Using Platinum Nanoparticles for Catalysis Research

Platinum is used across an extensive range of applications and can be found in automotive catalytic converters, drug delivery systems, electronics, medical implants, and fuel cells.

High density and longevity are crucial characteristics for most of these applications, but it is the fundamental stability and resistance to corrosion that makes platinum ideal for use as a catalyst in fuel cells and electrochemical cells.

Due to the rarity and high cost of platinum, manufacturers and researchers are always on the lookout for ways to improve catalytic performance and also minimize material usage.

Platinum nanoparticles offer both enhanced performance and reduced material costs, with over 1000x increase in active surface area, which inevitably piques the interests of researchers working in these fields.

The NL50 nanoparticle deposition system is well-suited for use with heavy metals like platinum as it utilizes terminated gas condensation to create nanoparticles in a vacuum.

Due to the fact that no chemicals are used during the process, the nanoparticles are also ultra-pure and do not contain any of the hydrocarbons and ligands typically associated with chemical synthesis.

In this article, Nikalyte highlight the properties of platinum nanoparticles created in the NL50 and discuss their suitability for application in catalyst research.

Table 1. NL50 Deposition conditions for Pt nanoparticles. Source: Nikalyte Ltd

Sample Argon pressure (Sccm) Current (mA) Voltage (V) Power (W) Nanoparticle Loading
(ng/cm2)
Set A 10 100 426 42.6 0.3
Set B 10 100 426 42.6 0.6
Set C 40 100 426 38.8 1.5

 

Size distribution of Pt nanoparticles generated with different conditions in the NL50

Figure 1. Size distribution of Pt nanoparticles generated with different conditions in the NL50. Image Credit: Nikalyte Ltd

Experimental Conditions

Platinum (Pt) nanoparticles that vary in sizes and loadings were created using the NL50, by changing the process parameter of gas flow and magnetron power. The parameters chosen for three different sets of samples are shown in Table 1, while Figure 1 exhibits the size distribution measured for each set of conditions.

The Pt nanoparticles were deposited onto graphene-coated lacey carbon TEM grids (from Agar Scientific).

The TEM samples were subsequently evaluated using a JEOL ARM200F instrument set in scanning mode to acquire images using four detectors:

  1. Bright Field (BF) detector, which displays the straight through beam and incorporates both Bragg scattered and inelastically scattered electrons.
  2. High angle annular dark-field (HAADF) detector, which is an annular detector that has the capacity to detect the atomic number and density contrast.
  3. Medium angle annular dark field (MAADF) detector, which has the capacity to detect crystalline order variations and is valuable when imaging crystal domains.
  4. Secondary/backscattered electron (BSE) detector, which displays only the surface and is practical for observing contrast and layers on the surface of the nanoparticles.

Results

In Figure 2, a TEM image of Set A and Set B Pt nanoparticles are displayed using the bright field detector. The Pt nanoparticles are distributed uniformly, monodisperse, and display no signs of the clustering together that is typically associated with chemical synthesis. Set B was coated with twice the nanoparticle loading as Set A, and the TEM images demonstrate the increase in coverage for Set B without any clustering.

Bright Field image of set A (left) and Set B(right) Pt nanoparticles

Figure 2. Bright Field image of set A (left) and Set B(right) Pt nanoparticles. Image Credit: Nikalyte Ltd

Figure 3 exhibits TEM images of set A nanoparticles acquired using three different detectors. The nanoparticles are spherical and crystalline, as shown in the Bright Field (BF) image. As expected, the HAADF image shows a high contrast for the high-density Pt atoms.

The backscattered electron (BSE) image reveals the surface of the nanoparticles, where the crystalline structure of the nanoparticles can be seen clearly, which signifies a clean surface free of contamination, such as sulfur. 

TEM images of Set A nanoparticles using Bright field detector (left), HADDF detector (centre), and Back-scattered electron detector (right)

Figure 3. TEM images of Set A nanoparticles using Bright field detector (left), HADDF detector (center), and Back-scattered electron detector (right). Image Credit: Nikalyte Ltd

Figure 4 displays an averaged HAADF image of a set C Pt nanoparticle which has been generated by the amalgamation of two smaller nanoparticles in flight. The image clearly demonstrates the grain boundary and the individual crystal planes of each original nanoparticle. 

Averaged HAADF image of Set C Pt nanoparticle

Figure 4. Averaged HAADF image of Set C Pt nanoparticle. Image Credit: Nikalyte Ltd

Conclusion

The TEM study of Platinum nanoparticles generated in the NL50 demonstrates that the nanoparticles are crystalline and free of contamination. The nanoparticles are shown to be uniform in size and distribution and do not cluster together.

The NL50 facilitates precise control over nanoparticle coverage for nanoparticles from just a few nanometers in size. These properties are perfect for platinum catalysts where microscopic ultra-pure nanoparticles can generate high catalytic activity at a lower material loading.  

This information has been sourced, reviewed and adapted from materials provided by Nikalyte Ltd.

For more information on this source, please visit Nikalyte Ltd.

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