Sponsored by Nikalyte Ltd July 11, 2022 Reviewed by Olivia Frost
Platinum is used in a wide 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 features for most of these applications, but it is the fundamental stability and corrosion resistance that makes platinum ideal for use as a catalyst in fuel cells. and electrochemical batteries.
Due to the rarity and high cost of platinum, manufacturers and researchers are always looking for ways to improve catalytic performance and also to minimize material use.
Platinum nanoparticles offer improved performance and reduced material costs, with an increase of more than 1000 times the active surface, which inevitably arouses the interests of researchers working in these fields.
The NL50 nanoparticle deposition system is suitable for use with heavy metals such as platinum, as it uses finished gas condensation to create vacuum nanoparticles.
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 paper, Nikalyte highlights the properties of platinum nanoparticles created in the NL50 and discusses 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 charge (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 35.
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 size and charges were created using the NL50, changing the process parameter of the gas flow and the power of the magnetron. The parameters chosen for three different sets of samples are shown in Table 1, while Figure 1 shows the measured size distribution for each set of conditions.
Pt nanoparticles were deposited on graphene-coated carbon TEM grids (from Agar Scientific).
TEM samples were subsequently evaluated using a JEOL ARM200F instrument configured in scan mode to acquire images using four detectors:
- Bright field detector (BF), which shows the direct beam and incorporates Bragg dispersed and inelastically dispersed electrons.
- High Angle Annular Dark Field Detector (HAADF), which is an annular detector that has the ability to detect atomic number and density contrast.
- Medium angle annular dark field detector (MAADF), which has the ability to detect variations of crystalline order and is valuable for the image of crystal domains.
- Secondary / backscattered electron detector (BSE), which only shows the surface and is practical for observing the contrast and layers on the surface of nanoparticles.
Results
Figure 2 shows a TEM image of Set A and Set B Pt nanoparticles using the bright field detector. Pt nanoparticles are evenly distributed, monodisperse, and show no signs of clustering that is normally associated with chemical synthesis. Set B was coated with twice the nanoparticle charge than set A, and TEM images show increased coverage of set B without any clustering.
Figure 2. Bright field image of Pt nanoparticles of set A (left) and set B (right). Image credit: Nikalyte Ltd
Figure 3 shows 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 high contrast for high density Pt atoms.
The backscattered electron (BSE) image reveals the surface of the nanoparticles, where the crystal structure of the nanoparticles can be clearly seen, meaning a clean, pollution-free surface, such as sulfur.
Figure 3. TEM images of Set A nanoparticles using bright field detector (left), HADDF detector (center) and backscattered electron detector (right). Image credit: Nikalyte Ltd
Figure 4 shows an average HAADF image of a set of C Pt nanoparticles that has been generated by the fusion of two smaller nanoparticles in flight. The image clearly demonstrates the grain boundary and the individual crystal planes of each original nanoparticle.
Figure 4. Mean HAADF image of the nanoparticle Set C Pt. Image credit: Nikalyte Ltd
Conclusion
The TEM study of platinum nanoparticles generated in the NL50 demonstrates that nanoparticles are crystalline and free of contamination. Nanoparticles are shown to be uniform in size and distribution and not clustered.
The NL50 facilitates precise control of nanoparticle coverage for nanoparticles of a few nanometers in size. These properties are perfect for platinum catalysts where ultra-pure microscopic nanoparticles can generate high catalytic activity with a lower material load.
This information has been obtained, revised and adapted from materials provided by Nikalyte Ltd.
For more information on this source, visit Nikalyte Ltd.