Using platinum nanoparticles for catalysis research


Platinum is used in a wide variety of applications and can be found in automotive catalytic converters, drug delivery systems, electronics, medical implants and fuel cells.

High density and long life are critical characteristics for most of these applications, but it is fundamental stability and resistance to corrosion that make 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 looking for ways to improve catalytic performance while also minimizing material usage.

Platinum nanoparticles offer both improved performance and lower material costs, with over 1000x increase in active surface area, inevitably sparking the interest of researchers working in these fields.

The NL50 nanoparticle deposition system is well suited for use with heavy metals such as platinum, as it uses gas condensation to create nanoparticles in vacuum.

Because no chemicals are used in the process, the nanoparticles are also ultra-pure and do not contain any of the hydrocarbons and ligands typical of chemical synthesis.

In this article, Nikalyte highlights the properties of platinum nanoparticles made in the NL50 and discusses their suitability for use in catalyst research.

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

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

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

Experimental conditions

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

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

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

  1. Bright Field (BF) detector, which displays the straight beam and contains both Bragg-scattered and inelastic-scattered electrons.
  2. High Angle Annular Dark Field (HAADF) detector, an annular detector that can detect the atomic number and density contrast.
  3. Mid-angled annular dark field (MAADF) detector, which has the capacity to detect crystalline order variations and is valuable in crystal domain imaging.
  4. Secondary/backscattered electron (BSE) detector, which only displays 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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