Wildfire In Situ heating system enables capturing the Structural evolution of co-catalysts

Wildfire In Situ heating system enables capturing the Structural evolution of co-catalysts

Original article by Siyuan Zhang, Leo Diehl, Sina Wrede, Bettina V. Lotsch and Christina Scheu. Published in Catalysts 2020, 10, 13.

There is a pressing need to develop renewable solutions for energy conversion and storage. Photocatalysis feeds both birds by one scone, utilizing a semiconductor to harvest solar energy, and co-catalysts to convert the energy into fuels. Such photocatalytic composites are often synthesized in nanometre-size to benefit from large surface areas. Seeing the structure of these “nano-composites” is a fundamental step for rational designs toward higher catalytic activity.

Controlled Heating

In this study, scientists from the Max Planck Institute (MPIE) designed a photocatalytic nanocomposite system with an ultimately thin semiconductor – a single crystal layer of 1 nm thickness. The co-catalysts are similarly tiny, synthesized with controlled heating by a DENSsolutions Wildfire system inside a transmission electron microscope (TEM). Structural evolution of the co-catalysts is captured by in situ TEM observations, based on which a design of co-catalysts with improved photocatalytic activity was demonstrated.

Figure 1. Growth of Ni nanoparticles from the nanocomposite with 10 wt% Ni loading during in situ heating under vacuum. Scale bars in both image sets (a), (b) are 50 nm. (figure from Siyuan Zhang, Max-Planck-Institut für Eisenforschung GmbH, published in https://doi.org/10.3390/catal10010013)

The NiOx co-catalyst was generated from the Ni(OH)2 precursor using a dehydration process. The reaction is irreversible, and the nucleation of the NiOx nanoparticles occurs in a split second.
“The low bulging of the Wildfire chips allows me to keep the atomic resolution imaging with ease and observe the onset of the fast nucleation kinetics.
The latter process of nanoparticle growth is much slower and requires substantial areas for statistics. The fast and reliable temperature ramp up and quench down of the Wildfire chips enables me to monitor the structural evolution over multitudes of areas from global views to atomic resolution imaging.
Moreover, I have run these heating experiments using two generations of Wildfire chips. The sample preparation has become much easier with the new generation, as the droplet of my nanocomposite suspension can be reproducibly dried on the heating area.”
Dr. Spark (Siyuan) Zhang
Max-Planck-Institut für Eisenforschung

The mystery of x

The research is motivated by the fundamental question in materials science, the relationship between structure and properties. The reaction rate is a number to be optimised in photocatalysis. On the other hand, the structure of the studied nanocomposite is multifarious. In addition to capturing the nucleation and growth of NiOx nanoparticles, we reveal the mystery of x in the chemical composition. By repeated heat treatment protocols, nanoparticles during various stages of growth can be “frozen” for microanalysis. By electron energy loss spectroscopy and multi-variate statistical analysis (https://doi.org/10.1093/jmicro/dfx091), a metallic Ni core and an oxidized shell of NiOx is resolved.

Challenging common wisdom

With the resolution power of a modern TEM plus the accurate and stable heating provided by DENSsolutions, we can study the ultimate miniaturized nanocomposite for photocatalysis. The common wisdom to maximize surface areas of catalysts is challenged by our findings, as we exemplify improved activity from core/shell co-catalysts with sufficient spacing between them.

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Learn all about our latest Impulse release

A conversation with our Product Architect (UX) Merijn Pen.

DENSsolutions introduces the new Impulse 1.0 software. This new Impulse allows you to take complete control of your in situ TEM experiments, performed with our Wildfire, Lightning and Climate systems. We interviewed our Product Architect (UX) Merijn Pen who led the development of this new release to get all the ins and outs. 

Why was this new version of Impulse developed?

As the DENSsolutions In Situ portfolio grows, so does the number of stimuli that our users can simultaneously introduce to their sample. Each additional stimulus brings its own set of parameters that need to be controlled and monitored, which used to make running In Situ experiments increasingly complicated.
To run an experiment with our Climate system for example, the user needs to control the sample temperature and several gas condition parameters with high accuracy while simultaneously performing measurements such as calorimetry and mass spectrometry. To be able to perform such an experiment, intuitive software is needed to reduce the complexity of operation while at the same time offering full control for every individual parameter.
In order to draw meaningful conclusions, our users want to understand the influence of an individual parameter change on the process that they study. Isolating the influence of a single parameter change is only possible if you are able to reproduce the exact same experiment multiple times, meeting all the stimuli setpoints over and over again. The active involvement of the user in the operation of the stimuli can cause problems as it introduces uncontrolled variables that can lead to variation between experiments. Impulse was developed to eliminate these issues by introducing experiment automation.

What are the main benefits of this new version?

Our previous release, Impulse 0.5, already made it possible for users to perform heating and biasing experiments from a single easy-to-use interface. With this update, we have added the Gas Supply Systems and Gas Analyzer so that Climate users also benefit from complete system integration in Impulse.

The Profile Builder environment, where users can design their experiments for automation, has been upgraded with Smart Automation. This new feature guarantees reproducible experimental conditions, even for complex systems with interdependent parameters such as the Gas Supply System. Now, a single operator can perform and reproduce experiments with ease and trust the results. The possibility to automate the complete range of stimuli from one experiment profile also enables users to optimize their experimental conditions on a bench setup which saves valuable time at the TEM.

Another important feature in Impulse is the flexible dashboard that can adapt to any type of experiment and offers a complete overview in a single glance. The user can add, remove, rearrange and resize graphs to create the perfect overview. With this dashboard, users are able to quickly detect changes and draw conclusions from the data.

And lastly, the Impulse 1.0 software produces synchronized data that can easily be imported into Gatan Microscopy Suite and TVIPS software. This enables the user to quickly correlate their in situ data with the TEM images and makes it easier to create images that can be used in publications.

Who are the people that will benefit from it?

Impulse is compatible with all Wildfire, Lightning and Climate systems, so all existing users can benefit from this new release. As well as any new customer, as Impulse will be shipped with any new system sold after the 1st of June.
Some of our Wildfire and Lightning customers are already familiar with the previous release, Impulse 0.5. For those customers, the free upgrade to Impulse 1.0 brings numerous incremental improvements that were developed based on the feedback that some early users have shared with us.
Climate users will notice significant benefits from this new release. These users can now control and automate complete heating, gas and gas analyzer experiments with Impulse. Plus, there are some new features that are tailored for gas and heating experiments, such as Real-time Calorimetry and Smart Automation.

What kind of challenges were tackled during development?

One of the biggest challenges during development was improving the ease-of-use without sacrificing functionality. On the one hand, we strive to make the experiment workflow as simple as possible, on the other hand we want to offer maximum flexibility for controlling the sample conditions.
With Impulse 1.0 we have managed to combine the complete range of controls and parameters into one easy to use interface, without compromising on functionality and flexibility.

Did we cooperate with customers on this development?

Of course! Customers are at the heart of our designs so we have involved customers throughout the conceptualization, development and testing phases of Impulse. This gave us a lot of insight and, in the end, resulted in a better product.

We will continue to listen to our customers while we expand the capabilities of the Impulse platform in future developments. For this reason we have set up an online service desk at support.denssolutions.com where I invite all customers to share their feature ideas and feedback to help define the future of In Situ TEM.

What is the compatibility of Impulse 1.0?

Impulse 1.0 software is compatible with the DENSsolutions Wildfire, Lightning and Climate systems. Impulse connects to the DENSsolutions Heating Control Unit (HCU), Keithley 2450 source measuring unit (SMU), the DENSsolutions Gas Supply Systems and DENSsolutions Gas Analyzer.

Which future developments lie ahead?

The next big step will be to turn Impulse into an open platform. We will develop an open API to enable collaborations with other brands, integrations into more software platforms and advanced experiment controls through scripting.

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