DENSsolutions’ Climate system takes home the Microscopy Today 2021 Innovation Award

DENSsolutions’ Climate system takes home the Microscopy Today 2021 Innovation Award

DENSsolutions becomes a consecutive two-time winner of the Microscopy Today Innovation Awards. This year, our Climate system is recognized as one of the 10 most game-changing microscopy innovations of 2021.

Just last year, our Stream system was awarded the Microscopy Today Innovation Award for its unique contribution to the field of liquid phase electron microscopy. We are honored to be taking home the same award for a second year in a row but this time for the remarkable innovation that is our Climate system. Climate is recognized as one of the 10 most game-changing microscopy innovations in 2021 by Microscopy Society of America‘s esteemed magazine, Microscopy Today. We interviewed our Chief Technology Officer Dr. Hugo Pérez-Garza, who led the development of the Climate system, to learn all about the unique benefits that made it earn such an esteemed award, as well as the development process and Climate’s current and envisioned applications. The transcript of the interview is provided below.

What was your reaction when you first heard the news?

It was pretty exciting. As you can imagine, the entire team was very happy when we first heard the news. At the end of the day, I think that this is just another consequence of the amazing teamwork that prevails in this company. And of course, to be accredited by the MSA is a big honor, especially as this is a highly esteemed award within the community. So it really means a lot to us. We really feel confident that our technology, and particularly our Climate system, will help scientists explore all sorts of new research possibilities.

What unique aspects of the system do you think made it earn such an esteemed award?

Over the last months, we have been exerting a lot of effort into making sure that we can improve the Climate system from various different angles. So that means that we have been doing a lot of work to ensure that we can optimize the different components that make up this plug-and-play system. Specifically, we have been trying to boost our MEMS capabilities (the Nano-Reactor). Moreover, we have been trying to continuously improve our hardware components, including the Gas Supply System, the Vaporizer, the Mass Spectrometer, etc. And of course, making sure that we can have new solutions as well for the software platform. Now when you put all these together, what we ended up realizing was that this new optimized Climate system brings all sort of real unique aspects to one’s research.

1) Live gas mixing

Firstly, Climate offers the possibility of performing live gas mixing (i.e. making sure that you can achieve any desired gas composition instantaneously). It ensures that users won’t have to wait for their gas mixtures to be prepared. We see this big added value in our customers’ experiments, for example in redox reactions, where the intrinsic nature of the experiment demands the possibility to quickly go from an oxidizing environment to a reducing environment. Often times people have to do this back-and-forth and in a fast and repetitive way. 

2) Start a new experiment (from a dry to wet environment or vice versa) within minutes

Furthermore, for these experiments a lot of researchers would be interested in humidifying the gas composition. This is precisely where the Vaporizer comes in. Now what happens here is that when you are humidifying the gas, often people are afraid of the contamination that the water molecules would represent for the gas lines. And that is why systems have to baked or have to undergo lengthy pumping times. But that wouldn’t be the case with the Vaporizer, as we have designed it in such a way that the introduction of the water vapor to the gas mixture is the last thing before entering the holder. So that ensures that your Gas Supply System will remain clean, and that you don’t have to perform these baking procedures or keep it pumping over night. This ultimately means you can go from a dry environment to a wet environment, or vice versa, in just a few minutes. So it opens up a lot of possibilities because it gives users this flexibility. 

3) Safely work with explosive mixtures and independently control gas parameters

The fact that we’re dealing with extremely low volumes of gas also means that we can safely handle explosive mixtures even if you plan to do this under extreme conditions such as high temperatures (above 1000°C) in combination with high pressures (i.e. 2 bars) and high relative humidity (i.e. 100%). Not only can you safely handle these explosive mixtures, but you can also control the relative humidity independently from other parameters such as temperature, pressure, gas composition and flow rate. So having this independent control also brings a lot of flexibility to users. 

4) Perform real nano-calorimetry and calibrate for time delay

The Nano-Reactor is also something very unique as we have been heavily optimizing the design such that, for example, the microheater allows for real nano-calorimetry. And this is really unique because it means that you can start quantifying and measuring the tiniest changes in temperature dissipation to understand if you’re observing an exothermic or endothermic reaction. And this is also really beneficial because you can calibrate for time delay, which is an issue that systems usually suffer from due to the unavoidable delay from the Gas Supply System to the MEMS device and to the Mass Spectrometer. Now, we can calibrate for that. 

5)  Prevent bypasses and achieve a desirable SNR

Moreover, the unique design of the Nano-Reactor itself, for which we have a patent, ensures that we can have an on-chip inlet and outlet. In other words, we can ensure that the gas will flow from the inlet to the outlet via the region of interest in a uni-directional way. And that means we can prevent bypasses and therefore improve the signal-to-noise ratio and the sensitivity of the Gas Analyzer. So the combination of these offerings (for example that our MEMS device can go to these high pressures like 2 bar, or allow you to perform EDS experiments well above 900 degrees at high pressures) ends up bringing a very unique value proposition for the user. 

What unique aspects of the system do you think made it earn such an esteemed award?

Over the last months, we have been exerting a lot of effort into making sure that we can improve the Climate system from various different angles. So that means that we have been doing a lot of work to ensure that we can optimize the different components that make up this plug-and-play system. Specifically, we have been trying to boost our MEMS capabilities (the Nano-Reactor). Moreover, we have been trying to continuously improve our hardware components, including the Gas Supply System, the Vaporizer, the Mass Spectrometer, etc. And of course, making sure that we can have new solutions as well for the software platform. Now when you put all these together, what we ended up realizing was that this new optimized Climate system brings all sort of real unique aspects to one’s research.

1) Live gas mixing

Firstly, Climate offers the possibility of performing live gas mixing (i.e. making sure that you can achieve any desired gas composition instantaneously). It ensures that users won’t have to wait for their gas mixtures to be prepared. We see this big added value in our customers’ experiments, for example in redox reactions, where the intrinsic nature of the experiment demands the possibility to quickly go from an oxidizing environment to a reducing environment. Often times people have to do this back-and-forth and in a fast and repetitive way. 

2) Start a new experiment (from a dry to wet environment or vice versa) within minutes

Furthermore, for these experiments a lot of researchers would be interested in humidifying the gas composition. This is precisely where the Vaporizer comes in. Now what happens here is that when you are humidifying the gas, often people are afraid of the contamination that the water molecules would represent for the gas lines. And that is why systems have to baked or have to undergo lengthy pumping times. But that wouldn’t be the case with the Vaporizer, as we have designed it in such a way that the introduction of the water vapor to the gas mixture is the last thing before entering the holder. So that ensures that your Gas Supply System will remain clean, and that you don’t have to perform these baking procedures or keep it pumping over night. This ultimately means you can go from a dry environment to a wet environment, or vice versa, in just a few minutes. So it opens up a lot of possibilities because it gives users this flexibility. 

3) Safely work with explosive mixtures and independently control gas parameters

The fact that we’re dealing with extremely low volumes of gas also means that we can safely handle explosive mixtures even if you plan to do this under extreme conditions such as high temperatures (above 1000°C) in combination with high pressures (i.e. 2 bars) and high relative humidity (i.e. 100%). Not only can you safely handle these explosive mixtures, but you can also control the relative humidity independently from other parameters such as temperature, pressure, gas composition and flow rate. So having this independent control also brings a lot of flexibility to users. 

4) Perform real nano-calorimetry and calibrate for time delay

The Nano-Reactor is also something very unique as we have been heavily optimizing the design such that, for example, the microheater allows for real nano-calorimetry. And this is really unique because it means that you can start quantifying and measuring the tiniest changes in temperature dissipation to understand if you’re observing an exothermic or endothermic reaction. And this is also really beneficial because you can calibrate for time delay, which is an issue that systems usually suffer from due to the unavoidable delay from the Gas Supply System to the MEMS device and to the Mass Spectrometer. Now, we can calibrate for that. 

5)  Prevent bypasses and achieve a desirable SNR

Moreover, the unique design of the Nano-Reactor itself, for which we have a patent, ensures that we can have an on-chip inlet and outlet. In other words, we can ensure that the gas will flow from the inlet to the outlet via the region of interest in a uni-directional way. And that means we can prevent bypasses and therefore improve the signal-to-noise ratio and the sensitivity of the Gas Analyzer. So the combination of these offerings (for example that our MEMS device can go to these high pressures like 2 bar, or allow you to perform EDS experiments well above 900 degrees at high pressures) ends up bringing a very unique value proposition for the user. 

What inspired you and the entire team to develop Climate in the first place?

Certainly understanding the importance and the impact that environmental studies can have on our global society was a big source of inspiration for the entire team. Having said that, understanding the solid-gas interactions at the nanoscale is what sets the foundation such that scientists can really start understanding how to optimize and synthesize future catalytic nanoparticles, which will end up playing a crucial role in applications such as carbon capture, energy storage and conversion as well as food production. So it is really this profound information that we can get from in situ TEM that gives this understanding. Because when you can start correlating particle size with composition, crystal orientation, or with the atomic or the electronic structure, it really gives a deep level of understanding for all these kinds of experiments. 

Can you walk us through the development process of Climate?

It has been 5 or 6 years since we launched our first product line for in situ gas analysis. Ever since, what we have been doing is trying to make sure that we can stay as close as we can to our customers as well as prospects. Now the intention of doing that is when you start gathering the feedback and the vision that both groups have, you start understanding the pain points a little bit more. You start becoming more empathic to their experimental needs. And that helps us identify the product profile that we should have in place. And when you are aware of this product profile, then automatically you know what technologies must be developed, which is part of your roadmap. And subsequently when you have that in place, then you also know what people and processes must be involved. So, it’s a matter of doing that so that when we gather these market requirements, we can follow a defined product creation process that will allow us to develop a technology that will match these market requirements. 

What future applications do you envision for Climate?

Certainly everything related to green technologies. As I mentioned earlier, that is a big goal and motivation that we all have at this company. So these kinds of experiments and topics I was referring to like carbon capture, energy conversion and storage, and all sort of environmental protection kind of studies, that’s really where everything will head towards. 

Thank you for reading. To learn more about our Climate system please follow the links below.

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Announcing the establishment of the DICP-DENS Microscopy Centre

Announcing the establishment of the DICP-DENS Microscopy Centre

From left to right: Wei Liu, Yu Xiao, Lijian Geng, Yan Jin, Dan Zhou, Xi Liu

We believe that it is now more important than ever to expand our efforts in enabling fundamental research in the fields of catalysis and sustainable energy. In line with the emphasis we place on multinational collaborations, we have partnered with the Dalian Institute of Chemical Physics (DICP) in China in order to accelerate these fields and achieve results together. To celebrate the establishment of the DICP-DENS in-situ electron microscopy technology application laboratory, an exciting ceremony was recently held at DICP in which numerous speakers took the stage to share their areas of expertise. 

The DICP-DENS collaborative application laboratory combines the extensive research capabilities of DICP, China’s leading and most influential catalysis research institute, with the advanced technology and outstanding research and development capabilities of DENSsolutions in the in-situ field. DENSsolutions will equip a complete Climate G+ system at the Xishan Lake Electron Microscope Center for in-situ atmosphere and heating TEM studies. The aim of this collaboration is to expand the frontiers of catalysis research and deepen our understanding of the energy conservation process. 

Opening ceremony

The event was hosted by Yan Jin, Deputy Director of the Energy Research Technology Platform of DICP. During the opening ceremony, both Yu Xiao, Director of Science and Technology Department of DICP, and Lijian Geng, Chairman and General Manager of ALTA Scientific delivered speeches.

Host Yan Jin opening the ceremony

Researcher Yu Xiao first welcomed the guests and expressed his enthusiasm about the collaboration between DICP and DENSsolutions for the realization of this application laboratory. He also relayed his hopes that this cooperation could develop in a long-term and stable manner, and that the results of this cooperation could be realized as soon as possible.

On behalf of ALTA Scientific and DENSsolutions, Lijian Geng then made an affectionate review depicting the lengthy history of the cooperation between the two parties, thanking those who made it possible. He expressed his gratitude to the many experts and professors who could not be present for the opening as well as to DENSsolutions CEO, Ben Bormans and CCO, Robert Endert for their continuous support.

Finally, DENSsolutions CTO Dr. Hugo Perez Garza delivered a digital speech, in which he expressed his excitement and gratitude on behalf of the DENSsolutions team for the trust that DICP has placed in us as a reliable partner. In his video, he signed the contract that formalizes the collaboration and expressed his confidence in a fruitful collaboration. This celebratory video is shown below.

Dr. Hugo Perez Garza delivering a digital celebratory speech 

Unveiling ceremony

After the opening event, researcher Yu Xiao, representing DICP, and Geng Lijian, representing DENSsolutions and ALTA Scientific, held an unveiling ceremony of the joint laboratory. This marked the official establishment of the DICP-DENS in-situ electron microscopy technology application laboratory.

Yu Xiao and Lijian Geng during the unveiling ceremony

Application seminar

In the second half of the conference, three speakers were invited to give talks during the application seminar. First, Professor Wei Liu gave a detailed introduction to the current configuration and construction of the Xishan Lake electron microscope platform of DICP and the team’s latest research results in the in-situ field. He also shared his thoughts and prospects on in-situ electron microscopy technology.

Next, DENSsolutions Senior Application Scientist Dr. Dan Zhou introduced in detail the leading advantages of the DENSsolutions Climate in-situ TEM gas and heating system and the latest research and development progress. She also shared some recent developments in application results.

Finally, Dr. Xi Liu from Shanghai Jiaotong University introduced his current application of in-situ aberration-corrected gas and heating TEM in heterogenous catalysis and the surface science of iron oxide reduction. He detailed the importance of the existence of in-situ TEM and explained that when combined with other characterization methods, in-situ TEM can have both super-high-resolution volume and surface characterization capabilities, thereby providing a basis for the establishment of new characterization methodology.

The three speeches during the application seminar deepened everyone’s understanding of in-situ technology and won a warm applause from the participants.

Wei Liu presenting the latest research results of the DICP research team in the in situ field

Dr. Dan Zhou giving a speech about the DENSsolutions Climate system

Xi Liu giving a speech about his current application of in situ TEM 

We are very excited to unravel the ample potential that this collaboration has in regards to advancing research in the field of catalysis and sustainable energy, and we hope to play a key role in the fight against climate change.

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Scientists find an alternate route towards CO2 reduction

Scientists find an alternate route towards CO2 reduction

In situ ETEM uncovers that deep-ultraviolet plasmons have the ability to drive endothermic reactions at room temperature

Original article by Canhui Wang, Wei-Chang D. Yang, David Raciti, Alina Bruma, Ronald Marx, Amit Agrawal and Renu Sharma

Plasmonic nanoparticles of certain metals, like gold, silver and aluminium, have the unique capability of harvesting and scattering light. These nanoparticles can harvest energy from a light source and transfer it to adsorbed gas molecules, ultimately reducing the temperature needed to drive the chemical reaction. Most of the reactions reported in research are exothermic, and only H-D bond formation has been successful at room temperature. However, for the first time in research, scientists from the NIST and IREAP in Maryland, U.S., find that endothermic reactions can be achieved at room temperature using localized surface plasmons (LSP) in the deep-UV range. Without the DENSsolutions Climate Air in situ system, this revolutionary finding would be awaiting its indispensable discovery. 

 

The DENSsolutions Climate system

When light excites the conduction electrons of certain metallic nanoparticles, it causes these electrons to undergo oscillation, generating localized surface plasmons (LSP). This resonant oscillation, called surface plasmon resonance (SPR), is essentially why these plasmonic nanoparticles have this exceptional ability to absorb and scatter light. 

In this in situ experiment, the reduction of CO₂ on a graphite sample to CO was realized at room temperature by exciting multiple LSP modes of aluminum nanoparticles using high-energy electrons. An ETEM is used to excite and characterize the aluminum LSP resonances and concurrently measure the spatial distribution of the carbon gasification around the nanoparticles in a CO₂ environment. Although this experiment took place in an ETEM, the ETEM was only used to provide an electron beam to generate the localized surface plasmons. It was the Climate Sample Holder that enabled the introduction of the CO₂ gas towards the sample.

In order to detect CO as a reaction product, the Climate Sample Holder containing the Climate Nano-Reactor was coupled to a gas chromatograph-mass spectrometer (GCMS). Four nanoreactor environments were analyzed, represented by the lines in the figure below: 1) Pure CO₂, 2) 0.01% CO added to the CO₂ gas flow, 3) Pure graphite heated at 900°C without aluminum nanoparticles, and finally 4) Illumination of aluminum on graphite in CO₂ at room temperature using an e-beam.

Detection of CO as a reaction product using the GCMS

Measurable CO was detected only in the latter three cases but not in pure CO₂. However, it was particularly in the last case where a CO-peak was realized when the electron beam was switched on to generate LSPs. Typically, a standard ETEM will produce CO concentrations that are far below the detection threshold of the GCMS. Yet, because the Climate Nano-Reactor in the Climate Sample Holder has a small volume, high pressure environment, the CO concentration in the CO₂ gas could rise high enough to enable the GCMS to detect it. This experiment demonstrates the unique stability and integrity of the Climate Nano-reactor over long periods of time. 

Novelty in findings

This novel finding not contributes highly on an academic front, paving the way for scientists to explore other industrially relevant chemical processes initiated by plasmonic fields at room temperature, but also globally by providing an alternate route for CO₂ reduction. Aluminium, Earth’s most abundant metal, presents itself as an ideal candidate for channelling energy from light to perform large-scale CO₂ reduction. This common and inexpensive metal therefore has ample potential to aid in the relentless fight against climate change.

Dr. Mihaela Albu

“The Climate Nano-Reactor proved to be essential for taking the reaction product of this LSP experiment out of the ETEM specimen chamber. Due to its unique low-volume, high-pressure design, the CO concentration in the carrier gas was still high enough to be detected ex situ.”

Ronald Marx
Senior Technical Consultant | DENSsolutions

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In-situ imaging provides detailed insights on the dynamics of SMSI induced overlayer formation on catalyst particles

In-situ imaging provides detailed insights on the dynamics of SMSI induced overlayer formation on catalyst particles

Enabled by DENSsolutions Climate system in correlation with other TEM characterization techniques

Original article by Arik Beck, Xing Huang, Luca Artiglia, Maxim Zabilskiy, Xing Wang, Przemyslaw Rzepka, Dennis Palagin, Marc-Georg Willinger & Jeroen A. van Bokhoven.

Noble metal nanoparticles stabilized on oxide supports are an important class of catalysts that are used in many applications such as fuel cells, exhaust gas treatment and energy conversion. It is well known that an interaction occurs between the nanoparticles and their oxide support which affects the catalytic activity called ‘strong metal-support interaction’ (SMSI). SMSI is a surface phenomena in which the migration of partially reduced oxide species, from the oxide support, covers the nanoparticle and thereby alters the chemisorption and catalytic properties. It can give rise to desired synergistic effects and increased selectivity. Now, using in situ TEM combined with other analytical techniques and theoretical modelling, researchers at ETH Zurich have been able to create a real time view of the SMSI phenomena.

Controlling the sample environment

Reductive pre-treatment of catalysts by heating, resulting in SMSI, has been known to alter the selectivity of oxide supported nanoparticles since the late 1970’s. However, the exact influence of the different parameters like temperature and gas concentration were still unknown. But now, thanks to the DENSsolutions Climate G+ system, researchers are able to determine the immediate effect of these parameters in increasing detail. The Climate G+ system provides a nano-reactor, containing the catalyst sample, that can be placed in any TEM* and gives the researcher unprecedented control over the sample environment in terms of temperature and gas parameters.

The in situ TEM experiments performed for this research required multiple switching between hydrogen and oxygen environments at 600 °C. This made the Climate G+ system, that is used on the JEM-ARM 300F at ETH Zurich, ideal for this research.

Evolution and dynamic structural changes of the overlayer in SMSI. A platinum particle on a titania support in the first exposure to H2 at 600 °C (a,b) and the subsequent atmosphere change to O2 at 600 °C (c), a switch to H2 (d) and then a switch to O2 again (e), and interpretation of the phenomena based on the combined results of in situ transmission electron microscopy, in situ X-ray  photoemission spectroscopy, and in situ powder X-ray diffraction (f–j). Insets for c–e show a magnified image of the overlayer structure observed. Scale bar is 5 nm.

Correlative techniques

In situ TEM, using gas and heating, is a powerful characterization technique to obtain atomistic, real time, information about the SMSI phenomena. To derive a holistic view of SMSI and the role of hydrogen and oxygen within this process. The in situ TEM results have been combined with ambient pressure XPS and in situ powder XRD experimental results. Finally, theoretical density functional theory (DFT) modelling was used to support the conclusions about how SMSI actually works.

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

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

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

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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