In Situ helps to understand the recovery of deactivated palladium catalyst

In Situ helps to understand the recovery of deactivated palladium catalyst

In Situ images reveal that nanoparticles can be transformed into more active atomic species at high temperatures

Original article by Huang Zhou, Yafei Zhao, Jie Xu, Haoran Sun, Zhijun Li, Wei Liu, Tongwei Yuan, Wei Liu, Xiaoqian Wang, Weng-Chon Cheong, Zhiyuan Wang, Xin Wang, Chao Zhao, Yancai Yao, Wenyu Wang, Fangyao Zhou, Min Chen, Benjin Jin, Rongbo Sun, Jing Liu, Xun Hong, Tao Yao, Shiqiang Wei, Jun Luo & Yuen Wu. Published in Nature Communications volume 11.

Supported metal catalysts have important applications in many industrial processes like the production of chemicals, pharmaceuticals and clean fuels, and the purification of vehicle emissions. At elevated temperatures the small catalyst particles tend to form bigger particles due to a process called sintering, which decreases their active surface areas and diminishes the catalytic activity. Replacing the deactivated metal nanoparticles is a costly process. Therefore researchers are looking for ways to improve the sustainability of these catalysts. In this study, scientists from multiple Chinese institutes, including DENSsolutions customer Tianjin University of Technology, further researched a method to recover or regenerate the activity of sintered and deactivated catalysts.

Figure 1a. Clusters of Pd nanoparticles, as seen in the upper left picture, are thermally diffused in N-doped carbon layers at 900 °C under Ar atmosphere – images taken from a video. Scale bar, 5 nm.

Figure 1b. Detailed view of Pd single atoms in the N-doped carbon layers after the in situ observation in Figure 1a.


In this in situ experiment the researchers discovered that supported palladium/gold/platinum nanoparticles distributed at the interface of oxide supports and nitrogen-doped carbon shells would undergo an unexpected nitrogen-doped carbon atomization process against the sintering at high temperatures, during which the nanoparticles can be transformed into more active atomic species.

In Situ TEM study

In order to study the thermal diffusion of the Pd nanoparticles within N-doped carbon layers, a sample environment with an inert gas like Argon needs to be created. The big advantage of the Climate system is that it can create this sample environment inside a normal TEM without the need of an ETEM. Furthermore, the high stability of the Climate Nano-Reactor allowed the researchers to record the N-doped carbon atomization process with sufficient detail in order to get valuable insights.

Figure 2. Representative in-situ TEM images of Pd NPs/TiO2@PDA-Pd NPs/TiO2@C. (a-h) Different temperatures, (i-l) different times at 900 °C. Scale bar, 20 nm.

“Thanks to the wonderful gas cell system from DENSsolutions, we can directly observe and record the sintering process of metal catalysts from 100 to 900 °C under 1 bar Ar by transmission electron microscopy (TEM).
We also succeeded in tracking the N-doped carbon atomization process and the evolution of metal nanoparticles into metal single atoms. During these processes, the response of this gas cell system was very fast and perfectly stable.”

Prof. Jun Luo
Professor at the Center for Electron Microscopy, Tianjin University of Technology.

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Improved FIB lamella preparation

Improved FIB lamella preparation

A conversation with our Product Manager Dr. Yevheniy (Gin) Pivak on the new FIB stub 3.0

DENSsolutions introduces the 3rd generation of the FIB stub which enables researchers to prepare a lamella and place it directly on the Nano-Chip, all inside the FIB. In this version, many improvements were made to make the FIB sample preparation easier, safer and quicker. The development of this new stub was headed by our Product Manager Dr. Yevheniy (Gin) Pivak in close collaboration with key partners like AEM, TU Darmstadt and EMAT, Antwerp.

Why was this new FIB stub designed?

Any TEM experiment starts with a good sample either it’s a nanoparticle, a FIB lamella, 2D material or a nanowire. The FIB sample is the most complicated among others, especially when it comes to preparing lamellas onto MEMS-based Nano-Chips.
Several years back, when the users’ knowledge on FIB lamella preparation onto MEMS-based Nano-Chips was still very limited and the field itself was premature, DENSsolutions developed the first version of a FIB stub which had two inclined sides of 45 degrees on which the sample and Nano-Chip could be positioned. This stub simplified the sample preparation process by allowing the user to prepare and transfer a lamella onto the Nano-Chip in one go without breaking the vacuum of the FIB chamber, thus saving operation time. Since then version 2.0 was released, which kept the main design features like the two inclined sides but improved the sample and Nano-Chip positioning and clamping.
In the meantime, hundreds of lamellas were successfully prepared and placed onto Nano-Chips but many users still encounter challenges during the process. First of all, the issues come from an uncommon geometry that the users need to work with; the lamella preparation and the lift out need to be done at 45 and 55 stage tilt angles. On top of that, the users suffer from poor imaging, especially at low accelerating voltage and a charging effect. The positioning of the Nano-Chip and the clamping mechanism, that is also there for grounding purposes is not optimal, making the operation not very user-friendly. Because the height of the sample and the Nano-Chip on the FIB stub can differ quite a bit, there also is a safety concern.
In recent years more and more people are interested in in-situ TEM Biasing and Biasing & Heating experiments. The majority of those samples are FIB lamellas and the requirements towards the samples for electrical measurements are much stricter compared to heating experiments with various pitfalls along the way. A new approach aiming to avoid short circuiting and reiteration of biasing and biasing & heating lamellas is required.

What are the benefits of this new FIB stub?

The new FIB stub solves a number of limitations of the previous versions.

At first, the new 3.0 stub incorporates an additional flat side for placing the samples that ensures a conventional geometry and the very same and the well-known process used by any FIB operator when making and lifting out the lamella.

The revised geometry improves the quality of imaging even during the low kV milling and polishing steps. Additionally, the charging effect is reduced due to a more effective grounding of the Nano-Chips’ contact pads.

A dedicated pocket and a smart clamping mechanism is introduced which drastically simplifies and speeds up the Nano-Chip loading and unloading, making it very user-friendly. It reduces the risk of breaking the membrane when handling the Nano-Chips and there is also no need to use sticky tapes to fix or to ground the Nano-Chip, which in turn makes the process a lot cleaner.

The design of the FIB stub brings the position of the sample and the Nano-Chip to a similar eucentric height, minimizing the possibility of crashing into the pole piece, the Gas Injection System or the manipulator during the operation.

What is the compatibility of the new FIB stub?

The new FIB stub is compatible with Thermo Fisher/FEI and JEOL dual beams. It’s suitable for various models like Strata DB235 (Thermo Fisher/FEI), Helios NanoLab 600 / 650 / G4 CX (Thermo Fisher/FEI), JIB 4600F (JEOL) and many more.
It’s also suitable for any Thermo Fisher (FEI) and JEOL double tilt Heating and/or Biasing Nano-Chips.

Who are the people that will benefit from it?

Any existing customers who own a double tilt Wildfire TF(FEI)/JEOL (Wildfire D6, Wildfire H+ DT), a Lightning HB TF(FEI)/JEOL (Lightning D6+) or a Lightning HB+ TF(FEI)/JEOL (Lighting D7+, Lightning D9+) system and works with FIB lamellas will definitely benefit from the new FIB stub.
New customers of Wildfire and Lightning systems planning to work with in situ heating samples or electronic devices like non-volatile memory based on resistive switching or phase change materials, solid state batteries, solar cells, etc will enjoy the sample preparation using the 3.0 stub

What kind of challenges were tackled during development?

As in many developments, the main goal is to create a really good product that can be used by most of the users. However, because there are many dual beams from different manufacturers out there with their own stage and column design, various manipulators, workflows, details, etc. that also can vary from site to site it is quite challenging to make one generic product that is suitable for everybody. It’s not possible to fulfil everyone’s needs, but we spent a lot of time trying to get the new FIB stub as versatile as possible.
In any case, product development is a dynamic process. As long as researchers find bottlenecks in their pursuit to get the right research results, we will focus our efforts to provide them with the right solution.

Did we cooperate with customers on this development?

Any product is meant to solve customers issues and limitations or create new opportunities. We make products for our customers and not for ourselves and there is no way to make a good product without customers involvement.
Following our strategy, we involved a number of our close collaborators during the development and testing of the new FIB stub project, namely EMAT (University of Antwerp) and AEM (University of Darmstadt). Additionally, more customers from Germany, UK, Singapore, Spain, Sweden, etc. were involved in the initial discussion phase to identify the current issues and limitations with the FIB lamella preparation.

Which future developments lie ahead?

In the near future, the intention is to verify the compatibility of the FIB stub 3.0 in Zeiss, Tescan and Hitachi dual beams.
If you are a proud owner of one of above-mentioned FIBs and you would be interested to test the new stub, please contact us.
On a longer term, we are working to further improve the electrical quality of lamellas and devices prepared on biasing and heating and biasing Nano-Chips. This next development is planned to be present at the EMC 2020 conference in Copenhagen. So, stay tuned!

5 reasons to get the new FIB stub:

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