Operando TEM using Climate G+ to study Metal catalyst behavior during reaction

Operando TEM using Climate G+ to study Metal catalyst behavior during reaction

by | May 26, 2020 | Catalyst research, Climate

Original article by See Wee Chee, Juan Manuel Arce-Ramos, Wenqing Li, Alexander Genest & Utkur Mirsaidov. Published in Nature Communications volume 11, Article number: 2133 (2020) .

The catalytic performance of noble metal nanoparticles (NPs) is decided by their surface structure. Hence, understanding the structural dynamics of nanoparticles during catalysis is necessary for the design of improved catalysts that can lead to significant reductions in energy consumption for industrial catalytic processes. Using the DENSsolutions Climate system, scientists from National University of Singapore (NUS) showed that they were able to capture structural changes in Palladium (Pd) NPs during CO oxidation under realistic operating environments and correlate those changes with the NPs’ catalytic activity.

The Pd NPs showed an inactive faceted structure at low temperatures which changed to an active more rounded structure at higher temperatures. This change in NP structure and activity reverses when the temperature is reduced. The reversibility of NP structural transformations has important implications for our understanding of active catalyst structures and reinforces the need for direct operando observations.

This movie was recorded during a temperature ramp from 300 to 500 °C at a rate of 2 °C/s. It clearly shows the change in the NP shape, where the flat facets and sharp corners became more rounded, which occurred concurrently with the change in catalytic activity.

Climate system

For this research, the Climate G+ system was used in combination with the DENSsolutions Gas Analyzer. The system enabled the researchers to attribute the changes in catalytic activity to the observed structural changes, which was further confirmed by thermodynamic calculations. Matching the high-resolution image sequences with outlet gas composition changes helped the authors to understand how the NP structure can influence the availability of active sites on a NP’s surface.

This research exemplifies how the different data streams from the Climate G+ (calorimetry), the Gas Analyzer (partial pressure) and the TEM detector (HR-TEM image) can be correlated into meaningful results: 

TEM detector

HR-TEM images show that the shape of the Pd NP’s in the Nano-Reactor changes from clearly faceted at 400°C to a more rounded shape at 600°C. The Pd NP’s become faceted again after the temperature was dropped to 400°C. The authors were also able to show the correlation between the morphology of the Pd NPs and their activity towards CO oxidation as function of temperature.

Calorimetry

The temperature and microcalorimetry data from the sensitive 4-point probe heater provided additional details. During the temperature ramp from 400°C to 600°C, a spike was seen at 500°C, indicating an exothermic reaction. This exothermic reaction can be interpreted as ignition of the oxidation reaction. After the spike, the Climate system measured a slight drop in heater power which further supported this conclusion. The authors were also able to match this temperature spike with the moment when the structural transitions occurred in the videos during the temperature ramps. Allowing them to correlate the onset of the reaction with the NP structure.

Gas analyzer

This onset of reaction at 500°C was further reflected as a change in gas composition, where the CO:O2 ratio in the gas flow (which was set at 1.6 by the Gas Supply System) clearly dropped and the production of CO2 concurrently increased. After a ramp-down back to 400°C the pressure ratios in the gas flow from the Nano-Reactor were restored back to their original levels, indicating de-activation.
“Our observations imply that the active structure of Pd nanoparticles is not retained outside of active catalytic conversion conditions, which will be important for interpreting results from similar studies of catalysts.
The inline mass spectrometry (Gas Analyzer) was critical for establishing the correlation between nanoparticle and catalyst activity. The low thermal drifts allow us to follow the nanoparticles during heating and cooling ramps.”
Dr. See Wee Chee
Department of Physics and Department of Biological Sciences.
National University of Singapore

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In Situ helps to understand the recovery of deactivated palladium catalyst

In Situ helps to understand the recovery of deactivated palladium catalyst

by | Apr 21, 2020 | Catalyst research, Climate

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.

Findings

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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Installing the first Climate system in Australia at the University of Sydney

Installing the first Climate system in Australia at the University of Sydney

by | Feb 27, 2020 | Climate, Partnerships

Standing next to the recently installed Climate G+ system: from left, Keita Nomoto, Lizhuo Wang and Dr. Hongwei Liu from the Australian Centre for Microscopy & Microanalysis

Recently, we celebrated the installation of the first Climate G+ system ever in Australia. For this event we interviewed Dr. Bhatia at the Australian Centre for Microscopy and Microanalysis that oversees the Sydney Microscopy and Microanalysis core research facility at the University of Sydney. Earlier, he was key in the decision to purchase the world’s first Lightning STEM stage which established his relationship with DENSsolutions and ultimately lead to the installation of the Climate G+ In Situ TEM platform.

In this interview, we discussed the research needs of his facility and how they will benefit from the solutions designed and manufactured by DENSsolutions.

Can you tell us a bit about Sydney Microscopy and Microanalysis?

Sydney Microscopy and Microanalysis is the central microscopy facility at the University of Sydney. The University of Sydney is Australia’s first university and regularly ranks in the World’s top 50 universities.

We are a multi-user facility that services both the entire university as well as people from across Australia through the Microscopy Australia access scheme. Microscopy Australia provides access to member universities throughout Australia.

This means that we need to provide highly reliable, flexible solutions as we offer our instruments to users with a broad range of applications and skill levels.

Can you give us some examples of applications that your users are involved in?

Our researchers interests are many and varied. Some of the areas that are relevant to the new Climate system include:

  • Hydrogen generation
  • Methane breakdown as a consequence of global warming
  • Environmental corrosion of metals

It is hard to know what projects it will be used for as many users haven’t even presented themselves yet. But that is the point of buying versatile equipment.

In Australia, it is normal for funding for large equipment purchases to come from research grants. Can you tell us who won the grant to acquire the Climate?

A team from the Chemical Engineering Department working on catalysts were responsible for the bulk of the funding. Their contributions from their grant were topped up by the Australian Centre for Microscopy and Microanalysis (ACMM). ACMM supports the operation of the Sydney Microscopy and Microanalysis facility.

What features of the Climate attracted you to this particular system and how do you see the DENSsolutions in situ system benefitting your research?

As a core facility working with researchers from a range of different fields we needed a system with flexibility to cater to their different interests.
Other features of the Climate that that we found attractive were the ability to interchange parts and the ease with which individual components could be replaced. The ability to perform dynamic mixing of gases provided an added degree of versatility.
All these factors contributed to what we considered to be a future-proof design that best suited our facility and the range of potential experiments of our users.
The ability to investigate dynamic processes and to be able to observe these processes in real-time was also important to us. By being able to observe the entire process takes any guesswork out of the equation and means that we don’t miss any critical steps where changes might occur.

How popular has the system been to date?

The system was only installed in November. So far, we have only had three operators and a technician trained, bearing in mind the Christmas, New Year break. We do however intend to train more operators in the near future and can see the Climate being an important research tool.

In your experience so far, how have you found the Climate system?

The installation process was quite straightforward.
The fact that the software uses the same platform as the Lightning system that we already have abbreviated the familiarisation process. The software itself is very easy to use and the system as a whole is very intuitive.
We have only performed some basic measurements so far, but are looking forward to getting into some detailed experiments in the near future.

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1st Climate holder delivers new research results at FHI Berlin

1st Climate holder delivers new research results at FHI Berlin

by | Feb 27, 2020 | Catalyst research, Climate, Materials science

Original article by Milivoj Plodinec, Hannah C. Nerl, Frank Girgsdies, Robert Schlögl and Thomas Lunkenbein. Published in ACS Catalysis.

In January 2016 DENSsolutions installed the 1st Climate holder with serial number #001 at FHI Berlin. The users at that time, Dr. Marc Willinger and Dr. Ramzi Farra, have since moved on to other institutes where they continue to use the Climate system for their research. In the mean time at FHI Berlin, new users took over the In Situ research activities and are producing excellent results with holder #001 which has since been upgraded with an EDS compatible tip.

Click here to read their recent publication in ACS Catalysis. The article demonstrates the stability of the Climate holder and Nano-Reactor. It also demonstrates the compatibility with other techniques like SAED and Mass Spectroscopy. By correlating all the data from these in situ experiments the mysteries of catalytic processes at the nanoscale will be unraveled!

“It was the combination of the DENSsolution Climate gas cell TEM holder with our homebuilt gas feed and analyzing system that enabled us to assign different parts of chemical dynamics of Pt catalyst to different activity regimes during CO Oxidation. The high sensitivity of our gas feed and analysing system ensured the detection of conversion, while the software and MEMS chip provided by DENSsolution ensured the stability over two weeks to perform experiment, even at extreme temperatures (up to 1000°C) for several hours.”

Dr. Milivoj Plodinec
Postdoc

Dr. Frank Girgsdies
Staff scientist

Dr. Thomas Lunkenbein
Group leader

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Improved insight into catalytic reduction of NOx for industrial processes

Improved insight into catalytic reduction of NOx for industrial processes

by | Oct 29, 2019 | Catalyst research, Climate, Materials science

In Situ TEM supports the design process of a new nanorod catalyst

Original article by Zhaoxia Ma, Liping Sheng, Xinwei Wang, Wentao Yuan, Shiyuan Chen, Wei Xue, Gaorong Han, Ze Zhang, Hangsheng Yang, Yunhao Lu, and Yong Wang. Published in Advanced Materials, volume 31, issue 42.

Artist impression showing growth of carbon nanotubes via an iron-catalyzed process. © 2019 DENSsolutions All Rights Reserved

There is a big opportunity for the design and development of sustainable catalysts for low-temperature NOx removal in the steel, cement and glass industries. Researchers Dr. Yong Wang et al. from Zhejiang University made a recent breakthrough using critical information obtained by In Situ TEM to design a MnOx/CeO2 nanorod (NR) catalyst with outstanding resistance to SO2 deactivation. Former studies proposed methods which succeeded in temporarily diminishing the influence of SO2 but lost their effectiveness over time. In this study, a dynamic equilibrium was achieved between sulfates formation and decomposition over the CeO2 nanorod surface, resulting in an unchanged NOx reaction rate for 1000 hours.

In Situ TEM study

Up till now, researchers have not been able to see exactly what happens to the CeO2 catalyst particle when exposed to SO2 because SO2 is so corrosive that it would damage the environmental transmission electron microscope (ETEM). Now, thanks to the DENSsolutions Climate in situ TEM Gas and Heating system, scientists can for the first time observe and record this degradation process at the atomic scale. Dr. Wang’s team found out that non-active amorphous cerium sulfates were formed from the reaction between SO2 and CeO2. The cerium sulfates formed a deposit which gradually coated the crystalline surface of the nanorods that was catalytically active.

Video 1. In situ TEM observation of the formation and evolution of cerium sulfate over Ce02 nanorods during treatment in 1000 ppm NO, 1000 ppm SO2, and 10 vol% 02 balanced with Ar at 523K. The two white arrows point to amorphous bumps at the end of Ce02 nanorods.

Video 2. In situ TEM observation of dynamic evolution of cerium sulfates during treatment in 1000 ppm NO, 1000 ppm NH3, and 10 vol% 02 balanced with Ar at 523K. The white dashed circles indicate the amorphous cerium sulfate bumps, which decomposed after the introduction of NH3.

In the first part of the In Situ TEM experiment, the researchers introduced diluted SO2 to study the deactivation behaviour of CeO2. Many obvious bumps were formed on the surface of the CeO2 nanorods (NR); this dynamic formation process can be seen in video 1. After this step, the researchers used their Climate Gas Supply System to switch off the SO2 gas flow to the TEM and switched on the diluted NH3 gas flow. The researchers could then observe the amorphous cerium sulfate bumps to become smaller and finally almost disappear at 523 K. The decomposition of the cerium sulfate bumps can be seen in video 2. This change back to polycrystalline CeO2 can be seen in detail in video 3.

Video 3. In situ TEM observation of dynamic evolution of a single cerium sulfate bump during treatment in 1000 ppm NO, 1000 ppm NH3, and 10 vol% 02 balanced with Ar at 523K. The white arrow points to amorphous cerium sulfates, which retransformed into crystalline Ce02 after the introduction of NH3.

Image 1. DENSsolutions Gas Supply System

The Gas Supply System (image 1) of the Climate G+ gas & heating system can continuously mix (dilute) gas flows from up to 3 sources. The mixing ratios for these 3 gas flows, typically 1 reducing, 1 oxidizing and 1 inert (carrier) gas, can be changed real-time between 0% and 100% according to the requirements of the in situ TEM experiment. This makes it the ideal tool for new discoveries in gas-solid interactions.

“Thanks to the state-of-the-art gas cell system from DENSsolutions, we can simply move the industrial reactions into the TEM and observe what really happens for the catalysts during reactions with atomic resolution at atmospheric pressure. This is the first time we attempted to introduce industrial gases like NH3 and SO2 to the gas cell system. To our surprise, this system was pretty robust and worked perfectly when studying the catalytic reactions involved in SO2 poisoning.”

Dr. Yong Wang – Zhejiang University

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Queen’s University Belfast joins the group of Climate In Situ users

Queen’s University Belfast joins the group of Climate In Situ users

by | Oct 24, 2019 | Chemistry, Climate, Materials science, Partnerships

Dr. Miryam Arredondo-Arechavala (centre) in front of the (packed) Climate system, together with her PhD student Tamsin O’Reilly (left) and her Postdoc Dr. Kristina Holsgrove (right).

At the beginning of October, DENSsolutions installed a Climate G system at the Queen’s University Belfast, Northern Ireland, UK. 

“We are very excited to have the Climate system in-house. It all began about 3 years ago when I started describing these new amazing holders to my colleagues in the Chemistry department. It took some time but couldn’t be happier! We are really looking forward to trying the different experiments that we have been designing for so long… Now it’s time to get to work and hopefully won’t break too many chips on the way!”
Dr. Miryam Arredondo-Arechavala

Applications

The system will be mainly used by Dr. Miryam Arredondo-Arechavala and her group to study ferroelectrics and other functional materials. Alongside this, it will help accelerate research on ionic liquids performed by the QUILL Research Centre (Queen’s University Belfast’s Ionic Liquid Laboratories) and other catalyst projects at Queen’s University Belfast.

The DENSsolutions Climate holder inserted in the Talos TEM for the first time.

The group running the first test experiment using the Climate software.

Installation and first experiment

The system was installed in less than two days by our Climate product manager Ronald Marx. After this, Marx provided hands-on training for the new group of users. The team was able to start their first In Situ Gas & Heating experiment using their own sample of Zeolite particles which was dropcasted on to the Climate Nano-Reactor. Seeing the first results created a lot of enthusiasm among the group of principal investigators and their colleagues from the chemistry department.

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