
01:26Imperfections in Crystal Structure: Stoichiometric Point Defects
Schottky defects arise when some lattice points in a crystal, such as those in NaCl, remain unoccupied, creating lattice vacancies without disturbing the overall electrical neutrality of the crystal. This defect is common in ionic crystals where the positive and negative ions are similar in size, as seen in sodium chloride and cesium chloride. The presence of Schottky defects enables the crystal to conduct electricity to a small extent through an ionic mechanism. Electric fields cause nearby...