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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Izasa Scientific and DENSsolutions announce new partnership

Izasa Scientific and DENSsolutions announce new partnership

by | May 6, 2020 | Partnerships

DENSsolutions is proud to partner with Izasa Scientific to serve the Spanish and Portugese market. We have been active in Spain for a number of years and in those years we started to build a good relationship with the expert and passionate team of Izasa Scientific. Now we have recently officially signed our partnership, which we are sure will benefit the TEM community in Spain and Portugal. Offering them cutting-edge In Situ technology with the best possible local support.

“During conversations and cooperation with DENSsolutions on specific projects in Spain, we became convinced about the perfect alignment between our companies. The technology offered by DENSsolutions fits perfectly with our product portfolio linked to Electron Microscopy. Now, we can offer our clients a complete on-site solution by introducing the DENSsolutions systems that complement the most advanced Electron Microscopes and direct acquisition cameras on the market.
We are convinced that the association between our companies will end in a clear benefit for the scientific community by facilitating access to the most complete solution for “in-situ” Electron Microscopy on the market. We believe that DENSsolutions is without a doubt the best partner in this field.
This good alignment, even before formalizing this agreement, which we are pleased to announce, has led to joint efforts, such as the recent webinar, which attracted considerable interest from the scientific community, and which we invite you to watch on the Izasa Scientific website.”
Carlos Arribas, General Manager at Izasa Scientific
“In the last 5 years, DENSsolutions has had the opportunity to deliver in situ heating and biasing solutions to some of the leading TEM laboratories in Spain. We also saw more and more requests for quotations for our Climate and Stream systems so we decided to start looking for a distributor in Spain and Portugal. We already had some contact with Izasa Scientific in a few projects and we got very impressed with their installed base and more importantly with the commitment of the employees of Isaza towards their customers. The core values of DENSsolutions are: “we care”, “we innovate” and “we deliver” and this is exactly what we found with the people in Izasa.
So I fully agree with Carlos Arribas, the General Manager of Isaza Scientific, when he states that there is good alignment between the two companies. It was clearly shown indeed during our joint recent webinar.
DENSsolutions will keep pushing the technology envelope for total in situ solutions based on our state of the art Nano-Chip, Nano-Reactor and Nano-Cell MEMS based sample carriers.
In order to support our customers in every part of the world, we believe that a true partnership with our distributors is extremely important and after careful consideration we decided that this true partnership for Spain and Portugal can be realized with Isaza Scientific in the most beneficial way for our customers.
Isaza Scientific brings a lot of value for DENSsolutions as they have a very extensive installed base in Spain and Portugal. But more importantly the people in Isaza Scientific really have the knowledge and drive to understand our customers’ needs.
Last but not least: with the completion of the distribution agreement with Isaza Scientific we now “cover” the whole of Europe.”
Ben Bormans, CEO -DENSsolutions

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