New Catalyst Climate Publication – ‘Capturing the Intermediate’

New Catalyst Climate Publication – ‘Capturing the Intermediate’

by | Feb 15, 2019 | Catalyst research

Intermetallics with controlled microstructure and chemical composition afford unique catalytic properties, and thus are greatly desirable for heterogeneous catalysis. Identifying the key elementary steps of intermetallic process is a key step towards mechanistic understanding and clarification.
Through the using of ideal materials, e.g., single crystalline, or reaction conditions, e.g., ultrahigh vacuum, substantial progress has been made to understand the intermetallic details, nevertheless, such material or chemical environment gap hinders insightful understanding of the real intermetallic process.
Taking the advantages of real-world pressure, gas and heating environment provided by the Climate in situ gas&heating solution, Prof. Bingsen Zhang and Prof. Dangsheng Su from Institute of Metal Research, Chinese Academy of Sciences, Prof. Wei Zhang from Jilin University and Dr. Xi Liu from Synfuels China Technology Co., Ltd., studied the details about nanoscale/atomic scale microstructure- and composition-evolution of PdZn intermetallic nanoparticles under H2 atmosphere and at elevated temperatures. They revealed the sequence of the phase transitions from Pd to PdZn via the intermediate PdHx under hydrogen atmosphere. The ability of capturing the intermediate state during the reaction condition not only discloses the microstructural information in reference to the catalyst activation in details, but also sheds light on rational design and optimum synthesis of intermetallic compound catalysts.
Related results have been accepted for publication in Angewandte Chemie International Edition.
https://onlinelibrary.wiley.com/doi/10.1002/anie.201812292

Counting atoms in operando conditions

by | Dec 18, 2018 | Catalyst research, Uncategorized

The efficiency of a catalyst relies on the capability of promoting reactions directly on its surface. Thus, there have been many attempts to accurately determine the atomic structure at the surface when gasses are flown on the catalytic sample.
Obviously, in situ electron microscopy is the best candidate to provide that answer, due to the possibility of recording ultra high resolution information while flowing gasses on the sample at high temperature. However, due to the nature of the imaging process, only 2D projections can be captured, severely limiting our understanding of the catalytic process.
Researchers at EMAT, Antwerp, have combined the high stability of the Climate in situ gas&heating solution with their multi-year experience on developing algorithms to accurately retrieve 3D structures down to atomic resolution. Platinum nanoparticles were cyclically exposed to reducing and oxidizing gas mixtures to promote and study surface re-faceting; after each step, high resolution STEM images were acquired and they were analyzed by means of a novel methodology based on deep convolutional neural networks (CNN) and molecular dynamics simulations.
 
The results show that it is now possible to obtain very accurate 3D atomic models that enable researchers to “see and count” atoms which are sitting on the surface. These new findings will allow a much deeper characterization and understanding of the processes behind catalytic reactions.
Go to Publication
Go to Climate

Experimental determination of the energy difference between competing isomers of deposited, size-selected gold nanoclusters

by | Apr 11, 2018 | Catalyst research, Chemistry, HRSTEM

In situ TEM proves once more its key role in understanding properties of real samples. We show the latest publication using a Wildfire in situ TEM heating system, published on Nature Communications, by the group of Prof. Richard Palmer.

The structure and dynamics of nano-systems are controlled by the multi-dimensional potential energy surface (PES), which describes its free energy as a function of configuration. There have been considerable theoretical efforts to determine the ground-state structures and energy differences between competing isomers of nanosytems in general and of nano clusters in particular. Gold clusters have received much theoretical attention due to the role of structure in the catalytic performance. What is needed now is an experimental handle on key parameters of the PES. Understanding the energy difference between structural isomers is important not only for the design of well-defined materials but also for understanding how these materials will work in situ. For example, if a particular structural isomer is unstable, exposure to high temperatures is likely to drive it towards the ground state (i.e. annealing), altering (for better or worse) the characteristics of the system. Such behavior is likely to be relevant to the applications of nanoparticles, which include catalysis, drug delivery and chemical sensing.

The authors have obtained the energy difference between the most abundant structural isomers of magic number Au561 clusters, the decahedron and face-centred-cubic (fcc) structures, from the equilibrium proportions of the isomers. These are measured by atomic-resolution scanning transmission electron microscopy, with an ultra-stable heating stage, as a function of temperature (125–500 °C). The publication shows clearly the benefits of DENSsolutions heating technology which provides not only ultra high mechanical and thermal stability but also across temperature control across the entire temperature range.

Wildfire in situ heating
Publication